diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/LogicalOperatorTag.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/LogicalOperatorTag.java
index b9596be..bee4906 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/LogicalOperatorTag.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/LogicalOperatorTag.java
@@ -45,6 +45,5 @@
     INSERT_DELETE,
     INDEX_INSERT_DELETE,
     UPDATE,
-    EXTENSION_OPERATOR,
-    EXTERNAL_DATA_ACCESS_BY_RID
+    EXTENSION_OPERATOR
 }
\ No newline at end of file
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/PhysicalOperatorTag.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/PhysicalOperatorTag.java
index f166f6f..c9ef2f3 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/PhysicalOperatorTag.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/base/PhysicalOperatorTag.java
@@ -60,6 +60,5 @@
     SINGLE_PARTITION_INVERTED_INDEX_SEARCH,
     LENGTH_PARTITIONED_INVERTED_INDEX_SEARCH,
     PARTITIONINGSPLIT,
-    EXTENSION_OPERATOR,
-    EXTERNAL_ACCESS_BY_RID
+    EXTENSION_OPERATOR
 }
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/ExternalDataAccessByRIDOperator.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/ExternalDataAccessByRIDOperator.java
deleted file mode 100644
index 875c6b1..0000000
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/ExternalDataAccessByRIDOperator.java
+++ /dev/null
@@ -1,92 +0,0 @@
-/*
- * Copyright 2009-2013 by The Regents of the University of California
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * you may obtain a copy of the License from
- * 
- *     http://www.apache.org/licenses/LICENSE-2.0
- * 
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical;
-
-import java.util.List;
-
-import org.apache.commons.lang3.mutable.Mutable;
-
-import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
-import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalExpression;
-import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalOperatorTag;
-import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalVariable;
-import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.IVariableTypeEnvironment;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IOperatorSchema;
-import edu.uci.ics.hyracks.algebricks.core.algebra.properties.VariablePropagationPolicy;
-import edu.uci.ics.hyracks.algebricks.core.algebra.typing.ITypingContext;
-import edu.uci.ics.hyracks.algebricks.core.algebra.typing.NonPropagatingTypeEnvironment;
-import edu.uci.ics.hyracks.algebricks.core.algebra.visitors.ILogicalExpressionReferenceTransform;
-import edu.uci.ics.hyracks.algebricks.core.algebra.visitors.ILogicalOperatorVisitor;
-
-public class ExternalDataAccessByRIDOperator extends AbstractScanOperator{
-
-	private final List<Object> variableTypes; // TODO: get rid of this and
-	protected final Mutable<ILogicalExpression> expression;
-    
-    public ExternalDataAccessByRIDOperator(List<LogicalVariable> variables, Mutable<ILogicalExpression> expression,
-            List<Object> variableTypes) {
-        super(variables);
-        this.expression = expression;
-        this.variableTypes = variableTypes;
-    }
-
-    @Override
-    public LogicalOperatorTag getOperatorTag() {
-        return LogicalOperatorTag.EXTERNAL_DATA_ACCESS_BY_RID;
-    }
-
-    @Override
-    public IVariableTypeEnvironment computeOutputTypeEnvironment(ITypingContext ctx) throws AlgebricksException {
-        IVariableTypeEnvironment env = new NonPropagatingTypeEnvironment(ctx.getExpressionTypeComputer(), ctx.getMetadataProvider());
-            env.setVarType(variables.get(0), variableTypes.get(0));
-        return env;
-    }
-    
-    public List<Object> getVariableTypes() {
-        return variableTypes;
-    }
-    
-    @Override
-    public <R, T> R accept(ILogicalOperatorVisitor<R, T> visitor, T arg) throws AlgebricksException {
-        return visitor.visitExternalDataAccessByRIDOperator(this, arg);
-    }
-    
-    @Override
-    public boolean isMap() {
-        return false;
-    }
-    
-    @Override
-    public VariablePropagationPolicy getVariablePropagationPolicy() {
-        return new VariablePropagationPolicy() {
-            @Override
-            public void propagateVariables(IOperatorSchema target, IOperatorSchema... sources)
-                    throws AlgebricksException {
-            	target.addVariable(variables.get(0));
-            }
-        };
-    }
-
-    public Mutable<ILogicalExpression> getExpressionRef() {
-        return expression;
-    }
-    
-	@Override
-	public boolean acceptExpressionTransform(
-			ILogicalExpressionReferenceTransform visitor)
-			throws AlgebricksException {
-		return visitor.transform(expression);
-	}
-}
\ No newline at end of file
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/FDsAndEquivClassesVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/FDsAndEquivClassesVisitor.java
index c739b23..cebddee 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/FDsAndEquivClassesVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/FDsAndEquivClassesVisitor.java
@@ -50,7 +50,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -79,593 +78,572 @@
 
 public class FDsAndEquivClassesVisitor implements ILogicalOperatorVisitor<Void, IOptimizationContext> {
 
-	@Override
-	public Void visitAggregateOperator(AggregateOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		ctx.putEquivalenceClassMap(op, new HashMap<LogicalVariable, EquivalenceClass>());
-		ctx.putFDList(op, new ArrayList<FunctionalDependency>());
-		return null;
-	}
+    @Override
+    public Void visitAggregateOperator(AggregateOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        ctx.putEquivalenceClassMap(op, new HashMap<LogicalVariable, EquivalenceClass>());
+        ctx.putFDList(op, new ArrayList<FunctionalDependency>());
+        return null;
+    }
 
-	@Override
-	public Void visitAssignOperator(AssignOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		ILogicalOperator inp1 = op.getInputs().get(0).getValue();
-		Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
-		ctx.putEquivalenceClassMap(op, eqClasses);
-		List<LogicalVariable> used = new ArrayList<LogicalVariable>();
-		VariableUtilities.getUsedVariables(op, used);
-		List<FunctionalDependency> fds1 = getOrComputeFDs(inp1, ctx);
-		List<FunctionalDependency> eFds = new ArrayList<FunctionalDependency>(fds1.size());
-		for (FunctionalDependency fd : fds1) {
-			if (fd.getTail().containsAll(used)) {
-				List<LogicalVariable> hd = new ArrayList<LogicalVariable>(fd.getHead());
-				List<LogicalVariable> tl = new ArrayList<LogicalVariable>(fd.getTail());
-				tl.addAll(op.getVariables());
-				FunctionalDependency fd2 = new FunctionalDependency(hd, tl);
-				eFds.add(fd2);
-			} else {
-				eFds.add(fd);
-			}
-		}
-		ctx.putFDList(op, eFds);
-		return null;
-	}
+    @Override
+    public Void visitAssignOperator(AssignOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        ILogicalOperator inp1 = op.getInputs().get(0).getValue();
+        Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
+        ctx.putEquivalenceClassMap(op, eqClasses);
+        List<LogicalVariable> used = new ArrayList<LogicalVariable>();
+        VariableUtilities.getUsedVariables(op, used);
+        List<FunctionalDependency> fds1 = getOrComputeFDs(inp1, ctx);
+        List<FunctionalDependency> eFds = new ArrayList<FunctionalDependency>(fds1.size());
+        for (FunctionalDependency fd : fds1) {
+            if (fd.getTail().containsAll(used)) {
+                List<LogicalVariable> hd = new ArrayList<LogicalVariable>(fd.getHead());
+                List<LogicalVariable> tl = new ArrayList<LogicalVariable>(fd.getTail());
+                tl.addAll(op.getVariables());
+                FunctionalDependency fd2 = new FunctionalDependency(hd, tl);
+                eFds.add(fd2);
+            } else {
+                eFds.add(fd);
+            }
+        }
+        ctx.putFDList(op, eFds);
+        return null;
+    }
 
-	@Override
-	public Void visitDataScanOperator(DataSourceScanOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		ILogicalOperator inp1 = op.getInputs().get(0).getValue();
-		Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
-		ctx.putEquivalenceClassMap(op, eqClasses);
-		List<FunctionalDependency> fds = new ArrayList<FunctionalDependency>(getOrComputeFDs(inp1, ctx));
-		ctx.putFDList(op, fds);
-		op.getDataSource().computeFDs(op.getVariables(), fds);
-		return null;
-	}
+    @Override
+    public Void visitDataScanOperator(DataSourceScanOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        ILogicalOperator inp1 = op.getInputs().get(0).getValue();
+        Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
+        ctx.putEquivalenceClassMap(op, eqClasses);
+        List<FunctionalDependency> fds = new ArrayList<FunctionalDependency>(getOrComputeFDs(inp1, ctx));
+        ctx.putFDList(op, fds);
+        op.getDataSource().computeFDs(op.getVariables(), fds);
+        return null;
+    }
 
-	@Override
-	public Void visitDistinctOperator(DistinctOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		ILogicalOperator op0 = op.getInputs().get(0).getValue();
-		List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
-		ctx.putFDList(op, functionalDependencies);
-		for (FunctionalDependency inherited : getOrComputeFDs(op0, ctx)) {
-			boolean isCoveredByDistinctByVars = true;
-			for (LogicalVariable v : inherited.getHead()) {
-				if (!op.isDistinctByVar(v)) {
-					isCoveredByDistinctByVars = false;
-				}
-			}
-			if (isCoveredByDistinctByVars) {
-				List<LogicalVariable> newTail = new ArrayList<LogicalVariable>();
-				for (LogicalVariable v2 : inherited.getTail()) {
-					if (op.isDistinctByVar(v2)) {
-						newTail.add(v2);
-					}
-				}
-				if (!newTail.isEmpty()) {
-					List<LogicalVariable> newHead = new ArrayList<LogicalVariable>(inherited.getHead());
-					FunctionalDependency newFd = new FunctionalDependency(newHead, newTail);
-					functionalDependencies.add(newFd);
-				}
-			}
-		}
-		Set<LogicalVariable> gbySet = new HashSet<LogicalVariable>();
-		List<Mutable<ILogicalExpression>> expressions = op.getExpressions();
-		for (Mutable<ILogicalExpression> pRef : expressions) {
-			ILogicalExpression p = pRef.getValue();
-			if (p.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
-				VariableReferenceExpression v = (VariableReferenceExpression) p;
-				gbySet.add(v.getVariableReference());
-			}
-		}
-		LocalGroupingProperty lgp = new LocalGroupingProperty(gbySet);
+    @Override
+    public Void visitDistinctOperator(DistinctOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        ILogicalOperator op0 = op.getInputs().get(0).getValue();
+        List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
+        ctx.putFDList(op, functionalDependencies);
+        for (FunctionalDependency inherited : getOrComputeFDs(op0, ctx)) {
+            boolean isCoveredByDistinctByVars = true;
+            for (LogicalVariable v : inherited.getHead()) {
+                if (!op.isDistinctByVar(v)) {
+                    isCoveredByDistinctByVars = false;
+                }
+            }
+            if (isCoveredByDistinctByVars) {
+                List<LogicalVariable> newTail = new ArrayList<LogicalVariable>();
+                for (LogicalVariable v2 : inherited.getTail()) {
+                    if (op.isDistinctByVar(v2)) {
+                        newTail.add(v2);
+                    }
+                }
+                if (!newTail.isEmpty()) {
+                    List<LogicalVariable> newHead = new ArrayList<LogicalVariable>(inherited.getHead());
+                    FunctionalDependency newFd = new FunctionalDependency(newHead, newTail);
+                    functionalDependencies.add(newFd);
+                }
+            }
+        }
+        Set<LogicalVariable> gbySet = new HashSet<LogicalVariable>();
+        List<Mutable<ILogicalExpression>> expressions = op.getExpressions();
+        for (Mutable<ILogicalExpression> pRef : expressions) {
+            ILogicalExpression p = pRef.getValue();
+            if (p.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
+                VariableReferenceExpression v = (VariableReferenceExpression) p;
+                gbySet.add(v.getVariableReference());
+            }
+        }
+        LocalGroupingProperty lgp = new LocalGroupingProperty(gbySet);
 
-		Map<LogicalVariable, EquivalenceClass> equivalenceClasses = getOrComputeEqClasses(op0, ctx);
-		ctx.putEquivalenceClassMap(op, equivalenceClasses);
+        Map<LogicalVariable, EquivalenceClass> equivalenceClasses = getOrComputeEqClasses(op0, ctx);
+        ctx.putEquivalenceClassMap(op, equivalenceClasses);
 
-		lgp.normalizeGroupingColumns(equivalenceClasses, functionalDependencies);
-		Set<LogicalVariable> normSet = lgp.getColumnSet();
-		List<Mutable<ILogicalExpression>> newDistinctByList = new ArrayList<Mutable<ILogicalExpression>>();
-		for (Mutable<ILogicalExpression> p2Ref : expressions) {
-			ILogicalExpression p2 = p2Ref.getValue();
-			if (p2.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
-				VariableReferenceExpression var2 = (VariableReferenceExpression) p2;
-				LogicalVariable v2 = var2.getVariableReference();
-				if (normSet.contains(v2)) {
-					newDistinctByList.add(p2Ref);
-				}
-			} else {
-				newDistinctByList.add(p2Ref);
-			}
-		}
-		expressions.clear();
-		expressions.addAll(newDistinctByList);
-		return null;
-	}
+        lgp.normalizeGroupingColumns(equivalenceClasses, functionalDependencies);
+        Set<LogicalVariable> normSet = lgp.getColumnSet();
+        List<Mutable<ILogicalExpression>> newDistinctByList = new ArrayList<Mutable<ILogicalExpression>>();
+        for (Mutable<ILogicalExpression> p2Ref : expressions) {
+            ILogicalExpression p2 = p2Ref.getValue();
+            if (p2.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
+                VariableReferenceExpression var2 = (VariableReferenceExpression) p2;
+                LogicalVariable v2 = var2.getVariableReference();
+                if (normSet.contains(v2)) {
+                    newDistinctByList.add(p2Ref);
+                }
+            } else {
+                newDistinctByList.add(p2Ref);
+            }
+        }
+        expressions.clear();
+        expressions.addAll(newDistinctByList);
+        return null;
+    }
 
-	@Override
-	public Void visitEmptyTupleSourceOperator(EmptyTupleSourceOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		ctx.putEquivalenceClassMap(op, new HashMap<LogicalVariable, EquivalenceClass>());
-		ctx.putFDList(op, new ArrayList<FunctionalDependency>());
-		return null;
-	}
+    @Override
+    public Void visitEmptyTupleSourceOperator(EmptyTupleSourceOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        ctx.putEquivalenceClassMap(op, new HashMap<LogicalVariable, EquivalenceClass>());
+        ctx.putFDList(op, new ArrayList<FunctionalDependency>());
+        return null;
+    }
 
-	@Override
-	public Void visitExchangeOperator(ExchangeOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		propagateFDsAndEquivClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitExchangeOperator(ExchangeOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        propagateFDsAndEquivClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitGroupByOperator(GroupByOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
-		List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
-		ctx.putEquivalenceClassMap(op, equivalenceClasses);
-		ctx.putFDList(op, functionalDependencies);
+    @Override
+    public Void visitGroupByOperator(GroupByOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
+        List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
+        ctx.putEquivalenceClassMap(op, equivalenceClasses);
+        ctx.putFDList(op, functionalDependencies);
 
-		List<FunctionalDependency> inheritedFDs = new ArrayList<FunctionalDependency>();
-		for (ILogicalPlan p : op.getNestedPlans()) {
-			for (Mutable<ILogicalOperator> r : p.getRoots()) {
-				ILogicalOperator op2 = r.getValue();
-				equivalenceClasses.putAll(getOrComputeEqClasses(op2, ctx));
-				inheritedFDs.addAll(getOrComputeFDs(op2, ctx));
-			}
-		}
+        List<FunctionalDependency> inheritedFDs = new ArrayList<FunctionalDependency>();
+        for (ILogicalPlan p : op.getNestedPlans()) {
+            for (Mutable<ILogicalOperator> r : p.getRoots()) {
+                ILogicalOperator op2 = r.getValue();
+                equivalenceClasses.putAll(getOrComputeEqClasses(op2, ctx));
+                inheritedFDs.addAll(getOrComputeFDs(op2, ctx));
+            }
+        }
 
-		ILogicalOperator op0 = op.getInputs().get(0).getValue();
-		inheritedFDs.addAll(getOrComputeFDs(op0, ctx));
-		Map<LogicalVariable, EquivalenceClass> inheritedEcs = getOrComputeEqClasses(op0, ctx);
-		for (FunctionalDependency inherited : inheritedFDs) {
-			boolean isCoveredByGbyOrDecorVars = true;
-			List<LogicalVariable> newHead = new ArrayList<LogicalVariable>(inherited.getHead().size());
-			for (LogicalVariable v : inherited.getHead()) {
-				LogicalVariable vnew = getNewGbyVar(op, v);
-				if (vnew == null) {
-					vnew = getNewDecorVar(op, v);
-					if (vnew == null) {
-						isCoveredByGbyOrDecorVars = false;
-					}
-					break;
-				}
-				newHead.add(vnew);
-			}
+        ILogicalOperator op0 = op.getInputs().get(0).getValue();
+        inheritedFDs.addAll(getOrComputeFDs(op0, ctx));
+        Map<LogicalVariable, EquivalenceClass> inheritedEcs = getOrComputeEqClasses(op0, ctx);
+        for (FunctionalDependency inherited : inheritedFDs) {
+            boolean isCoveredByGbyOrDecorVars = true;
+            List<LogicalVariable> newHead = new ArrayList<LogicalVariable>(inherited.getHead().size());
+            for (LogicalVariable v : inherited.getHead()) {
+                LogicalVariable vnew = getNewGbyVar(op, v);
+                if (vnew == null) {
+                    vnew = getNewDecorVar(op, v);
+                    if (vnew == null) {
+                        isCoveredByGbyOrDecorVars = false;
+                    }
+                    break;
+                }
+                newHead.add(vnew);
+            }
 
-			if (isCoveredByGbyOrDecorVars) {
-				List<LogicalVariable> newTail = new ArrayList<LogicalVariable>();
-				for (LogicalVariable v2 : inherited.getTail()) {
-					LogicalVariable v3 = getNewGbyVar(op, v2);
-					if (v3 != null) {
-						newTail.add(v3);
-					}
-				}
-				if (!newTail.isEmpty()) {
-					FunctionalDependency newFd = new FunctionalDependency(newHead, newTail);
-					functionalDependencies.add(newFd);
-				}
-			}
-		}
+            if (isCoveredByGbyOrDecorVars) {
+                List<LogicalVariable> newTail = new ArrayList<LogicalVariable>();
+                for (LogicalVariable v2 : inherited.getTail()) {
+                    LogicalVariable v3 = getNewGbyVar(op, v2);
+                    if (v3 != null) {
+                        newTail.add(v3);
+                    }
+                }
+                if (!newTail.isEmpty()) {
+                    FunctionalDependency newFd = new FunctionalDependency(newHead, newTail);
+                    functionalDependencies.add(newFd);
+                }
+            }
+        }
 
-		List<LogicalVariable> premiseGby = new LinkedList<LogicalVariable>();
-		List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> gByList = op.getGroupByList();
-		for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gByList) {
-			premiseGby.add(p.first);
-		}
+        List<LogicalVariable> premiseGby = new LinkedList<LogicalVariable>();
+        List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> gByList = op.getGroupByList();
+        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gByList) {
+            premiseGby.add(p.first);
+        }
 
-		List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> decorList = op.getDecorList();
+        List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> decorList = op.getDecorList();
 
-		LinkedList<LogicalVariable> conclDecor = new LinkedList<LogicalVariable>();
-		for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : decorList) {
-			conclDecor.add(GroupByOperator.getDecorVariable(p));
-		}
-		if (!conclDecor.isEmpty()) {
-			functionalDependencies.add(new FunctionalDependency(premiseGby, conclDecor));
-		}
+        LinkedList<LogicalVariable> conclDecor = new LinkedList<LogicalVariable>();
+        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : decorList) {
+            conclDecor.add(GroupByOperator.getDecorVariable(p));
+        }
+        if (!conclDecor.isEmpty()) {
+            functionalDependencies.add(new FunctionalDependency(premiseGby, conclDecor));
+        }
 
-		Set<LogicalVariable> gbySet = new HashSet<LogicalVariable>();
-		for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gByList) {
-			ILogicalExpression expr = p.second.getValue();
-			if (expr.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
-				VariableReferenceExpression v = (VariableReferenceExpression) expr;
-				gbySet.add(v.getVariableReference());
-			}
-		}
-		LocalGroupingProperty lgp = new LocalGroupingProperty(gbySet);
-		lgp.normalizeGroupingColumns(inheritedEcs, inheritedFDs);
-		Set<LogicalVariable> normSet = lgp.getColumnSet();
-		List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> newGbyList = new ArrayList<Pair<LogicalVariable, Mutable<ILogicalExpression>>>();
-		boolean changed = false;
-		for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gByList) {
-			ILogicalExpression expr = p.second.getValue();
-			if (expr.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
-				VariableReferenceExpression varRef = (VariableReferenceExpression) expr;
-				LogicalVariable v2 = varRef.getVariableReference();
-				EquivalenceClass ec2 = inheritedEcs.get(v2);
-				LogicalVariable v3;
-				if (ec2 != null && !ec2.representativeIsConst()) {
-					v3 = ec2.getVariableRepresentative();
-				} else {
-					v3 = v2;
-				}
-				if (normSet.contains(v3)) {
-					newGbyList.add(p);
-				} else {
-					changed = true;
-					decorList.add(p);
-				}
-			} else {
-				newGbyList.add(p);
-			}
-		}
-		if (changed) {
-			AlgebricksConfig.ALGEBRICKS_LOGGER.fine(">>>> Group-by list changed from "
-					+ GroupByOperator.veListToString(gByList) + " to " + GroupByOperator.veListToString(newGbyList)
-					+ ".\n");
-		}
-		gByList.clear();
-		gByList.addAll(newGbyList);
-		return null;
-	}
+        Set<LogicalVariable> gbySet = new HashSet<LogicalVariable>();
+        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gByList) {
+            ILogicalExpression expr = p.second.getValue();
+            if (expr.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
+                VariableReferenceExpression v = (VariableReferenceExpression) expr;
+                gbySet.add(v.getVariableReference());
+            }
+        }
+        LocalGroupingProperty lgp = new LocalGroupingProperty(gbySet);
+        lgp.normalizeGroupingColumns(inheritedEcs, inheritedFDs);
+        Set<LogicalVariable> normSet = lgp.getColumnSet();
+        List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> newGbyList = new ArrayList<Pair<LogicalVariable, Mutable<ILogicalExpression>>>();
+        boolean changed = false;
+        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gByList) {
+            ILogicalExpression expr = p.second.getValue();
+            if (expr.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
+                VariableReferenceExpression varRef = (VariableReferenceExpression) expr;
+                LogicalVariable v2 = varRef.getVariableReference();
+                EquivalenceClass ec2 = inheritedEcs.get(v2);
+                LogicalVariable v3;
+                if (ec2 != null && !ec2.representativeIsConst()) {
+                    v3 = ec2.getVariableRepresentative();
+                } else {
+                    v3 = v2;
+                }
+                if (normSet.contains(v3)) {
+                    newGbyList.add(p);
+                } else {
+                    changed = true;
+                    decorList.add(p);
+                }
+            } else {
+                newGbyList.add(p);
+            }
+        }
+        if (changed) {
+            AlgebricksConfig.ALGEBRICKS_LOGGER.fine(">>>> Group-by list changed from "
+                    + GroupByOperator.veListToString(gByList) + " to " + GroupByOperator.veListToString(newGbyList)
+                    + ".\n");
+        }
+        gByList.clear();
+        gByList.addAll(newGbyList);
+        return null;
+    }
 
-	@Override
-	public Void visitInnerJoinOperator(InnerJoinOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
-		List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
-		ctx.putEquivalenceClassMap(op, equivalenceClasses);
-		ctx.putFDList(op, functionalDependencies);
-		ILogicalOperator op0 = op.getInputs().get(0).getValue();
-		ILogicalOperator op1 = op.getInputs().get(1).getValue();
-		functionalDependencies.addAll(getOrComputeFDs(op0, ctx));
-		functionalDependencies.addAll(getOrComputeFDs(op1, ctx));
-		equivalenceClasses.putAll(getOrComputeEqClasses(op0, ctx));
-		equivalenceClasses.putAll(getOrComputeEqClasses(op1, ctx));
-		ILogicalExpression expr = op.getCondition().getValue();
-		expr.getConstraintsAndEquivClasses(functionalDependencies, equivalenceClasses);
-		return null;
-	}
+    @Override
+    public Void visitInnerJoinOperator(InnerJoinOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
+        List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
+        ctx.putEquivalenceClassMap(op, equivalenceClasses);
+        ctx.putFDList(op, functionalDependencies);
+        ILogicalOperator op0 = op.getInputs().get(0).getValue();
+        ILogicalOperator op1 = op.getInputs().get(1).getValue();
+        functionalDependencies.addAll(getOrComputeFDs(op0, ctx));
+        functionalDependencies.addAll(getOrComputeFDs(op1, ctx));
+        equivalenceClasses.putAll(getOrComputeEqClasses(op0, ctx));
+        equivalenceClasses.putAll(getOrComputeEqClasses(op1, ctx));
+        ILogicalExpression expr = op.getCondition().getValue();
+        expr.getConstraintsAndEquivClasses(functionalDependencies, equivalenceClasses);
+        return null;
+    }
 
-	@Override
-	public Void visitLeftOuterJoinOperator(LeftOuterJoinOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
-		List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
-		ctx.putEquivalenceClassMap(op, equivalenceClasses);
-		ctx.putFDList(op, functionalDependencies);
-		ILogicalOperator opLeft = op.getInputs().get(0).getValue();
-		ILogicalOperator opRight = op.getInputs().get(1).getValue();
-		functionalDependencies.addAll(getOrComputeFDs(opLeft, ctx));
-		functionalDependencies.addAll(getOrComputeFDs(opRight, ctx));
-		equivalenceClasses.putAll(getOrComputeEqClasses(opLeft, ctx));
-		equivalenceClasses.putAll(getOrComputeEqClasses(opRight, ctx));
+    @Override
+    public Void visitLeftOuterJoinOperator(LeftOuterJoinOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
+        List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
+        ctx.putEquivalenceClassMap(op, equivalenceClasses);
+        ctx.putFDList(op, functionalDependencies);
+        ILogicalOperator opLeft = op.getInputs().get(0).getValue();
+        ILogicalOperator opRight = op.getInputs().get(1).getValue();
+        functionalDependencies.addAll(getOrComputeFDs(opLeft, ctx));
+        functionalDependencies.addAll(getOrComputeFDs(opRight, ctx));
+        equivalenceClasses.putAll(getOrComputeEqClasses(opLeft, ctx));
+        equivalenceClasses.putAll(getOrComputeEqClasses(opRight, ctx));
 
-		Collection<LogicalVariable> leftSideVars;
-		if (opLeft.getSchema() == null) {
-			leftSideVars = new LinkedList<LogicalVariable>();
-			VariableUtilities.getLiveVariables(opLeft, leftSideVars);
-			// actually, not all produced vars. are visible (due to projection)
-			// so using cached schema is better and faster
-		} else {
-			leftSideVars = opLeft.getSchema();
-		}
-		ILogicalExpression expr = op.getCondition().getValue();
-		expr.getConstraintsForOuterJoin(functionalDependencies, leftSideVars);
-		return null;
-	}
+        Collection<LogicalVariable> leftSideVars;
+        if (opLeft.getSchema() == null) {
+            leftSideVars = new LinkedList<LogicalVariable>();
+            VariableUtilities.getLiveVariables(opLeft, leftSideVars);
+            // actually, not all produced vars. are visible (due to projection)
+            // so using cached schema is better and faster
+        } else {
+            leftSideVars = opLeft.getSchema();
+        }
+        ILogicalExpression expr = op.getCondition().getValue();
+        expr.getConstraintsForOuterJoin(functionalDependencies, leftSideVars);
+        return null;
+    }
 
-	@Override
-	public Void visitLimitOperator(LimitOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		propagateFDsAndEquivClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitLimitOperator(LimitOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        propagateFDsAndEquivClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitNestedTupleSourceOperator(NestedTupleSourceOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		AbstractLogicalOperator op1 = (AbstractLogicalOperator) op.getDataSourceReference().getValue();
-		ILogicalOperator inp1 = op1.getInputs().get(0).getValue();
-		Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
-		ctx.putEquivalenceClassMap(op, eqClasses);
-		List<FunctionalDependency> fds = new ArrayList<FunctionalDependency>(getOrComputeFDs(inp1, ctx));
-		if (op1.getOperatorTag() == LogicalOperatorTag.GROUP) {
-			GroupByOperator gby = (GroupByOperator) op1;
-			LinkedList<LogicalVariable> tail = new LinkedList<LogicalVariable>();
-			for (LogicalVariable v : gby.getGbyVarList()) {
-				tail.add(v);
-				// all values for gby vars. are the same
-			}
-			FunctionalDependency gbyfd = new FunctionalDependency(new LinkedList<LogicalVariable>(), tail);
-			fds.add(gbyfd);
-		}
-		ctx.putFDList(op, fds);
-		return null;
-	}
+    @Override
+    public Void visitNestedTupleSourceOperator(NestedTupleSourceOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        AbstractLogicalOperator op1 = (AbstractLogicalOperator) op.getDataSourceReference().getValue();
+        ILogicalOperator inp1 = op1.getInputs().get(0).getValue();
+        Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
+        ctx.putEquivalenceClassMap(op, eqClasses);
+        List<FunctionalDependency> fds = new ArrayList<FunctionalDependency>(getOrComputeFDs(inp1, ctx));
+        if (op1.getOperatorTag() == LogicalOperatorTag.GROUP) {
+            GroupByOperator gby = (GroupByOperator) op1;
+            LinkedList<LogicalVariable> tail = new LinkedList<LogicalVariable>();
+            for (LogicalVariable v : gby.getGbyVarList()) {
+                tail.add(v);
+                // all values for gby vars. are the same
+            }
+            FunctionalDependency gbyfd = new FunctionalDependency(new LinkedList<LogicalVariable>(), tail);
+            fds.add(gbyfd);
+        }
+        ctx.putFDList(op, fds);
+        return null;
+    }
 
-	@Override
-	public Void visitOrderOperator(OrderOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		propagateFDsAndEquivClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitOrderOperator(OrderOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        propagateFDsAndEquivClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitPartitioningSplitOperator(PartitioningSplitOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		throw new NotImplementedException();
-	}
+    @Override
+    public Void visitPartitioningSplitOperator(PartitioningSplitOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        throw new NotImplementedException();
+    }
 
-	@Override
-	public Void visitProjectOperator(ProjectOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		propagateFDsAndEquivClassesForUsedVars(op, ctx, op.getVariables());
-		return null;
-	}
+    @Override
+    public Void visitProjectOperator(ProjectOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        propagateFDsAndEquivClassesForUsedVars(op, ctx, op.getVariables());
+        return null;
+    }
 
-	@Override
-	public Void visitReplicateOperator(ReplicateOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		propagateFDsAndEquivClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitReplicateOperator(ReplicateOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        propagateFDsAndEquivClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitRunningAggregateOperator(RunningAggregateOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		propagateFDsAndEquivClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitRunningAggregateOperator(RunningAggregateOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        propagateFDsAndEquivClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitScriptOperator(ScriptOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		propagateFDsAndEquivClassesForUsedVars(op, ctx, op.getInputVariables());
-		return null;
-	}
+    @Override
+    public Void visitScriptOperator(ScriptOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        propagateFDsAndEquivClassesForUsedVars(op, ctx, op.getInputVariables());
+        return null;
+    }
 
-	@Override
-	public Void visitSelectOperator(SelectOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
-		List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
-		ctx.putEquivalenceClassMap(op, equivalenceClasses);
-		ctx.putFDList(op, functionalDependencies);
-		ILogicalOperator op0 = op.getInputs().get(0).getValue();
-		functionalDependencies.addAll(getOrComputeFDs(op0, ctx));
-		equivalenceClasses.putAll(getOrComputeEqClasses(op0, ctx));
-		ILogicalExpression expr = op.getCondition().getValue();
-		expr.getConstraintsAndEquivClasses(functionalDependencies, equivalenceClasses);
-		return null;
-	}
+    @Override
+    public Void visitSelectOperator(SelectOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
+        List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
+        ctx.putEquivalenceClassMap(op, equivalenceClasses);
+        ctx.putFDList(op, functionalDependencies);
+        ILogicalOperator op0 = op.getInputs().get(0).getValue();
+        functionalDependencies.addAll(getOrComputeFDs(op0, ctx));
+        equivalenceClasses.putAll(getOrComputeEqClasses(op0, ctx));
+        ILogicalExpression expr = op.getCondition().getValue();
+        expr.getConstraintsAndEquivClasses(functionalDependencies, equivalenceClasses);
+        return null;
+    }
 
-	@Override
-	public Void visitSubplanOperator(SubplanOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
-		List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
-		ctx.putEquivalenceClassMap(op, equivalenceClasses);
-		ctx.putFDList(op, functionalDependencies);
-		for (ILogicalPlan p : op.getNestedPlans()) {
-			for (Mutable<ILogicalOperator> r : p.getRoots()) {
-				ILogicalOperator op2 = r.getValue();
-				equivalenceClasses.putAll(getOrComputeEqClasses(op2, ctx));
-				functionalDependencies.addAll(getOrComputeFDs(op2, ctx));
-			}
-		}
-		return null;
-	}
+    @Override
+    public Void visitSubplanOperator(SubplanOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
+        List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
+        ctx.putEquivalenceClassMap(op, equivalenceClasses);
+        ctx.putFDList(op, functionalDependencies);
+        for (ILogicalPlan p : op.getNestedPlans()) {
+            for (Mutable<ILogicalOperator> r : p.getRoots()) {
+                ILogicalOperator op2 = r.getValue();
+                equivalenceClasses.putAll(getOrComputeEqClasses(op2, ctx));
+                functionalDependencies.addAll(getOrComputeFDs(op2, ctx));
+            }
+        }
+        return null;
+    }
 
-	@Override
-	public Void visitUnionOperator(UnionAllOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		setEmptyFDsEqClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitUnionOperator(UnionAllOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        setEmptyFDsEqClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitUnnestMapOperator(UnnestMapOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		fdsEqClassesForAbstractUnnestOperator(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitUnnestMapOperator(UnnestMapOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        fdsEqClassesForAbstractUnnestOperator(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitExternalDataAccessByRIDOperator(ExternalDataAccessByRIDOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		fdsEqClassesForExternalAccessOperator(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitUnnestOperator(UnnestOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        fdsEqClassesForAbstractUnnestOperator(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitUnnestOperator(UnnestOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		fdsEqClassesForAbstractUnnestOperator(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitWriteOperator(WriteOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        // propagateFDsAndEquivClasses(op, ctx);
+        setEmptyFDsEqClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitWriteOperator(WriteOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		// propagateFDsAndEquivClasses(op, ctx);
-		setEmptyFDsEqClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitDistributeResultOperator(DistributeResultOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        // propagateFDsAndEquivClasses(op, ctx);
+        setEmptyFDsEqClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitDistributeResultOperator(DistributeResultOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		// propagateFDsAndEquivClasses(op, ctx);
-		setEmptyFDsEqClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitWriteResultOperator(WriteResultOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        // propagateFDsAndEquivClasses(op, ctx);
+        setEmptyFDsEqClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitWriteResultOperator(WriteResultOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		// propagateFDsAndEquivClasses(op, ctx);
-		setEmptyFDsEqClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitInsertDeleteOperator(InsertDeleteOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        setEmptyFDsEqClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitInsertDeleteOperator(InsertDeleteOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		setEmptyFDsEqClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitIndexInsertDeleteOperator(IndexInsertDeleteOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        setEmptyFDsEqClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitIndexInsertDeleteOperator(IndexInsertDeleteOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		setEmptyFDsEqClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitSinkOperator(SinkOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        setEmptyFDsEqClasses(op, ctx);
+        return null;
+    }
 
-	@Override
-	public Void visitSinkOperator(SinkOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		setEmptyFDsEqClasses(op, ctx);
-		return null;
-	}
+    private void propagateFDsAndEquivClasses(ILogicalOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        ILogicalOperator inp1 = op.getInputs().get(0).getValue();
+        Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
+        ctx.putEquivalenceClassMap(op, eqClasses);
+        List<FunctionalDependency> fds = getOrComputeFDs(inp1, ctx);
+        ctx.putFDList(op, fds);
+    }
 
-	private void propagateFDsAndEquivClasses(ILogicalOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		ILogicalOperator inp1 = op.getInputs().get(0).getValue();
-		Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
-		ctx.putEquivalenceClassMap(op, eqClasses);
-		List<FunctionalDependency> fds = getOrComputeFDs(inp1, ctx);
-		ctx.putFDList(op, fds);
-	}
+    private Map<LogicalVariable, EquivalenceClass> getOrComputeEqClasses(ILogicalOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        Map<LogicalVariable, EquivalenceClass> eqClasses = ctx.getEquivalenceClassMap(op);
+        if (eqClasses == null) {
+            op.accept(this, ctx);
+            eqClasses = ctx.getEquivalenceClassMap(op);
+        }
+        return eqClasses;
+    }
 
-	private Map<LogicalVariable, EquivalenceClass> getOrComputeEqClasses(ILogicalOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		Map<LogicalVariable, EquivalenceClass> eqClasses = ctx.getEquivalenceClassMap(op);
-		if (eqClasses == null) {
-			op.accept(this, ctx);
-			eqClasses = ctx.getEquivalenceClassMap(op);
-		}
-		return eqClasses;
-	}
+    private List<FunctionalDependency> getOrComputeFDs(ILogicalOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        List<FunctionalDependency> fds = ctx.getFDList(op);
+        if (fds == null) {
+            op.accept(this, ctx);
+            fds = ctx.getFDList(op);
+        }
+        return fds;
+    }
 
-	private List<FunctionalDependency> getOrComputeFDs(ILogicalOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		List<FunctionalDependency> fds = ctx.getFDList(op);
-		if (fds == null) {
-			op.accept(this, ctx);
-			fds = ctx.getFDList(op);
-		}
-		return fds;
-	}
+    private void propagateFDsAndEquivClassesForUsedVars(ILogicalOperator op, IOptimizationContext ctx,
+            List<LogicalVariable> usedVariables) throws AlgebricksException {
+        ILogicalOperator op2 = op.getInputs().get(0).getValue();
+        Map<LogicalVariable, EquivalenceClass> eqClasses = new HashMap<LogicalVariable, EquivalenceClass>();
+        ctx.putEquivalenceClassMap(op, eqClasses);
+        List<FunctionalDependency> fds = new ArrayList<FunctionalDependency>();
+        ctx.putFDList(op, fds);
 
-	private void propagateFDsAndEquivClassesForUsedVars(ILogicalOperator op, IOptimizationContext ctx,
-			List<LogicalVariable> usedVariables) throws AlgebricksException {
-		ILogicalOperator op2 = op.getInputs().get(0).getValue();
-		Map<LogicalVariable, EquivalenceClass> eqClasses = new HashMap<LogicalVariable, EquivalenceClass>();
-		ctx.putEquivalenceClassMap(op, eqClasses);
-		List<FunctionalDependency> fds = new ArrayList<FunctionalDependency>();
-		ctx.putFDList(op, fds);
+        Map<LogicalVariable, EquivalenceClass> chldClasses = getOrComputeEqClasses(op2, ctx);
+        for (LogicalVariable v : usedVariables) {
+            EquivalenceClass ec = eqClasses.get(v);
+            if (ec == null) {
+                EquivalenceClass oc = chldClasses.get(v);
+                if (oc == null) {
+                    continue;
+                }
+                List<LogicalVariable> m = new LinkedList<LogicalVariable>();
+                for (LogicalVariable v2 : oc.getMembers()) {
+                    if (usedVariables.contains(v2)) {
+                        m.add(v2);
+                    }
+                }
+                EquivalenceClass nc;
+                if (oc.representativeIsConst()) {
+                    nc = new EquivalenceClass(m, oc.getConstRepresentative());
+                } else if (m.contains(oc.getVariableRepresentative())) {
+                    nc = new EquivalenceClass(m, oc.getVariableRepresentative());
+                } else {
+                    nc = new EquivalenceClass(m, v);
+                }
+                for (LogicalVariable v3 : m) {
+                    eqClasses.put(v3, nc);
+                }
+            }
+        }
 
-		Map<LogicalVariable, EquivalenceClass> chldClasses = getOrComputeEqClasses(op2, ctx);
-		for (LogicalVariable v : usedVariables) {
-			EquivalenceClass ec = eqClasses.get(v);
-			if (ec == null) {
-				EquivalenceClass oc = chldClasses.get(v);
-				if (oc == null) {
-					continue;
-				}
-				List<LogicalVariable> m = new LinkedList<LogicalVariable>();
-				for (LogicalVariable v2 : oc.getMembers()) {
-					if (usedVariables.contains(v2)) {
-						m.add(v2);
-					}
-				}
-				EquivalenceClass nc;
-				if (oc.representativeIsConst()) {
-					nc = new EquivalenceClass(m, oc.getConstRepresentative());
-				} else if (m.contains(oc.getVariableRepresentative())) {
-					nc = new EquivalenceClass(m, oc.getVariableRepresentative());
-				} else {
-					nc = new EquivalenceClass(m, v);
-				}
-				for (LogicalVariable v3 : m) {
-					eqClasses.put(v3, nc);
-				}
-			}
-		}
+        List<FunctionalDependency> chldFds = getOrComputeFDs(op2, ctx);
+        for (FunctionalDependency fd : chldFds) {
+            if (!usedVariables.containsAll(fd.getHead())) {
+                continue;
+            }
+            List<LogicalVariable> tl = new LinkedList<LogicalVariable>();
+            for (LogicalVariable v : fd.getTail()) {
+                if (usedVariables.contains(v)) {
+                    tl.add(v);
+                }
+            }
+            if (!tl.isEmpty()) {
+                FunctionalDependency newFd = new FunctionalDependency(fd.getHead(), tl);
+                fds.add(newFd);
+            }
+        }
+    }
 
-		List<FunctionalDependency> chldFds = getOrComputeFDs(op2, ctx);
-		for (FunctionalDependency fd : chldFds) {
-			if (!usedVariables.containsAll(fd.getHead())) {
-				continue;
-			}
-			List<LogicalVariable> tl = new LinkedList<LogicalVariable>();
-			for (LogicalVariable v : fd.getTail()) {
-				if (usedVariables.contains(v)) {
-					tl.add(v);
-				}
-			}
-			if (!tl.isEmpty()) {
-				FunctionalDependency newFd = new FunctionalDependency(fd.getHead(), tl);
-				fds.add(newFd);
-			}
-		}
-	}
+    private void fdsEqClassesForAbstractUnnestOperator(AbstractUnnestOperator op, IOptimizationContext ctx)
+            throws AlgebricksException {
+        ILogicalOperator inp1 = op.getInputs().get(0).getValue();
+        Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
+        ctx.putEquivalenceClassMap(op, eqClasses);
+        List<FunctionalDependency> fds = getOrComputeFDs(inp1, ctx);
+        ctx.putFDList(op, fds);
 
-	private void fdsEqClassesForAbstractUnnestOperator(AbstractUnnestOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		ILogicalOperator inp1 = op.getInputs().get(0).getValue();
-		Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
-		ctx.putEquivalenceClassMap(op, eqClasses);
-		List<FunctionalDependency> fds = getOrComputeFDs(inp1, ctx);
-		ctx.putFDList(op, fds);
+        ILogicalExpression expr = op.getExpressionRef().getValue();
+        if (expr.getExpressionTag() == LogicalExpressionTag.FUNCTION_CALL) {
+            AbstractFunctionCallExpression afe = (AbstractFunctionCallExpression) expr;
+            if (afe.getKind() == FunctionKind.UNNEST && ((UnnestingFunctionCallExpression) afe).returnsUniqueValues()) {
+                List<LogicalVariable> vars = new ArrayList<LogicalVariable>();
+                VariableUtilities.getLiveVariables(op, vars);
+                ArrayList<LogicalVariable> h = new ArrayList<LogicalVariable>();
+                h.addAll(op.getVariables());
+                FunctionalDependency fd = new FunctionalDependency(h, vars);
+                fds.add(fd);
+            }
+        }
+    }
 
-		ILogicalExpression expr = op.getExpressionRef().getValue();
-		if (expr.getExpressionTag() == LogicalExpressionTag.FUNCTION_CALL) {
-			AbstractFunctionCallExpression afe = (AbstractFunctionCallExpression) expr;
-			if (afe.getKind() == FunctionKind.UNNEST && ((UnnestingFunctionCallExpression) afe).returnsUniqueValues()) {
-				List<LogicalVariable> vars = new ArrayList<LogicalVariable>();
-				VariableUtilities.getLiveVariables(op, vars);
-				ArrayList<LogicalVariable> h = new ArrayList<LogicalVariable>();
-				h.addAll(op.getVariables());
-				FunctionalDependency fd = new FunctionalDependency(h, vars);
-				fds.add(fd);
-			}
-		}
-	}
+    public static void setEmptyFDsEqClasses(ILogicalOperator op, IOptimizationContext ctx) {
+        Map<LogicalVariable, EquivalenceClass> eqClasses = new HashMap<LogicalVariable, EquivalenceClass>();
+        ctx.putEquivalenceClassMap(op, eqClasses);
+        List<FunctionalDependency> fds = new ArrayList<FunctionalDependency>();
+        ctx.putFDList(op, fds);
+    }
 
-	private void fdsEqClassesForExternalAccessOperator(ExternalDataAccessByRIDOperator op, IOptimizationContext ctx)
-			throws AlgebricksException {
-		ILogicalOperator inp1 = op.getInputs().get(0).getValue();
-		Map<LogicalVariable, EquivalenceClass> eqClasses = getOrComputeEqClasses(inp1, ctx);
-		ctx.putEquivalenceClassMap(op, eqClasses);
-		List<FunctionalDependency> fds = getOrComputeFDs(inp1, ctx);
-		ctx.putFDList(op, fds);
-		List<LogicalVariable> vars = new ArrayList<LogicalVariable>();
-		VariableUtilities.getLiveVariables(op, vars);
-		ArrayList<LogicalVariable> h = new ArrayList<LogicalVariable>();
-		h.addAll(op.getVariables());
-		FunctionalDependency fd = new FunctionalDependency(h, vars);
-		fds.add(fd);
-	}
+    private LogicalVariable getNewGbyVar(GroupByOperator g, LogicalVariable v) {
+        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : g.getGroupByList()) {
+            ILogicalExpression e = p.second.getValue();
+            if (e.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
+                LogicalVariable v2 = ((VariableReferenceExpression) e).getVariableReference();
+                if (v2 == v) {
+                    return p.first;
+                }
+            }
+        }
+        return null;
+    }
 
-	public static void setEmptyFDsEqClasses(ILogicalOperator op, IOptimizationContext ctx) {
-		Map<LogicalVariable, EquivalenceClass> eqClasses = new HashMap<LogicalVariable, EquivalenceClass>();
-		ctx.putEquivalenceClassMap(op, eqClasses);
-		List<FunctionalDependency> fds = new ArrayList<FunctionalDependency>();
-		ctx.putFDList(op, fds);
-	}
+    private LogicalVariable getNewDecorVar(GroupByOperator g, LogicalVariable v) {
+        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : g.getDecorList()) {
+            ILogicalExpression e = p.second.getValue();
+            if (e.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
+                LogicalVariable v2 = ((VariableReferenceExpression) e).getVariableReference();
+                if (v2 == v) {
+                    return (p.first != null) ? p.first : v2;
+                }
+            }
+        }
+        return null;
+    }
 
-	private LogicalVariable getNewGbyVar(GroupByOperator g, LogicalVariable v) {
-		for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : g.getGroupByList()) {
-			ILogicalExpression e = p.second.getValue();
-			if (e.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
-				LogicalVariable v2 = ((VariableReferenceExpression) e).getVariableReference();
-				if (v2 == v) {
-					return p.first;
-				}
-			}
-		}
-		return null;
-	}
-
-	private LogicalVariable getNewDecorVar(GroupByOperator g, LogicalVariable v) {
-		for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : g.getDecorList()) {
-			ILogicalExpression e = p.second.getValue();
-			if (e.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
-				LogicalVariable v2 = ((VariableReferenceExpression) e).getVariableReference();
-				if (v2 == v) {
-					return (p.first != null) ? p.first : v2;
-				}
-			}
-		}
-		return null;
-	}
-
-	@Override
-	public Void visitExtensionOperator(ExtensionOperator op, IOptimizationContext ctx) throws AlgebricksException {
-		propagateFDsAndEquivClasses(op, ctx);
-		return null;
-	}
+    @Override
+    public Void visitExtensionOperator(ExtensionOperator op, IOptimizationContext ctx) throws AlgebricksException {
+        propagateFDsAndEquivClasses(op, ctx);
+        return null;
+    }
 
 }
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java
index 0561091..97d257a 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismOperatorVisitor.java
@@ -41,7 +41,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -343,14 +342,6 @@
         isomorphic = op.getExpressionRef().getValue().equals(unnestOpArg.getExpressionRef().getValue());
         return isomorphic;
     }
-    
-    //not sure if this is correct!
-    @Override
-	public Boolean visitExternalDataAccessByRIDOperator(
-			ExternalDataAccessByRIDOperator op, ILogicalOperator arg)
-			throws AlgebricksException {
-    	return Boolean.FALSE;
-	}
 
     @Override
     public Boolean visitDataScanOperator(DataSourceScanOperator op, ILogicalOperator arg) throws AlgebricksException {
@@ -739,16 +730,6 @@
             return new UnnestMapOperator(newInputList, deepCopyExpressionRef(op.getExpressionRef()),
                     new ArrayList<Object>(op.getVariableTypes()), op.propagatesInput());
         }
-        
-        @Override
-		public ILogicalOperator visitExternalDataAccessByRIDOperator(
-				ExternalDataAccessByRIDOperator op, Void arg)
-        {
-        ArrayList<LogicalVariable> newInputList = new ArrayList<LogicalVariable>();
-        newInputList.addAll(op.getVariables());
-        return new ExternalDataAccessByRIDOperator(newInputList, deepCopyExpressionRef(op.getExpressionRef()),
-                new ArrayList<Object>(op.getVariableTypes()));
-		}
 
         @Override
         public ILogicalOperator visitDataScanOperator(DataSourceScanOperator op, Void arg) throws AlgebricksException {
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismVariableMappingVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismVariableMappingVisitor.java
index 407f7dc8..eecace7 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismVariableMappingVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/IsomorphismVariableMappingVisitor.java
@@ -40,7 +40,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -199,13 +198,6 @@
         mapVariablesStandard(op, arg);
         return null;
     }
-    
-    @Override
-	public Void visitExternalDataAccessByRIDOperator(
-			ExternalDataAccessByRIDOperator op, ILogicalOperator arg)
-			throws AlgebricksException {
-		return null;
-	}
 
     @Override
     public Void visitDataScanOperator(DataSourceScanOperator op, ILogicalOperator arg) throws AlgebricksException {
@@ -430,5 +422,4 @@
         return null;
     }
 
-
 }
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/LogicalPropertiesVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/LogicalPropertiesVisitor.java
index c978bac..277b5a3 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/LogicalPropertiesVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/LogicalPropertiesVisitor.java
@@ -32,7 +32,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -326,12 +325,4 @@
         return null;
     }
 
-	@Override
-	public Void visitExternalDataAccessByRIDOperator(
-			ExternalDataAccessByRIDOperator op, IOptimizationContext arg)
-			throws AlgebricksException {
-		// TODO Auto-generated method stub
-		return null;
-	}
-
 }
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/ProducedVariableVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/ProducedVariableVisitor.java
index b76078e..8673a77 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/ProducedVariableVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/ProducedVariableVisitor.java
@@ -35,7 +35,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -200,12 +199,6 @@
     public Void visitUnnestMapOperator(UnnestMapOperator op, Void arg) throws AlgebricksException {
         producedVariables.addAll(op.getVariables());
         return null;
-    }
-    
-    @Override
-    public Void visitExternalDataAccessByRIDOperator(ExternalDataAccessByRIDOperator op, Void arg) throws AlgebricksException {
-        producedVariables.add(op.getVariables().get(0));
-        return null;
     }
 
     @Override
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/SchemaVariableVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/SchemaVariableVisitor.java
index 82ea1a7..5606e72 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/SchemaVariableVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/SchemaVariableVisitor.java
@@ -36,7 +36,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -227,13 +226,7 @@
         standardLayout(op);
         return null;
     }
-
-    @Override
-    public Void visitExternalDataAccessByRIDOperator(ExternalDataAccessByRIDOperator op, Void arg) throws AlgebricksException {
-    	VariableUtilities.getProducedVariables(op, schemaVariables);
-        return null;
-    }
-    
+
     @Override
     public Void visitUnnestOperator(UnnestOperator op, Void arg) throws AlgebricksException {
         standardLayout(op);
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/SubstituteVariableVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/SubstituteVariableVisitor.java
index 3964e56..3d6b989 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/SubstituteVariableVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/SubstituteVariableVisitor.java
@@ -36,7 +36,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -300,21 +299,6 @@
         op.getExpressionRef().getValue().substituteVar(pair.first, pair.second);
         substVarTypes(op, pair);
         return null;
-    }
-    
-    @Override
-    public Void visitExternalDataAccessByRIDOperator(ExternalDataAccessByRIDOperator op, Pair<LogicalVariable, LogicalVariable> pair)
-            throws AlgebricksException {
-        List<LogicalVariable> variables = op.getVariables();
-        for (int i = 0; i < variables.size(); i++) {
-            if (variables.get(i) == pair.first) {
-                variables.set(i, pair.second);
-                return null;
-            }
-        }
-        op.getExpressionRef().getValue().substituteVar(pair.first, pair.second);
-        substVarTypes(op, pair);
-        return null;
     }
 
     @Override
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/UsedVariableVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/UsedVariableVisitor.java
index 9b4164a..d05adfb 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/UsedVariableVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/UsedVariableVisitor.java
@@ -35,7 +35,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -280,13 +279,7 @@
         op.getExpressionRef().getValue().getUsedVariables(usedVariables);
         return null;
     }
-
-    @Override
-    public Void visitExternalDataAccessByRIDOperator(ExternalDataAccessByRIDOperator op, Void arg) {
-        op.getExpressionRef().getValue().getUsedVariables(usedVariables);
-        return null;
-    }
-    
+
     @Override
     public Void visitUnnestOperator(UnnestOperator op, Void arg) {
         op.getExpressionRef().getValue().getUsedVariables(usedVariables);
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitor.java
index a20d20d..49ec269 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitor.java
@@ -33,7 +33,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -235,13 +234,6 @@
         addIndent(buffer, indent).append("unnest-map " + op.getVariables() + " <- " + op.getExpressionRef().getValue());
         return buffer.toString();
     }
-    
-    @Override
-    public String visitExternalDataAccessByRIDOperator(ExternalDataAccessByRIDOperator op, Integer indent) throws AlgebricksException {
-    	StringBuilder buffer = new StringBuilder();
-        addIndent(buffer, indent).append("external-access-by-rid " + op.getVariables() + " <- " + op.getExpressionRef().getValue());
-        return buffer.toString();
-    }
 
     @Override
     public String visitDataScanOperator(DataSourceScanOperator op, Integer indent) {
diff --git a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/visitors/ILogicalOperatorVisitor.java b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/visitors/ILogicalOperatorVisitor.java
index ca7d21b..0467d63 100644
--- a/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/visitors/ILogicalOperatorVisitor.java
+++ b/algebricks/algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/visitors/ILogicalOperatorVisitor.java
@@ -23,7 +23,6 @@
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.EmptyTupleSourceOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExtensionOperator;
-import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExternalDataAccessByRIDOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.IndexInsertDeleteOperator;
 import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.InnerJoinOperator;
@@ -89,8 +88,6 @@
     public R visitUnnestOperator(UnnestOperator op, T arg) throws AlgebricksException;
 
     public R visitUnnestMapOperator(UnnestMapOperator op, T arg) throws AlgebricksException;
-    
-    public R visitExternalDataAccessByRIDOperator(ExternalDataAccessByRIDOperator op, T arg) throws AlgebricksException;
 
     public R visitDataScanOperator(DataSourceScanOperator op, T arg) throws AlgebricksException;
 
diff --git a/hyracks/hyracks-control/hyracks-control-nc/src/main/java/edu/uci/ics/hyracks/control/nc/Task.java b/hyracks/hyracks-control/hyracks-control-nc/src/main/java/edu/uci/ics/hyracks/control/nc/Task.java
index 09eeab6..c72ced1 100644
--- a/hyracks/hyracks-control/hyracks-control-nc/src/main/java/edu/uci/ics/hyracks/control/nc/Task.java
+++ b/hyracks/hyracks-control/hyracks-control-nc/src/main/java/edu/uci/ics/hyracks/control/nc/Task.java
@@ -278,6 +278,9 @@
             removePendingThread(ct);
         }
         if (!exceptions.isEmpty()) {
+            for (Exception e : exceptions) {
+                e.printStackTrace();
+            }
             NodeControllerService ncs = joblet.getNodeController();
             ExceptionUtils.setNodeIds(exceptions, ncs.getId());
             ncs.getWorkQueue().schedule(new NotifyTaskFailureWork(ncs, this, exceptions));
diff --git a/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/dataflow/LSMBTreeDataflowHelper.java b/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/dataflow/LSMBTreeDataflowHelper.java
index 35c9bcb..8a3c313 100644
--- a/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/dataflow/LSMBTreeDataflowHelper.java
+++ b/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/dataflow/LSMBTreeDataflowHelper.java
@@ -23,7 +23,7 @@
 import edu.uci.ics.hyracks.storage.am.common.dataflow.AbstractTreeIndexOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.lsm.btree.util.LSMBTreeUtils;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -35,17 +35,17 @@
     public LSMBTreeDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx, int partition,
             List<IVirtualBufferCache> virtualBufferCaches, ILSMMergePolicy mergePolicy,
             ILSMOperationTrackerProvider opTrackerFactory, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationCallbackFactory ioOpCallbackFactory) {
         this(opDesc, ctx, partition, virtualBufferCaches, DEFAULT_BLOOM_FILTER_FALSE_POSITIVE_RATE, mergePolicy,
-                opTrackerFactory, ioScheduler, ioOpCallbackProvider);
+                opTrackerFactory, ioScheduler, ioOpCallbackFactory);
     }
 
     public LSMBTreeDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx, int partition,
-            List<IVirtualBufferCache> virtualBufferCaches, double bloomFilterFalsePositiveRate, ILSMMergePolicy mergePolicy,
-            ILSMOperationTrackerProvider opTrackerFactory, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            List<IVirtualBufferCache> virtualBufferCaches, double bloomFilterFalsePositiveRate,
+            ILSMMergePolicy mergePolicy, ILSMOperationTrackerProvider opTrackerFactory,
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackFactory ioOpCallbackFactory) {
         super(opDesc, ctx, partition, virtualBufferCaches, bloomFilterFalsePositiveRate, mergePolicy, opTrackerFactory,
-                ioScheduler, ioOpCallbackProvider);
+                ioScheduler, ioOpCallbackFactory);
     }
 
     @Override
@@ -55,6 +55,6 @@
                 opDesc.getStorageManager().getFileMapProvider(ctx), treeOpDesc.getTreeIndexTypeTraits(),
                 treeOpDesc.getTreeIndexComparatorFactories(), treeOpDesc.getTreeIndexBloomFilterKeyFields(),
                 bloomFilterFalsePositiveRate, mergePolicy, opTrackerFactory.getOperationTracker(ctx), ioScheduler,
-                ioOpCallbackProvider);
+                ioOpCallbackFactory.createIOOperationCallback());
     }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/dataflow/LSMBTreeDataflowHelperFactory.java b/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/dataflow/LSMBTreeDataflowHelperFactory.java
index f4be88f..104a70d 100644
--- a/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/dataflow/LSMBTreeDataflowHelperFactory.java
+++ b/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/dataflow/LSMBTreeDataflowHelperFactory.java
@@ -18,7 +18,7 @@
 import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicyProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -31,10 +31,10 @@
 
     public LSMBTreeDataflowHelperFactory(IVirtualBufferCacheProvider virtualBufferCacheProvider,
             ILSMMergePolicyProvider mergePolicyProvider, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationSchedulerProvider ioSchedulerProvider, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationSchedulerProvider ioSchedulerProvider, ILSMIOOperationCallbackFactory ioOpCallbackFactory,
             double bloomFilterFalsePositiveRate) {
         super(virtualBufferCacheProvider, mergePolicyProvider, opTrackerFactory, ioSchedulerProvider,
-                ioOpCallbackProvider, bloomFilterFalsePositiveRate);
+                ioOpCallbackFactory, bloomFilterFalsePositiveRate);
     }
 
     @Override
@@ -43,6 +43,6 @@
         return new LSMBTreeDataflowHelper(opDesc, ctx, partition,
                 virtualBufferCacheProvider.getVirtualBufferCaches(ctx), bloomFilterFalsePositiveRate,
                 mergePolicyProvider.getMergePolicy(ctx), opTrackerFactory, ioSchedulerProvider.getIOScheduler(ctx),
-                ioOpCallbackProvider);
+                ioOpCallbackFactory);
     }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/impls/LSMBTree.java b/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/impls/LSMBTree.java
index c8ed0d0..33ae7bb 100644
--- a/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/impls/LSMBTree.java
+++ b/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/impls/LSMBTree.java
@@ -92,9 +92,9 @@
             TreeIndexFactory<BTree> bulkLoadBTreeFactory, BloomFilterFactory bloomFilterFactory,
             double bloomFilterFalsePositiveRate, IFileMapProvider diskFileMapProvider, int fieldCount,
             IBinaryComparatorFactory[] cmpFactories, ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallback ioOpCallback) {
         super(virtualBufferCaches, diskBTreeFactory.getBufferCache(), fileManager, diskFileMapProvider,
-                bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider);
+                bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler, ioOpCallback);
         int i = 0;
         for (IVirtualBufferCache virtualBufferCache : virtualBufferCaches) {
             LSMBTreeMemoryComponent mutableComponent = new LSMBTreeMemoryComponent(new BTree(virtualBufferCache,
@@ -165,7 +165,7 @@
 
         if (flushOnExit) {
             BlockingIOOperationCallbackWrapper cb = new BlockingIOOperationCallbackWrapper(
-                    ioOpCallbackProvider.getIOOperationCallback(this));
+                    ioOpCallback);
             ILSMIndexAccessor accessor = createAccessor(NoOpOperationCallback.INSTANCE, NoOpOperationCallback.INSTANCE);
             accessor.scheduleFlush(cb);
             try {
diff --git a/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeUtils.java b/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeUtils.java
index f43c8a6..8b363ff 100644
--- a/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeUtils.java
+++ b/hyracks/hyracks-storage-am-lsm-btree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeUtils.java
@@ -33,7 +33,7 @@
 import edu.uci.ics.hyracks.storage.am.lsm.btree.impls.LSMBTreeFileManager;
 import edu.uci.ics.hyracks.storage.am.lsm.btree.tuples.LSMBTreeCopyTupleWriterFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.btree.tuples.LSMBTreeTupleWriterFactory;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndexFileManager;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
@@ -49,7 +49,7 @@
             IBufferCache diskBufferCache, IFileMapProvider diskFileMapProvider, ITypeTraits[] typeTraits,
             IBinaryComparatorFactory[] cmpFactories, int[] bloomFilterKeyFields, double bloomFilterFalsePositiveRate,
             ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationCallback ioOpCallback) {
         LSMBTreeTupleWriterFactory insertTupleWriterFactory = new LSMBTreeTupleWriterFactory(typeTraits,
                 cmpFactories.length, false);
         LSMBTreeTupleWriterFactory deleteTupleWriterFactory = new LSMBTreeTupleWriterFactory(typeTraits,
@@ -78,7 +78,7 @@
         LSMBTree lsmTree = new LSMBTree(virtualBufferCaches, interiorFrameFactory, insertLeafFrameFactory,
                 deleteLeafFrameFactory, fileNameManager, diskBTreeFactory, bulkLoadBTreeFactory, bloomFilterFactory,
                 bloomFilterFalsePositiveRate, diskFileMapProvider, typeTraits.length, cmpFactories, mergePolicy,
-                opTracker, ioScheduler, ioOpCallbackProvider);
+                opTracker, ioScheduler, ioOpCallback);
         return lsmTree;
     }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIOOperationCallback.java b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIOOperationCallback.java
index 7086b59..9af08fa 100644
--- a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIOOperationCallback.java
+++ b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIOOperationCallback.java
@@ -17,12 +17,36 @@
 import java.util.List;
 
 import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.LSMOperationType;
 
 public interface ILSMIOOperationCallback {
-    public void beforeOperation() throws HyracksDataException;
 
-    public void afterOperation(List<ILSMComponent> oldComponents, ILSMComponent newComponent)
+    /**
+     * This method is called on an IO operation sometime before the operation is executed.
+     * (i.e. IO operations could be flush or merge operations.)
+     */
+    public void beforeOperation(LSMOperationType opType) throws HyracksDataException;
+
+    /**
+     * This method is called on an IO operation sometime after the operation was completed.
+     * (i.e. IO operations could be flush or merge operations.)
+     * 
+     * @param oldComponents
+     * @param newComponent
+     * @throws HyracksDataException
+     */
+    public void afterOperation(LSMOperationType opType, List<ILSMComponent> oldComponents, ILSMComponent newComponent)
             throws HyracksDataException;
 
-    public void afterFinalize(ILSMComponent newComponent) throws HyracksDataException;
+    /**
+     * This method is called on an IO operation when the operation needs any cleanup works
+     * regardless that the IO operation was executed or not. Once the IO operation is executed,
+     * this method should be called after ILSMIOOperationCallback.afterOperation() was called.
+     * 
+     * @param newComponent
+     * @throws HyracksDataException
+     */
+    public void afterFinalize(LSMOperationType opType, ILSMComponent newComponent) throws HyracksDataException;
+
+    public void setNumOfMutableComponents(int count);
 }
diff --git a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIOOperationCallbackFactory.java b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIOOperationCallbackFactory.java
index 6dbce32..804142e 100644
--- a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIOOperationCallbackFactory.java
+++ b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIOOperationCallbackFactory.java
@@ -17,5 +17,5 @@
 import java.io.Serializable;
 
 public interface ILSMIOOperationCallbackFactory extends Serializable {
-    public ILSMIOOperationCallback createIOOperationCallback(Object syncObj);
+    public ILSMIOOperationCallback createIOOperationCallback();
 }
diff --git a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIndex.java b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIndex.java
index 416a15b..d37a105 100644
--- a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIndex.java
+++ b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMIndex.java
@@ -41,6 +41,8 @@
     public ILSMOperationTracker getOperationTracker();
 
     public ILSMIOOperationScheduler getIOScheduler();
+    
+    public ILSMIOOperationCallback getIOOperationCallback();
 
     public List<ILSMComponent> getImmutableComponents();
 }
diff --git a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/dataflow/AbstractLSMIndexDataflowHelper.java b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/dataflow/AbstractLSMIndexDataflowHelper.java
index b1bf6b4..e277edc 100644
--- a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/dataflow/AbstractLSMIndexDataflowHelper.java
+++ b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/dataflow/AbstractLSMIndexDataflowHelper.java
@@ -20,7 +20,7 @@
 import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -36,26 +36,26 @@
     protected final ILSMMergePolicy mergePolicy;
     protected final ILSMIOOperationScheduler ioScheduler;
     protected final ILSMOperationTrackerProvider opTrackerFactory;
-    protected final ILSMIOOperationCallbackProvider ioOpCallbackProvider;
+    protected final ILSMIOOperationCallbackFactory ioOpCallbackFactory;
 
     public AbstractLSMIndexDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx, int partition,
             List<IVirtualBufferCache> virtualBufferCaches, ILSMMergePolicy mergePolicy,
             ILSMOperationTrackerProvider opTrackerFactory, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationCallbackFactory ioOpCallbackFactory) {
         this(opDesc, ctx, partition, virtualBufferCaches, DEFAULT_BLOOM_FILTER_FALSE_POSITIVE_RATE, mergePolicy,
-                opTrackerFactory, ioScheduler, ioOpCallbackProvider);
+                opTrackerFactory, ioScheduler, ioOpCallbackFactory);
     }
 
     public AbstractLSMIndexDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx, int partition,
             List<IVirtualBufferCache> virtualBufferCaches, double bloomFilterFalsePositiveRate,
             ILSMMergePolicy mergePolicy, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackFactory ioOpCallbackFactory) {
         super(opDesc, ctx, partition);
         this.virtualBufferCaches = virtualBufferCaches;
         this.bloomFilterFalsePositiveRate = bloomFilterFalsePositiveRate;
         this.mergePolicy = mergePolicy;
         this.opTrackerFactory = opTrackerFactory;
         this.ioScheduler = ioScheduler;
-        this.ioOpCallbackProvider = ioOpCallbackProvider;
+        this.ioOpCallbackFactory = ioOpCallbackFactory;
     }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/dataflow/AbstractLSMIndexDataflowHelperFactory.java b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/dataflow/AbstractLSMIndexDataflowHelperFactory.java
index 205bf27..2c082bb 100644
--- a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/dataflow/AbstractLSMIndexDataflowHelperFactory.java
+++ b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/dataflow/AbstractLSMIndexDataflowHelperFactory.java
@@ -16,7 +16,7 @@
 package edu.uci.ics.hyracks.storage.am.lsm.common.dataflow;
 
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexDataflowHelperFactory;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicyProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -29,18 +29,18 @@
     protected final ILSMMergePolicyProvider mergePolicyProvider;
     protected final ILSMOperationTrackerProvider opTrackerFactory;
     protected final ILSMIOOperationSchedulerProvider ioSchedulerProvider;
-    protected final ILSMIOOperationCallbackProvider ioOpCallbackProvider;
+    protected final ILSMIOOperationCallbackFactory ioOpCallbackFactory;
     protected final double bloomFilterFalsePositiveRate;
 
     public AbstractLSMIndexDataflowHelperFactory(IVirtualBufferCacheProvider virtualBufferCacheProvider,
             ILSMMergePolicyProvider mergePolicyProvider, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationSchedulerProvider ioSchedulerProvider, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationSchedulerProvider ioSchedulerProvider, ILSMIOOperationCallbackFactory ioOpCallbackFactory,
             double bloomFilterFalsePositiveRate) {
         this.virtualBufferCacheProvider = virtualBufferCacheProvider;
         this.mergePolicyProvider = mergePolicyProvider;
         this.opTrackerFactory = opTrackerFactory;
         this.ioSchedulerProvider = ioSchedulerProvider;
-        this.ioOpCallbackProvider = ioOpCallbackProvider;
+        this.ioOpCallbackFactory = ioOpCallbackFactory;
         this.bloomFilterFalsePositiveRate = bloomFilterFalsePositiveRate;
     }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/AbstractLSMIndex.java b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/AbstractLSMIndex.java
index 794f440..44bcfc2 100644
--- a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/AbstractLSMIndex.java
+++ b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/AbstractLSMIndex.java
@@ -26,6 +26,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndexMetaDataFrame;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMComponent;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMHarness;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndexFileManager;
@@ -42,7 +43,7 @@
     protected final ILSMHarness lsmHarness;
 
     protected final ILSMIOOperationScheduler ioScheduler;
-    protected final ILSMIOOperationCallbackProvider ioOpCallbackProvider;
+    protected final ILSMIOOperationCallback ioOpCallback;
 
     // In-memory components.   
     protected final List<ILSMComponent> memoryComponents;
@@ -63,14 +64,15 @@
     public AbstractLSMIndex(List<IVirtualBufferCache> virtualBufferCaches, IBufferCache diskBufferCache,
             ILSMIndexFileManager fileManager, IFileMapProvider diskFileMapProvider,
             double bloomFilterFalsePositiveRate, ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallback ioOpCallback) {
         this.virtualBufferCaches = virtualBufferCaches;
         this.diskBufferCache = diskBufferCache;
         this.diskFileMapProvider = diskFileMapProvider;
         this.fileManager = fileManager;
         this.bloomFilterFalsePositiveRate = bloomFilterFalsePositiveRate;
         this.ioScheduler = ioScheduler;
-        this.ioOpCallbackProvider = ioOpCallbackProvider;
+        this.ioOpCallback = ioOpCallback;
+        this.ioOpCallback.setNumOfMutableComponents(virtualBufferCaches.size());
         lsmHarness = new LSMHarness(this, mergePolicy, opTracker);
         isActivated = false;
         diskComponents = new LinkedList<ILSMComponent>();
@@ -179,6 +181,11 @@
     }
 
     @Override
+    public ILSMIOOperationCallback getIOOperationCallback() {
+        return ioOpCallback;
+    }
+
+    @Override
     public IBufferCache getBufferCache() {
         return diskBufferCache;
     }
diff --git a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/BlockingIOOperationCallbackWrapper.java b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/BlockingIOOperationCallbackWrapper.java
index a7ca95f..fefe812 100644
--- a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/BlockingIOOperationCallbackWrapper.java
+++ b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/BlockingIOOperationCallbackWrapper.java
@@ -38,20 +38,25 @@
     }
 
     @Override
-    public void beforeOperation() throws HyracksDataException {
-        wrappedCallback.beforeOperation();
+    public void beforeOperation(LSMOperationType opType) throws HyracksDataException {
+        wrappedCallback.beforeOperation(opType);
     }
 
     @Override
-    public void afterOperation(List<ILSMComponent> oldComponents, ILSMComponent newComponent)
+    public void afterOperation(LSMOperationType opType, List<ILSMComponent> oldComponents, ILSMComponent newComponent)
             throws HyracksDataException {
-        wrappedCallback.afterOperation(oldComponents, newComponent);
+        wrappedCallback.afterOperation(opType, oldComponents, newComponent);
     }
 
     @Override
-    public synchronized void afterFinalize(ILSMComponent newComponent) throws HyracksDataException {
-        wrappedCallback.afterFinalize(newComponent);
+    public synchronized void afterFinalize(LSMOperationType opType, ILSMComponent newComponent) throws HyracksDataException {
+        wrappedCallback.afterFinalize(opType, newComponent);
         notifyAll();
         notified = true;
     }
+
+    @Override
+    public void setNumOfMutableComponents(int count) {
+        wrappedCallback.setNumOfMutableComponents(count);
+    }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMHarness.java b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMHarness.java
index 145bfe9..ca775b7 100644
--- a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMHarness.java
+++ b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMHarness.java
@@ -118,6 +118,7 @@
         // Check if there is any action that is needed to be taken based on the operation type
         switch (opType) {
             case FLUSH:
+                lsmIndex.getIOOperationCallback().beforeOperation(LSMOperationType.FLUSH);
                 // Changing the flush status should *always* precede changing the mutable component.
                 lsmIndex.changeFlushStatusForCurrentMutableCompoent(false);
                 lsmIndex.changeMutableComponent();
@@ -125,6 +126,8 @@
                 // again if they can grab and enter the mutable component.
                 opTracker.notifyAll();
                 break;
+            case MERGE:
+                lsmIndex.getIOOperationCallback().beforeOperation(LSMOperationType.MERGE);
             default:
                 break;
         }
@@ -254,9 +257,7 @@
     public void scheduleFlush(ILSMIndexOperationContext ctx, ILSMIOOperationCallback callback)
             throws HyracksDataException {
         if (!getAndEnterComponents(ctx, LSMOperationType.FLUSH, true)) {
-            callback.beforeOperation();
-            callback.afterOperation(null, null);
-            callback.afterFinalize(null);
+            callback.afterFinalize(LSMOperationType.FLUSH, null);
             return;
         }
         lsmIndex.scheduleFlush(ctx, callback);
@@ -271,13 +272,12 @@
 
         ILSMComponent newComponent = null;
         try {
-            operation.getCallback().beforeOperation();
             newComponent = lsmIndex.flush(operation);
-            operation.getCallback().afterOperation(null, newComponent);
+            operation.getCallback().afterOperation(LSMOperationType.FLUSH, null, newComponent);
             lsmIndex.markAsValid(newComponent);
         } finally {
             exitComponents(ctx, LSMOperationType.FLUSH, newComponent, false);
-            operation.getCallback().afterFinalize(newComponent);
+            operation.getCallback().afterFinalize(LSMOperationType.FLUSH, newComponent);
         }
         if (LOGGER.isLoggable(Level.INFO)) {
             LOGGER.info("Finished the flush operation for index: " + lsmIndex);
@@ -289,9 +289,7 @@
             throws HyracksDataException, IndexException {
         // Merge should always be a try operation, because it should never fail to enter the components unless the merge policy is erroneous.
         if (!getAndEnterComponents(ctx, LSMOperationType.MERGE, true)) {
-            callback.beforeOperation();
-            callback.afterOperation(null, null);
-            callback.afterFinalize(null);
+            callback.afterFinalize(LSMOperationType.MERGE, null);
             return;
         }
         lsmIndex.scheduleMerge(ctx, callback);
@@ -306,13 +304,12 @@
 
         ILSMComponent newComponent = null;
         try {
-            operation.getCallback().beforeOperation();
             newComponent = lsmIndex.merge(operation);
-            operation.getCallback().afterOperation(ctx.getComponentHolder(), newComponent);
+            operation.getCallback().afterOperation(LSMOperationType.MERGE, ctx.getComponentHolder(), newComponent);
             lsmIndex.markAsValid(newComponent);
         } finally {
             exitComponents(ctx, LSMOperationType.MERGE, newComponent, false);
-            operation.getCallback().afterFinalize(newComponent);
+            operation.getCallback().afterFinalize(LSMOperationType.MERGE, newComponent);
         }
         if (LOGGER.isLoggable(Level.INFO)) {
             LOGGER.info("Finished the merge operation for index: " + lsmIndex);
diff --git a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/NoOpIOOperationCallback.java b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/NoOpIOOperationCallback.java
index a43b44b..2c8369e 100644
--- a/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/NoOpIOOperationCallback.java
+++ b/hyracks/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/NoOpIOOperationCallback.java
@@ -19,25 +19,26 @@
 import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMComponent;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndex;
 
-public enum NoOpIOOperationCallback implements ILSMIOOperationCallback, ILSMIOOperationCallbackProvider {
+public enum NoOpIOOperationCallback implements ILSMIOOperationCallback, ILSMIOOperationCallbackProvider, ILSMIOOperationCallbackFactory {
     INSTANCE;
 
     @Override
-    public void beforeOperation() throws HyracksDataException {
+    public void beforeOperation(LSMOperationType opType) throws HyracksDataException {
         // Do nothing.
     }
 
     @Override
-    public void afterOperation(List<ILSMComponent> oldComponents, ILSMComponent newComponent)
+    public void afterOperation(LSMOperationType opType, List<ILSMComponent> oldComponents, ILSMComponent newComponent)
             throws HyracksDataException {
         // Do nothing.
     }
 
     @Override
-    public void afterFinalize(ILSMComponent newComponent) throws HyracksDataException {
+    public void afterFinalize(LSMOperationType opType, ILSMComponent newComponent) throws HyracksDataException {
         // Do nothing.
     }
 
@@ -45,4 +46,14 @@
     public ILSMIOOperationCallback getIOOperationCallback(ILSMIndex index) {
         return INSTANCE;
     }
+
+    @Override
+    public ILSMIOOperationCallback createIOOperationCallback() {
+        return INSTANCE;
+    }
+
+    @Override
+    public void setNumOfMutableComponents(int count) {
+        // Do nothing.
+    }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/LSMInvertedIndexDataflowHelper.java b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/LSMInvertedIndexDataflowHelper.java
index ee8febe..ed2f8cf 100644
--- a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/LSMInvertedIndexDataflowHelper.java
+++ b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/LSMInvertedIndexDataflowHelper.java
@@ -21,7 +21,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IIndex;
 import edu.uci.ics.hyracks.storage.am.common.api.IndexException;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -38,17 +38,17 @@
     public LSMInvertedIndexDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx, int partition,
             List<IVirtualBufferCache> virtualBufferCaches, ILSMMergePolicy mergePolicy,
             ILSMOperationTrackerProvider opTrackerFactory, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationCallbackFactory ioOpCallbackFactory) {
         this(opDesc, ctx, partition, virtualBufferCaches, DEFAULT_BLOOM_FILTER_FALSE_POSITIVE_RATE, mergePolicy,
-                opTrackerFactory, ioScheduler, ioOpCallbackProvider);
+                opTrackerFactory, ioScheduler, ioOpCallbackFactory);
     }
 
     public LSMInvertedIndexDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx, int partition,
             List<IVirtualBufferCache> virtualBufferCaches, double bloomFilterFalsePositiveRate,
             ILSMMergePolicy mergePolicy, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackFactory ioOpCallbackFactory) {
         super(opDesc, ctx, partition, virtualBufferCaches, bloomFilterFalsePositiveRate, mergePolicy, opTrackerFactory,
-                ioScheduler, ioOpCallbackProvider);
+                ioScheduler, ioOpCallbackFactory);
     }
 
     @Override
@@ -62,7 +62,8 @@
                     invIndexOpDesc.getInvListsComparatorFactories(), invIndexOpDesc.getTokenTypeTraits(),
                     invIndexOpDesc.getTokenComparatorFactories(), invIndexOpDesc.getTokenizerFactory(),
                     diskBufferCache, file.getFile().getPath(), bloomFilterFalsePositiveRate, mergePolicy,
-                    opTrackerFactory.getOperationTracker(ctx), ioScheduler, ioOpCallbackProvider);
+                    opTrackerFactory.getOperationTracker(ctx), ioScheduler,
+                    ioOpCallbackFactory.createIOOperationCallback());
             return invIndex;
         } catch (IndexException e) {
             throw new HyracksDataException(e);
diff --git a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/LSMInvertedIndexDataflowHelperFactory.java b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/LSMInvertedIndexDataflowHelperFactory.java
index 85aa312..84c7150 100644
--- a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/LSMInvertedIndexDataflowHelperFactory.java
+++ b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/LSMInvertedIndexDataflowHelperFactory.java
@@ -18,7 +18,7 @@
 import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicyProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -31,10 +31,10 @@
 
     public LSMInvertedIndexDataflowHelperFactory(IVirtualBufferCacheProvider virtualBufferCacheProvider,
             ILSMMergePolicyProvider mergePolicyProvider, ILSMOperationTrackerProvider opTrackerProvider,
-            ILSMIOOperationSchedulerProvider ioSchedulerProvider, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationSchedulerProvider ioSchedulerProvider, ILSMIOOperationCallbackFactory ioOpCallbackFactory,
             double bloomFilterFalsePositiveRate) {
         super(virtualBufferCacheProvider, mergePolicyProvider, opTrackerProvider, ioSchedulerProvider,
-                ioOpCallbackProvider, bloomFilterFalsePositiveRate);
+                ioOpCallbackFactory, bloomFilterFalsePositiveRate);
     }
 
     @Override
@@ -43,7 +43,7 @@
         return new LSMInvertedIndexDataflowHelper(opDesc, ctx, partition,
                 virtualBufferCacheProvider.getVirtualBufferCaches(ctx), bloomFilterFalsePositiveRate,
                 mergePolicyProvider.getMergePolicy(ctx), opTrackerFactory, ioSchedulerProvider.getIOScheduler(ctx),
-                ioOpCallbackProvider);
+                ioOpCallbackFactory);
     }
 
 }
diff --git a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/PartitionedLSMInvertedIndexDataflowHelper.java b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/PartitionedLSMInvertedIndexDataflowHelper.java
index 1acb437..57a41ca 100644
--- a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/PartitionedLSMInvertedIndexDataflowHelper.java
+++ b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/PartitionedLSMInvertedIndexDataflowHelper.java
@@ -21,7 +21,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IIndex;
 import edu.uci.ics.hyracks.storage.am.common.api.IndexException;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -38,17 +38,17 @@
     public PartitionedLSMInvertedIndexDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx,
             int partition, List<IVirtualBufferCache> virtualBufferCache, ILSMMergePolicy mergePolicy,
             ILSMOperationTrackerProvider opTrackerFactory, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationCallbackFactory ioOpCallbackFactory) {
         this(opDesc, ctx, partition, virtualBufferCache, DEFAULT_BLOOM_FILTER_FALSE_POSITIVE_RATE, mergePolicy,
-                opTrackerFactory, ioScheduler, ioOpCallbackProvider);
+                opTrackerFactory, ioScheduler, ioOpCallbackFactory);
     }
 
     public PartitionedLSMInvertedIndexDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx,
             int partition, List<IVirtualBufferCache> virtualBufferCaches, double bloomFilterFalsePositiveRate,
             ILSMMergePolicy mergePolicy, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackFactory ioOpCallbackFactory) {
         super(opDesc, ctx, partition, virtualBufferCaches, bloomFilterFalsePositiveRate, mergePolicy, opTrackerFactory,
-                ioScheduler, ioOpCallbackProvider);
+                ioScheduler, ioOpCallbackFactory);
     }
 
     @Override
@@ -62,7 +62,8 @@
                     invIndexOpDesc.getInvListsComparatorFactories(), invIndexOpDesc.getTokenTypeTraits(),
                     invIndexOpDesc.getTokenComparatorFactories(), invIndexOpDesc.getTokenizerFactory(),
                     diskBufferCache, file.getFile().getPath(), bloomFilterFalsePositiveRate, mergePolicy,
-                    opTrackerFactory.getOperationTracker(ctx), ioScheduler, ioOpCallbackProvider);
+                    opTrackerFactory.getOperationTracker(ctx), ioScheduler,
+                    ioOpCallbackFactory.createIOOperationCallback());
             return invIndex;
         } catch (IndexException e) {
             throw new HyracksDataException(e);
diff --git a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/PartitionedLSMInvertedIndexDataflowHelperFactory.java b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/PartitionedLSMInvertedIndexDataflowHelperFactory.java
index 63d99aa..d78ae7e 100644
--- a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/PartitionedLSMInvertedIndexDataflowHelperFactory.java
+++ b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/dataflow/PartitionedLSMInvertedIndexDataflowHelperFactory.java
@@ -18,7 +18,7 @@
 import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicyProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -31,10 +31,10 @@
 
     public PartitionedLSMInvertedIndexDataflowHelperFactory(IVirtualBufferCacheProvider virtualBufferCacheProvider,
             ILSMMergePolicyProvider mergePolicyProvider, ILSMOperationTrackerProvider opTrackerProvider,
-            ILSMIOOperationSchedulerProvider ioSchedulerProvider, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationSchedulerProvider ioSchedulerProvider, ILSMIOOperationCallbackFactory ioOpCallbackFactory,
             double bloomFilterFalsePositiveRate) {
         super(virtualBufferCacheProvider, mergePolicyProvider, opTrackerProvider, ioSchedulerProvider,
-                ioOpCallbackProvider, bloomFilterFalsePositiveRate);
+                ioOpCallbackFactory, bloomFilterFalsePositiveRate);
     }
 
     @Override
@@ -43,6 +43,6 @@
         return new PartitionedLSMInvertedIndexDataflowHelper(opDesc, ctx, partition,
                 virtualBufferCacheProvider.getVirtualBufferCaches(ctx), bloomFilterFalsePositiveRate,
                 mergePolicyProvider.getMergePolicy(ctx), opTrackerFactory, ioSchedulerProvider.getIOScheduler(ctx),
-                ioOpCallbackProvider);
+                ioOpCallbackFactory);
     }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/impls/LSMInvertedIndex.java b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/impls/LSMInvertedIndex.java
index f2f058a..cef6aee 100644
--- a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/impls/LSMInvertedIndex.java
+++ b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/impls/LSMInvertedIndex.java
@@ -52,7 +52,6 @@
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMComponentFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperation;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndexAccessor;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndexAccessorInternal;
@@ -100,9 +99,9 @@
             IBinaryComparatorFactory[] invListCmpFactories, ITypeTraits[] tokenTypeTraits,
             IBinaryComparatorFactory[] tokenCmpFactories, IBinaryTokenizerFactory tokenizerFactory,
             ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) throws IndexException {
+            ILSMIOOperationCallback ioOpCallback) throws IndexException {
         super(virtualBufferCaches, diskInvIndexFactory.getBufferCache(), fileManager, diskFileMapProvider,
-                bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider);
+                bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler, ioOpCallback);
 
         this.tokenizerFactory = tokenizerFactory;
         this.invListTypeTraits = invListTypeTraits;
@@ -211,7 +210,7 @@
         isActivated = false;
         if (flushOnExit) {
             BlockingIOOperationCallbackWrapper cb = new BlockingIOOperationCallbackWrapper(
-                    ioOpCallbackProvider.getIOOperationCallback(this));
+                    ioOpCallback);
             ILSMIndexAccessor accessor = createAccessor(NoOpOperationCallback.INSTANCE, NoOpOperationCallback.INSTANCE);
             accessor.scheduleFlush(cb);
             try {
diff --git a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/impls/PartitionedLSMInvertedIndex.java b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/impls/PartitionedLSMInvertedIndex.java
index 5b0c48d..ddb6060 100644
--- a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/impls/PartitionedLSMInvertedIndex.java
+++ b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/impls/PartitionedLSMInvertedIndex.java
@@ -24,7 +24,7 @@
 import edu.uci.ics.hyracks.storage.am.bloomfilter.impls.BloomFilterFactory;
 import edu.uci.ics.hyracks.storage.am.common.api.IVirtualFreePageManager;
 import edu.uci.ics.hyracks.storage.am.common.api.IndexException;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndexFileManager;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
@@ -46,11 +46,10 @@
             IBinaryComparatorFactory[] invListCmpFactories, ITypeTraits[] tokenTypeTraits,
             IBinaryComparatorFactory[] tokenCmpFactories, IBinaryTokenizerFactory tokenizerFactory,
             ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) throws IndexException {
+            ILSMIOOperationCallback ioOpCallback) throws IndexException {
         super(virtualBufferCaches, diskInvIndexFactory, deletedKeysBTreeFactory, bloomFilterFactory,
                 bloomFilterFalsePositiveRate, fileManager, diskFileMapProvider, invListTypeTraits, invListCmpFactories,
-                tokenTypeTraits, tokenCmpFactories, tokenizerFactory, mergePolicy, opTracker, ioScheduler,
-                ioOpCallbackProvider);
+                tokenTypeTraits, tokenCmpFactories, tokenizerFactory, mergePolicy, opTracker, ioScheduler, ioOpCallback);
     }
 
     @Override
diff --git a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/util/InvertedIndexUtils.java b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/util/InvertedIndexUtils.java
index ed02ba1..372221e 100644
--- a/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/util/InvertedIndexUtils.java
+++ b/hyracks/hyracks-storage-am-lsm-invertedindex/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/util/InvertedIndexUtils.java
@@ -33,7 +33,7 @@
 import edu.uci.ics.hyracks.storage.am.common.frames.LIFOMetaDataFrameFactory;
 import edu.uci.ics.hyracks.storage.am.common.freepage.LinkedListFreePageManagerFactory;
 import edu.uci.ics.hyracks.storage.am.common.tuples.TypeAwareTupleWriterFactory;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -122,7 +122,7 @@
             IBinaryComparatorFactory[] tokenCmpFactories, IBinaryTokenizerFactory tokenizerFactory,
             IBufferCache diskBufferCache, String onDiskDir, double bloomFilterFalsePositiveRate,
             ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) throws IndexException {
+            ILSMIOOperationCallback ioOpCallback) throws IndexException {
 
         BTreeFactory deletedKeysBTreeFactory = createDeletedKeysBTreeFactory(diskFileMapProvider, invListTypeTraits,
                 invListCmpFactories, diskBufferCache);
@@ -147,7 +147,7 @@
         LSMInvertedIndex invIndex = new LSMInvertedIndex(virtualBufferCaches, invIndexFactory, deletedKeysBTreeFactory,
                 bloomFilterFactory, bloomFilterFalsePositiveRate, fileManager, diskFileMapProvider, invListTypeTraits,
                 invListCmpFactories, tokenTypeTraits, tokenCmpFactories, tokenizerFactory, mergePolicy, opTracker,
-                ioScheduler, ioOpCallbackProvider);
+                ioScheduler, ioOpCallback);
         return invIndex;
     }
 
@@ -157,8 +157,7 @@
             ITypeTraits[] tokenTypeTraits, IBinaryComparatorFactory[] tokenCmpFactories,
             IBinaryTokenizerFactory tokenizerFactory, IBufferCache diskBufferCache, String onDiskDir,
             double bloomFilterFalsePositiveRate, ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider)
-            throws IndexException {
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallback ioOpCallback) throws IndexException {
 
         BTreeFactory deletedKeysBTreeFactory = createDeletedKeysBTreeFactory(diskFileMapProvider, invListTypeTraits,
                 invListCmpFactories, diskBufferCache);
@@ -183,7 +182,7 @@
         PartitionedLSMInvertedIndex invIndex = new PartitionedLSMInvertedIndex(virtualBufferCaches, invIndexFactory,
                 deletedKeysBTreeFactory, bloomFilterFactory, bloomFilterFalsePositiveRate, fileManager,
                 diskFileMapProvider, invListTypeTraits, invListCmpFactories, tokenTypeTraits, tokenCmpFactories,
-                tokenizerFactory, mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider);
+                tokenizerFactory, mergePolicy, opTracker, ioScheduler, ioOpCallback);
         return invIndex;
     }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/AbstractLSMRTreeDataflowHelper.java b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/AbstractLSMRTreeDataflowHelper.java
index 5d57aae..636f0cb 100644
--- a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/AbstractLSMRTreeDataflowHelper.java
+++ b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/AbstractLSMRTreeDataflowHelper.java
@@ -27,7 +27,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.AbstractTreeIndexOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -49,11 +49,11 @@
             List<IVirtualBufferCache> virtualBufferCaches, IBinaryComparatorFactory[] btreeComparatorFactories,
             IPrimitiveValueProviderFactory[] valueProviderFactories, RTreePolicyType rtreePolicyType,
             ILSMMergePolicy mergePolicy, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackFactory ioOpCallbackFactory,
             ILinearizeComparatorFactory linearizeCmpFactory) {
         this(opDesc, ctx, partition, virtualBufferCaches, DEFAULT_BLOOM_FILTER_FALSE_POSITIVE_RATE,
                 btreeComparatorFactories, valueProviderFactories, rtreePolicyType, mergePolicy, opTrackerFactory,
-                ioScheduler, ioOpCallbackProvider, linearizeCmpFactory);
+                ioScheduler, ioOpCallbackFactory, linearizeCmpFactory);
     }
 
     public AbstractLSMRTreeDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx, int partition,
@@ -61,10 +61,10 @@
             IBinaryComparatorFactory[] btreeComparatorFactories,
             IPrimitiveValueProviderFactory[] valueProviderFactories, RTreePolicyType rtreePolicyType,
             ILSMMergePolicy mergePolicy, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackFactory ioOpCallbackFactory,
             ILinearizeComparatorFactory linearizeCmpFactory) {
         super(opDesc, ctx, partition, virtualBufferCaches, bloomFilterFalsePositiveRate, mergePolicy, opTrackerFactory,
-                ioScheduler, ioOpCallbackProvider);
+                ioScheduler, ioOpCallbackFactory);
         this.btreeComparatorFactories = btreeComparatorFactories;
         this.valueProviderFactories = valueProviderFactories;
         this.rtreePolicyType = rtreePolicyType;
diff --git a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeDataflowHelper.java b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeDataflowHelper.java
index bc4bca3..92364fa 100644
--- a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeDataflowHelper.java
+++ b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeDataflowHelper.java
@@ -27,7 +27,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
 import edu.uci.ics.hyracks.storage.am.common.api.TreeIndexException;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -44,10 +44,10 @@
             List<IVirtualBufferCache> virtualBufferCaches, IBinaryComparatorFactory[] btreeComparatorFactories,
             IPrimitiveValueProviderFactory[] valueProviderFactories, RTreePolicyType rtreePolicyType,
             ILSMMergePolicy mergePolicy, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackFactory ioOpCallbackFactory,
             ILinearizeComparatorFactory linearizeCmpFactory) {
         super(opDesc, ctx, partition, virtualBufferCaches, btreeComparatorFactories, valueProviderFactories,
-                rtreePolicyType, mergePolicy, opTrackerFactory, ioScheduler, ioOpCallbackProvider, linearizeCmpFactory);
+                rtreePolicyType, mergePolicy, opTrackerFactory, ioScheduler, ioOpCallbackFactory, linearizeCmpFactory);
     }
 
     public LSMRTreeDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx, int partition,
@@ -55,11 +55,11 @@
             IBinaryComparatorFactory[] btreeComparatorFactories,
             IPrimitiveValueProviderFactory[] valueProviderFactories, RTreePolicyType rtreePolicyType,
             ILSMMergePolicy mergePolicy, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackFactory ioOpCallbackFactory,
             ILinearizeComparatorFactory linearizeCmpFactory) {
         super(opDesc, ctx, partition, virtualBufferCaches, bloomFilterFalsePositiveRate, btreeComparatorFactories,
                 valueProviderFactories, rtreePolicyType, mergePolicy, opTrackerFactory, ioScheduler,
-                ioOpCallbackProvider, linearizeCmpFactory);
+                ioOpCallbackFactory, linearizeCmpFactory);
     }
 
     @Override
@@ -72,8 +72,8 @@
         try {
             return LSMRTreeUtils.createLSMTree(virtualBufferCaches, file, diskBufferCache, diskFileMapProvider,
                     typeTraits, rtreeCmpFactories, btreeCmpFactories, valueProviderFactories, rtreePolicyType,
-                    bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider,
-                    linearizeCmpFactory);
+                    bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler,
+                    ioOpCallbackFactory.createIOOperationCallback(), linearizeCmpFactory);
         } catch (TreeIndexException e) {
             throw new HyracksDataException(e);
         }
diff --git a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeDataflowHelperFactory.java b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeDataflowHelperFactory.java
index 99b4219..8254689 100644
--- a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeDataflowHelperFactory.java
+++ b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeDataflowHelperFactory.java
@@ -21,7 +21,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IPrimitiveValueProviderFactory;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicyProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -42,10 +42,10 @@
             RTreePolicyType rtreePolicyType, IBinaryComparatorFactory[] btreeComparatorFactories,
             IVirtualBufferCacheProvider virtualBufferCacheProvider, ILSMMergePolicyProvider mergePolicyProvider,
             ILSMOperationTrackerProvider opTrackerFactory, ILSMIOOperationSchedulerProvider ioSchedulerProvider,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider, ILinearizeComparatorFactory linearizeCmpFactory,
+            ILSMIOOperationCallbackFactory ioOpCallbackFactory, ILinearizeComparatorFactory linearizeCmpFactory,
             double bloomFilterFalsePositiveRate) {
         super(virtualBufferCacheProvider, mergePolicyProvider, opTrackerFactory, ioSchedulerProvider,
-                ioOpCallbackProvider, bloomFilterFalsePositiveRate);
+                ioOpCallbackFactory, bloomFilterFalsePositiveRate);
         this.btreeComparatorFactories = btreeComparatorFactories;
         this.valueProviderFactories = valueProviderFactories;
         this.rtreePolicyType = rtreePolicyType;
@@ -59,6 +59,6 @@
                 virtualBufferCacheProvider.getVirtualBufferCaches(ctx), bloomFilterFalsePositiveRate,
                 btreeComparatorFactories, valueProviderFactories, rtreePolicyType,
                 mergePolicyProvider.getMergePolicy(ctx), opTrackerFactory, ioSchedulerProvider.getIOScheduler(ctx),
-                ioOpCallbackProvider, linearizeCmpFactory);
+                ioOpCallbackFactory, linearizeCmpFactory);
     }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeWithAntiMatterTuplesDataflowHelper.java b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeWithAntiMatterTuplesDataflowHelper.java
index 72f3480..f430456 100644
--- a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeWithAntiMatterTuplesDataflowHelper.java
+++ b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeWithAntiMatterTuplesDataflowHelper.java
@@ -27,7 +27,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
 import edu.uci.ics.hyracks.storage.am.common.api.TreeIndexException;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -40,13 +40,14 @@
 
 public class LSMRTreeWithAntiMatterTuplesDataflowHelper extends AbstractLSMRTreeDataflowHelper {
     public LSMRTreeWithAntiMatterTuplesDataflowHelper(IIndexOperatorDescriptor opDesc, IHyracksTaskContext ctx,
-            int partition, List<IVirtualBufferCache> virtualBufferCaches, IBinaryComparatorFactory[] btreeComparatorFactories,
+            int partition, List<IVirtualBufferCache> virtualBufferCaches,
+            IBinaryComparatorFactory[] btreeComparatorFactories,
             IPrimitiveValueProviderFactory[] valueProviderFactories, RTreePolicyType rtreePolicyType,
             ILSMMergePolicy mergePolicy, ILSMOperationTrackerProvider opTrackerFactory,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackFactory ioOpCallbackFactory,
             ILinearizeComparatorFactory linearizeCmpFactory) {
         super(opDesc, ctx, partition, virtualBufferCaches, btreeComparatorFactories, valueProviderFactories,
-                rtreePolicyType, mergePolicy, opTrackerFactory, ioScheduler, ioOpCallbackProvider, linearizeCmpFactory);
+                rtreePolicyType, mergePolicy, opTrackerFactory, ioScheduler, ioOpCallbackFactory, linearizeCmpFactory);
     }
 
     @Override
@@ -59,7 +60,8 @@
         try {
             return LSMRTreeUtils.createLSMTreeWithAntiMatterTuples(virtualBufferCaches, file, diskBufferCache,
                     diskFileMapProvider, typeTraits, rtreeCmpFactories, btreeCmpFactories, valueProviderFactories,
-                    rtreePolicyType, mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider, linearizeCmpFactory);
+                    rtreePolicyType, mergePolicy, opTracker, ioScheduler,
+                    ioOpCallbackFactory.createIOOperationCallback(), linearizeCmpFactory);
         } catch (TreeIndexException e) {
             throw new HyracksDataException(e);
         }
diff --git a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeWithAntiMatterTuplesDataflowHelperFactory.java b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeWithAntiMatterTuplesDataflowHelperFactory.java
index 00268b3..ef34876 100644
--- a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeWithAntiMatterTuplesDataflowHelperFactory.java
+++ b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/dataflow/LSMRTreeWithAntiMatterTuplesDataflowHelperFactory.java
@@ -22,7 +22,7 @@
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexDataflowHelperFactory;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicyProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerProvider;
@@ -40,14 +40,14 @@
     private final ILSMMergePolicyProvider mergePolicyProvider;
     private final ILSMOperationTrackerProvider opTrackerProvider;
     private final ILSMIOOperationSchedulerProvider ioSchedulerProvider;
-    private final ILSMIOOperationCallbackProvider ioOpCallbackProvider;
+    private final ILSMIOOperationCallbackFactory ioOpCallbackFactory;
     private final ILinearizeComparatorFactory linearizeCmpFactory;
 
     public LSMRTreeWithAntiMatterTuplesDataflowHelperFactory(IPrimitiveValueProviderFactory[] valueProviderFactories,
             RTreePolicyType rtreePolicyType, IBinaryComparatorFactory[] btreeComparatorFactories,
             IVirtualBufferCacheProvider virtualBufferCacheProvider, ILSMMergePolicyProvider mergePolicyProvider,
             ILSMOperationTrackerProvider opTrackerProvider, ILSMIOOperationSchedulerProvider ioSchedulerProvider,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider, ILinearizeComparatorFactory linearizeCmpFactory) {
+            ILSMIOOperationCallbackFactory ioOpCallbackFactory, ILinearizeComparatorFactory linearizeCmpFactory) {
         this.virtualBufferCacheProvider = virtualBufferCacheProvider;
         this.btreeComparatorFactories = btreeComparatorFactories;
         this.valueProviderFactories = valueProviderFactories;
@@ -55,7 +55,7 @@
         this.mergePolicyProvider = mergePolicyProvider;
         this.ioSchedulerProvider = ioSchedulerProvider;
         this.opTrackerProvider = opTrackerProvider;
-        this.ioOpCallbackProvider = ioOpCallbackProvider;
+        this.ioOpCallbackFactory = ioOpCallbackFactory;
         this.linearizeCmpFactory = linearizeCmpFactory;
     }
 
@@ -65,6 +65,6 @@
         return new LSMRTreeWithAntiMatterTuplesDataflowHelper(opDesc, ctx, partition,
                 virtualBufferCacheProvider.getVirtualBufferCaches(ctx), btreeComparatorFactories,
                 valueProviderFactories, rtreePolicyType, mergePolicyProvider.getMergePolicy(ctx), opTrackerProvider,
-                ioSchedulerProvider.getIOScheduler(ctx), ioOpCallbackProvider, linearizeCmpFactory);
+                ioSchedulerProvider.getIOScheduler(ctx), ioOpCallbackFactory, linearizeCmpFactory);
     }
 }
diff --git a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/AbstractLSMRTree.java b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/AbstractLSMRTree.java
index 04118c8..b09e115 100644
--- a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/AbstractLSMRTree.java
+++ b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/AbstractLSMRTree.java
@@ -40,7 +40,7 @@
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.IndexOperation;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMComponent;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMComponentFactory;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndexAccessor;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndexFileManager;
@@ -87,9 +87,9 @@
             IBinaryComparatorFactory[] btreeCmpFactories, ILinearizeComparatorFactory linearizer,
             int[] comparatorFields, IBinaryComparatorFactory[] linearizerArray, double bloomFilterFalsePositiveRate,
             ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationCallback ioOpCallback) {
         super(virtualBufferCaches, componentFactory.getBufferCache(), fileManager, diskFileMapProvider,
-                bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider);
+                bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler, ioOpCallback);
         int i = 0;
         for (IVirtualBufferCache virtualBufferCache : virtualBufferCaches) {
             RTree memRTree = new RTree(virtualBufferCache,
@@ -156,7 +156,7 @@
 
         if (flushOnExit) {
             BlockingIOOperationCallbackWrapper cb = new BlockingIOOperationCallbackWrapper(
-                    ioOpCallbackProvider.getIOOperationCallback(this));
+                    ioOpCallback);
             ILSMIndexAccessor accessor = createAccessor(NoOpOperationCallback.INSTANCE, NoOpOperationCallback.INSTANCE);
             accessor.scheduleFlush(cb);
             try {
diff --git a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTree.java b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTree.java
index 410fde8..a4b6139 100644
--- a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTree.java
+++ b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTree.java
@@ -74,12 +74,12 @@
             IBinaryComparatorFactory[] btreeCmpFactories, ILinearizeComparatorFactory linearizer,
             int[] comparatorFields, IBinaryComparatorFactory[] linearizerArray, ILSMMergePolicy mergePolicy,
             ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationCallback ioOpCallback) {
         super(virtualBufferCaches, rtreeInteriorFrameFactory, rtreeLeafFrameFactory, btreeInteriorFrameFactory,
                 btreeLeafFrameFactory, fileNameManager, new LSMRTreeDiskComponentFactory(diskRTreeFactory,
                         diskBTreeFactory, bloomFilterFactory), diskFileMapProvider, fieldCount, rtreeCmpFactories,
                 btreeCmpFactories, linearizer, comparatorFields, linearizerArray, bloomFilterFalsePositiveRate,
-                mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider);
+                mergePolicy, opTracker, ioScheduler, ioOpCallback);
     }
 
     /**
diff --git a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTreeWithAntiMatterTuples.java b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTreeWithAntiMatterTuples.java
index 0996257..812e942 100644
--- a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTreeWithAntiMatterTuples.java
+++ b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTreeWithAntiMatterTuples.java
@@ -74,11 +74,11 @@
             IBinaryComparatorFactory[] rtreeCmpFactories, IBinaryComparatorFactory[] btreeCmpFactories,
             ILinearizeComparatorFactory linearizer, int[] comparatorFields, IBinaryComparatorFactory[] linearizerArray,
             ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) {
+            ILSMIOOperationCallback ioOpCallback) {
         super(virtualBufferCaches, rtreeInteriorFrameFactory, rtreeLeafFrameFactory, btreeInteriorFrameFactory,
                 btreeLeafFrameFactory, fileManager, new LSMRTreeWithAntiMatterTuplesDiskComponentFactory(diskRTreeFactory),
                 diskFileMapProvider, fieldCount, rtreeCmpFactories, btreeCmpFactories, linearizer, comparatorFields,
-                linearizerArray, 0, mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider);
+                linearizerArray, 0, mergePolicy, opTracker, ioScheduler, ioOpCallback);
         bulkLoaComponentFactory = new LSMRTreeWithAntiMatterTuplesDiskComponentFactory(bulkLoadRTreeFactory);
         this.bTreeTupleSorter = null;
     }
diff --git a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/utils/LSMRTreeUtils.java b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/utils/LSMRTreeUtils.java
index b16d2b6..ee942e7 100644
--- a/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/utils/LSMRTreeUtils.java
+++ b/hyracks/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/utils/LSMRTreeUtils.java
@@ -33,7 +33,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.TreeIndexException;
 import edu.uci.ics.hyracks.storage.am.common.frames.LIFOMetaDataFrameFactory;
 import edu.uci.ics.hyracks.storage.am.common.freepage.LinkedListFreePageManagerFactory;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndexFileManager;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
@@ -65,7 +65,7 @@
             IBinaryComparatorFactory[] rtreeCmpFactories, IBinaryComparatorFactory[] btreeCmpFactories,
             IPrimitiveValueProviderFactory[] valueProviderFactories, RTreePolicyType rtreePolicyType,
             double bloomFilterFalsePositiveRate, ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider,
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallback ioOpCallback,
             ILinearizeComparatorFactory linearizeCmpFactory) throws TreeIndexException {
         LSMTypeAwareTupleWriterFactory rtreeTupleWriterFactory = new LSMTypeAwareTupleWriterFactory(typeTraits, false);
         LSMTypeAwareTupleWriterFactory btreeTupleWriterFactory = new LSMTypeAwareTupleWriterFactory(typeTraits, true);
@@ -105,7 +105,7 @@
                 btreeInteriorFrameFactory, btreeLeafFrameFactory, fileNameManager, diskRTreeFactory, diskBTreeFactory,
                 bloomFilterFactory, bloomFilterFalsePositiveRate, diskFileMapProvider, typeTraits.length,
                 rtreeCmpFactories, btreeCmpFactories, linearizeCmpFactory, comparatorFields, linearizerArray,
-                mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider);
+                mergePolicy, opTracker, ioScheduler, ioOpCallback);
         return lsmTree;
     }
 
@@ -115,7 +115,7 @@
             IBinaryComparatorFactory[] rtreeCmpFactories, IBinaryComparatorFactory[] btreeCmpFactories,
             IPrimitiveValueProviderFactory[] valueProviderFactories, RTreePolicyType rtreePolicyType,
             ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider, ILinearizeComparatorFactory linearizerCmpFactory)
+            ILSMIOOperationCallback ioOpCallback, ILinearizeComparatorFactory linearizerCmpFactory)
             throws TreeIndexException {
         LSMRTreeTupleWriterFactory rtreeTupleWriterFactory = new LSMRTreeTupleWriterFactory(typeTraits, false);
         LSMRTreeTupleWriterFactory btreeTupleWriterFactory = new LSMRTreeTupleWriterFactory(typeTraits, true);
@@ -157,7 +157,7 @@
                 rtreeInteriorFrameFactory, rtreeLeafFrameFactory, btreeInteriorFrameFactory, btreeLeafFrameFactory,
                 fileNameManager, diskRTreeFactory, bulkLoadRTreeFactory, diskFileMapProvider, typeTraits.length,
                 rtreeCmpFactories, btreeCmpFactories, linearizerCmpFactory, comparatorFields, linearizerArray,
-                mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider);
+                mergePolicy, opTracker, ioScheduler, ioOpCallback);
         return lsmTree;
     }
 
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeBulkLoadTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeBulkLoadTest.java
index 753be5d..447c507 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeBulkLoadTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeBulkLoadTest.java
@@ -54,7 +54,7 @@
         return LSMBTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, numKeys,
                 harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(), harness.getOperationTracker(),
-                harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeDeleteTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeDeleteTest.java
index 646343a..0303dbd 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeDeleteTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeDeleteTest.java
@@ -54,7 +54,7 @@
         return LSMBTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, numKeys,
                 harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(), harness.getOperationTracker(),
-                harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeExamplesTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeExamplesTest.java
index b0617a1..dc55f5d 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeExamplesTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeExamplesTest.java
@@ -37,7 +37,7 @@
         return LSMBTreeUtils.createLSMTree(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), typeTraits, cmpFactories,
                 bloomFilterKeyFields, harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Before
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeInsertTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeInsertTest.java
index bce69a2..4fc3960 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeInsertTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeInsertTest.java
@@ -54,7 +54,7 @@
         return LSMBTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, numKeys,
                 harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(), harness.getOperationTracker(),
-                harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeLifecycleTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeLifecycleTest.java
index 0f903e5..f553b72 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeLifecycleTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeLifecycleTest.java
@@ -56,7 +56,7 @@
         testCtx = LSMBTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, fieldSerdes.length,
                 harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(), harness.getOperationTracker(),
-                harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getIOScheduler(), harness.getIOOperationCallback());
         index = testCtx.getIndex();
     }
 
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeMergeTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeMergeTest.java
index ab46f3f..f5cfb32 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeMergeTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeMergeTest.java
@@ -53,7 +53,7 @@
         return LSMBTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, numKeys,
                 harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(), harness.getOperationTracker(),
-                harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeModificationOperationCallbackTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeModificationOperationCallbackTest.java
index cc3389f..2234075 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeModificationOperationCallbackTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeModificationOperationCallbackTest.java
@@ -48,7 +48,7 @@
                 SerdeUtils.serdesToComparatorFactories(keySerdes, keySerdes.length), bloomFilterKeyFields,
                 harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
                 NoOpOperationTrackerProvider.INSTANCE.getOperationTracker(null), harness.getIOScheduler(),
-                harness.getIOOperationCallbackProvider());
+                harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeMultiBulkLoadTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeMultiBulkLoadTest.java
index d7d29a8..277df6b 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeMultiBulkLoadTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeMultiBulkLoadTest.java
@@ -55,7 +55,7 @@
         return LSMBTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, numKeys,
                 harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(), harness.getOperationTracker(),
-                harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeSearchOperationCallbackTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeSearchOperationCallbackTest.java
index ce9ae0e..f1a5355 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeSearchOperationCallbackTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeSearchOperationCallbackTest.java
@@ -55,7 +55,7 @@
                 SerdeUtils.serdesToComparatorFactories(keySerdes, keySerdes.length), bloomFilterKeyFields,
                 harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
                 NoOpOperationTrackerProvider.INSTANCE.getOperationTracker(null), harness.getIOScheduler(),
-                harness.getIOOperationCallbackProvider());
+                harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeUpdateTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeUpdateTest.java
index 6f8ef84..a5097b4 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeUpdateTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/LSMBTreeUpdateTest.java
@@ -54,7 +54,7 @@
         return LSMBTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, numKeys,
                 harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(), harness.getOperationTracker(),
-                harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/multithread/LSMBTreeMultiThreadTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/multithread/LSMBTreeMultiThreadTest.java
index 1ae201f..adee618 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/multithread/LSMBTreeMultiThreadTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/multithread/LSMBTreeMultiThreadTest.java
@@ -53,7 +53,7 @@
         return LSMBTreeUtils.createLSMTree(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), typeTraits, cmpFactories,
                 bloomFilterKeyFields, harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestContext.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestContext.java
index 39e7184..6f7c23a 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestContext.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestContext.java
@@ -28,7 +28,7 @@
 import edu.uci.ics.hyracks.storage.am.common.CheckTuple;
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
 import edu.uci.ics.hyracks.storage.am.lsm.btree.impls.LSMBTree;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -66,8 +66,8 @@
     public static LSMBTreeTestContext create(List<IVirtualBufferCache> virtualBufferCaches, FileReference file,
             IBufferCache diskBufferCache, IFileMapProvider diskFileMapProvider, ISerializerDeserializer[] fieldSerdes,
             int numKeyFields, double bloomFilterFalsePositiveRate, ILSMMergePolicy mergePolicy,
-            ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) throws Exception {
+            ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallback ioOpCallback)
+            throws Exception {
         ITypeTraits[] typeTraits = SerdeUtils.serdesToTypeTraits(fieldSerdes);
         IBinaryComparatorFactory[] cmpFactories = SerdeUtils.serdesToComparatorFactories(fieldSerdes, numKeyFields);
         int[] bloomFilterKeyFields = new int[numKeyFields];
@@ -76,7 +76,7 @@
         }
         LSMBTree lsmTree = LSMBTreeUtils.createLSMTree(virtualBufferCaches, file, diskBufferCache, diskFileMapProvider,
                 typeTraits, cmpFactories, bloomFilterKeyFields, bloomFilterFalsePositiveRate, mergePolicy, opTracker,
-                ioScheduler, ioOpCallbackProvider);
+                ioScheduler, ioOpCallback);
         LSMBTreeTestContext testCtx = new LSMBTreeTestContext(fieldSerdes, lsmTree);
         return testCtx;
     }
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestHarness.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestHarness.java
index 216861f..b88da7b 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestHarness.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestHarness.java
@@ -32,7 +32,7 @@
 import edu.uci.ics.hyracks.control.nc.io.IOManager;
 import edu.uci.ics.hyracks.storage.am.btree.frames.BTreeLeafFrameType;
 import edu.uci.ics.hyracks.storage.am.config.AccessMethodTestsConfig;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -73,7 +73,7 @@
     protected ILSMIOOperationScheduler ioScheduler;
     protected ILSMMergePolicy mergePolicy;
     protected ILSMOperationTracker opTracker;
-    protected ILSMIOOperationCallbackProvider ioOpCallbackProvider;
+    protected ILSMIOOperationCallback ioOpCallback;
 
     protected final Random rnd = new Random();
     protected final static SimpleDateFormat simpleDateFormat = new SimpleDateFormat("ddMMyy-hhmmssSS");
@@ -92,7 +92,7 @@
         this.ioScheduler = SynchronousScheduler.INSTANCE;
         this.mergePolicy = NoMergePolicy.INSTANCE;
         this.opTracker = new ThreadCountingTracker();
-        this.ioOpCallbackProvider = NoOpIOOperationCallback.INSTANCE;
+        this.ioOpCallback = NoOpIOOperationCallback.INSTANCE;
         this.numMutableComponents = AccessMethodTestsConfig.LSM_BTREE_NUM_MUTABLE_COMPONENTS;
     }
 
@@ -206,7 +206,7 @@
         return mergePolicy;
     }
 
-    public ILSMIOOperationCallbackProvider getIOOperationCallbackProvider() {
-        return ioOpCallbackProvider;
+    public ILSMIOOperationCallback getIOOperationCallback() {
+        return ioOpCallback;
     }
 }
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/common/LSMInvertedIndexTestHarness.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/common/LSMInvertedIndexTestHarness.java
index 48176b7..0907fc0 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/common/LSMInvertedIndexTestHarness.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/common/LSMInvertedIndexTestHarness.java
@@ -30,7 +30,7 @@
 import edu.uci.ics.hyracks.api.io.IODeviceHandle;
 import edu.uci.ics.hyracks.control.nc.io.IOManager;
 import edu.uci.ics.hyracks.storage.am.config.AccessMethodTestsConfig;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -69,7 +69,7 @@
     protected ILSMIOOperationScheduler ioScheduler;
     protected ILSMMergePolicy mergePolicy;
     protected ILSMOperationTracker opTracker;
-    protected ILSMIOOperationCallbackProvider ioOpCallbackProvider;
+    protected ILSMIOOperationCallback ioOpCallback;
 
     protected final Random rnd = new Random();
     protected final static SimpleDateFormat simpleDateFormat = new SimpleDateFormat("ddMMyy-hhmmssSS");
@@ -90,7 +90,7 @@
         this.ioScheduler = SynchronousScheduler.INSTANCE;
         this.mergePolicy = NoMergePolicy.INSTANCE;
         this.opTracker = new ThreadCountingTracker();
-        this.ioOpCallbackProvider = NoOpIOOperationCallback.INSTANCE;
+        this.ioOpCallback = NoOpIOOperationCallback.INSTANCE;
         this.numMutableComponents = AccessMethodTestsConfig.LSM_INVINDEX_NUM_MUTABLE_COMPONENTS;
     }
 
@@ -212,7 +212,7 @@
         return mergePolicy;
     }
 
-    public ILSMIOOperationCallbackProvider getIOOperationCallbackProvider() {
-        return ioOpCallbackProvider;
+    public ILSMIOOperationCallback getIOOperationCallback() {
+        return ioOpCallback;
     }
 }
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/util/LSMInvertedIndexTestContext.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/util/LSMInvertedIndexTestContext.java
index 5edf74e..059df73 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/util/LSMInvertedIndexTestContext.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/util/LSMInvertedIndexTestContext.java
@@ -152,8 +152,7 @@
                         harness.getDiskFileMapProvider(), invListTypeTraits, invListCmpFactories, tokenTypeTraits,
                         tokenCmpFactories, tokenizerFactory, harness.getDiskBufferCache(), harness.getOnDiskDir(),
                         harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
-                        harness.getOperationTracker(), harness.getIOScheduler(),
-                        harness.getIOOperationCallbackProvider());
+                        harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
                 break;
             }
             case PARTITIONED_LSM: {
@@ -161,8 +160,7 @@
                         harness.getDiskFileMapProvider(), invListTypeTraits, invListCmpFactories, tokenTypeTraits,
                         tokenCmpFactories, tokenizerFactory, harness.getDiskBufferCache(), harness.getOnDiskDir(),
                         harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
-                        harness.getOperationTracker(), harness.getIOScheduler(),
-                        harness.getIOOperationCallbackProvider());
+                        harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
                 break;
             }
             default: {
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeBulkLoadTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeBulkLoadTest.java
index 09daaab..dadd08c 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeBulkLoadTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeBulkLoadTest.java
@@ -57,7 +57,7 @@
         return LSMRTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, valueProviderFactories,
                 numKeys, rtreePolicyType, harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeDeleteTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeDeleteTest.java
index f5b4ae4..0b92cd3 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeDeleteTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeDeleteTest.java
@@ -57,7 +57,7 @@
         return LSMRTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, valueProviderFactories,
                 numKeys, rtreePolicyType, harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeExamplesTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeExamplesTest.java
index c94bb48..b04ae16 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeExamplesTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeExamplesTest.java
@@ -41,7 +41,7 @@
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), typeTraits, rtreeCmpFactories,
                 btreeCmpFactories, valueProviderFactories, rtreePolicyType, harness.getBoomFilterFalsePositiveRate(),
                 harness.getMergePolicy(), harness.getOperationTracker(), harness.getIOScheduler(),
-                harness.getIOOperationCallbackProvider(),
+                harness.getIOOperationCallback(),
                 LSMRTreeUtils.proposeBestLinearizer(typeTraits, rtreeCmpFactories.length));
     }
 
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeInsertTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeInsertTest.java
index 858f90a..35c6a6b 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeInsertTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeInsertTest.java
@@ -57,7 +57,7 @@
         return LSMRTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, valueProviderFactories,
                 numKeys, rtreePolicyType, harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeLifecycleTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeLifecycleTest.java
index 61692b8..6ef2e94 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeLifecycleTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeLifecycleTest.java
@@ -66,7 +66,7 @@
         testCtx = LSMRTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, valueProviderFactories,
                 numKeys, RTreePolicyType.RTREE, harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
         index = testCtx.getIndex();
     }
 
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeMergeTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeMergeTest.java
index 436f9b1..94528e7 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeMergeTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeMergeTest.java
@@ -56,7 +56,7 @@
         return LSMRTreeTestContext.create(harness.getVirtualBufferCaches(), harness.getFileReference(),
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), fieldSerdes, valueProviderFactories,
                 numKeys, rtreePolicyType, harness.getBoomFilterFalsePositiveRate(), harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesBulkLoadTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesBulkLoadTest.java
index 97a3dcc..22a6eb8 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesBulkLoadTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesBulkLoadTest.java
@@ -57,7 +57,7 @@
         return LSMRTreeWithAntiMatterTuplesTestContext.create(harness.getVirtualBufferCaches(),
                 harness.getFileReference(), harness.getDiskBufferCache(), harness.getDiskFileMapProvider(),
                 fieldSerdes, valueProviderFactories, numKeys, rtreePolicyType, harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesDeleteTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesDeleteTest.java
index 843dcc7..10aec7e 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesDeleteTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesDeleteTest.java
@@ -57,7 +57,7 @@
         return LSMRTreeWithAntiMatterTuplesTestContext.create(harness.getVirtualBufferCaches(),
                 harness.getFileReference(), harness.getDiskBufferCache(), harness.getDiskFileMapProvider(),
                 fieldSerdes, valueProviderFactories, numKeys, rtreePolicyType, harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesExamplesTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesExamplesTest.java
index 6ffa59a..a51abef 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesExamplesTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesExamplesTest.java
@@ -41,7 +41,7 @@
                 harness.getFileReference(), harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), typeTraits,
                 rtreeCmpFactories, btreeCmpFactories, valueProviderFactories, rtreePolicyType,
                 harness.getMergePolicy(), harness.getOperationTracker(), harness.getIOScheduler(),
-                harness.getIOOperationCallbackProvider(),
+                harness.getIOOperationCallback(),
                 LSMRTreeUtils.proposeBestLinearizer(typeTraits, rtreeCmpFactories.length));
     }
 
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesInsertTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesInsertTest.java
index 1e1f46d..e5b33cc 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesInsertTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesInsertTest.java
@@ -57,7 +57,7 @@
         return LSMRTreeWithAntiMatterTuplesTestContext.create(harness.getVirtualBufferCaches(),
                 harness.getFileReference(), harness.getDiskBufferCache(), harness.getDiskFileMapProvider(),
                 fieldSerdes, valueProviderFactories, numKeys, rtreePolicyType, harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesLifecycleTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesLifecycleTest.java
index 607e980..10ae5e1 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesLifecycleTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesLifecycleTest.java
@@ -66,7 +66,7 @@
         testCtx = LSMRTreeWithAntiMatterTuplesTestContext.create(harness.getVirtualBufferCaches(),
                 harness.getFileReference(), harness.getDiskBufferCache(), harness.getDiskFileMapProvider(),
                 fieldSerdes, valueProviderFactories, numKeys, RTreePolicyType.RTREE, harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
         index = testCtx.getIndex();
     }
 
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesMergeTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesMergeTest.java
index bdd80aa..21d3759 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesMergeTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesMergeTest.java
@@ -56,7 +56,7 @@
         return LSMRTreeWithAntiMatterTuplesTestContext.create(harness.getVirtualBufferCaches(),
                 harness.getFileReference(), harness.getDiskBufferCache(), harness.getDiskFileMapProvider(),
                 fieldSerdes, valueProviderFactories, numKeys, rtreePolicyType, harness.getMergePolicy(),
-                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallbackProvider());
+                harness.getOperationTracker(), harness.getIOScheduler(), harness.getIOOperationCallback());
     }
 
     @Override
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeMultiThreadTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeMultiThreadTest.java
index 0c0d804..077bd45 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeMultiThreadTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeMultiThreadTest.java
@@ -61,7 +61,7 @@
                 harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), typeTraits, rtreeCmpFactories,
                 btreeCmpFactories, valueProviderFactories, rtreePolicyType, harness.getBoomFilterFalsePositiveRate(),
                 harness.getMergePolicy(), harness.getOperationTracker(), harness.getIOScheduler(),
-                harness.getIOOperationCallbackProvider(),
+                harness.getIOOperationCallback(),
                 LSMRTreeUtils.proposeBestLinearizer(typeTraits, rtreeCmpFactories.length));
     }
 
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeWithAntiMatterTuplesMultiThreadTest.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeWithAntiMatterTuplesMultiThreadTest.java
index 8b54373..ef871dd 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeWithAntiMatterTuplesMultiThreadTest.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeWithAntiMatterTuplesMultiThreadTest.java
@@ -61,7 +61,7 @@
                 harness.getFileReference(), harness.getDiskBufferCache(), harness.getDiskFileMapProvider(), typeTraits,
                 rtreeCmpFactories, btreeCmpFactories, valueProviderFactories, rtreePolicyType,
                 harness.getMergePolicy(), harness.getOperationTracker(), harness.getIOScheduler(),
-                harness.getIOOperationCallbackProvider(),
+                harness.getIOOperationCallback(),
                 LSMRTreeUtils.proposeBestLinearizer(typeTraits, rtreeCmpFactories.length));
 
     }
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestContext.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestContext.java
index 9536e96..42e793b 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestContext.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestContext.java
@@ -26,7 +26,7 @@
 import edu.uci.ics.hyracks.dataflow.common.util.SerdeUtils;
 import edu.uci.ics.hyracks.storage.am.common.api.IPrimitiveValueProviderFactory;
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -71,8 +71,7 @@
             IBufferCache diskBufferCache, IFileMapProvider diskFileMapProvider, ISerializerDeserializer[] fieldSerdes,
             IPrimitiveValueProviderFactory[] valueProviderFactories, int numKeyFields, RTreePolicyType rtreePolicyType,
             double bloomFilterFalsePositiveRate, ILSMMergePolicy mergePolicy, ILSMOperationTracker opTracker,
-            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallbackProvider ioOpCallbackProvider)
-            throws Exception {
+            ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallback ioOpCallback) throws Exception {
         ITypeTraits[] typeTraits = SerdeUtils.serdesToTypeTraits(fieldSerdes);
         IBinaryComparatorFactory[] rtreeCmpFactories = SerdeUtils
                 .serdesToComparatorFactories(fieldSerdes, numKeyFields);
@@ -80,7 +79,7 @@
                 fieldSerdes.length);
         LSMRTree lsmTree = LSMRTreeUtils.createLSMTree(virtualBufferCaches, file, diskBufferCache, diskFileMapProvider,
                 typeTraits, rtreeCmpFactories, btreeCmpFactories, valueProviderFactories, rtreePolicyType,
-                bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider,
+                bloomFilterFalsePositiveRate, mergePolicy, opTracker, ioScheduler, ioOpCallback,
                 LSMRTreeUtils.proposeBestLinearizer(typeTraits, rtreeCmpFactories.length));
         LSMRTreeTestContext testCtx = new LSMRTreeTestContext(fieldSerdes, lsmTree);
         return testCtx;
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestHarness.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestHarness.java
index b67274e..66e79a2 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestHarness.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestHarness.java
@@ -31,7 +31,7 @@
 import edu.uci.ics.hyracks.api.io.IODeviceHandle;
 import edu.uci.ics.hyracks.control.nc.io.IOManager;
 import edu.uci.ics.hyracks.storage.am.config.AccessMethodTestsConfig;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -68,7 +68,7 @@
     protected List<IVirtualBufferCache> virtualBufferCaches;
     protected IHyracksTaskContext ctx;
     protected ILSMIOOperationScheduler ioScheduler;
-    protected ILSMIOOperationCallbackProvider ioOpCallbackProvider;
+    protected ILSMIOOperationCallback ioOpCallback;
     protected ILSMMergePolicy mergePolicy;
     protected ILSMOperationTracker opTracker;
 
@@ -89,7 +89,7 @@
         this.ioScheduler = SynchronousScheduler.INSTANCE;
         this.mergePolicy = NoMergePolicy.INSTANCE;
         this.opTracker = new ThreadCountingTracker();
-        this.ioOpCallbackProvider = NoOpIOOperationCallback.INSTANCE;
+        this.ioOpCallback = NoOpIOOperationCallback.INSTANCE;
         this.numMutableComponents = AccessMethodTestsConfig.LSM_RTREE_NUM_MUTABLE_COMPONENTS;
     }
 
@@ -206,7 +206,7 @@
         return mergePolicy;
     }
 
-    public ILSMIOOperationCallbackProvider getIOOperationCallbackProvider() {
-        return ioOpCallbackProvider;
+    public ILSMIOOperationCallback getIOOperationCallback() {
+        return ioOpCallback;
     }
 }
diff --git a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeWithAntiMatterTuplesTestContext.java b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeWithAntiMatterTuplesTestContext.java
index 069524c..6a0a6bb 100644
--- a/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeWithAntiMatterTuplesTestContext.java
+++ b/hyracks/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeWithAntiMatterTuplesTestContext.java
@@ -26,7 +26,7 @@
 import edu.uci.ics.hyracks.dataflow.common.util.SerdeUtils;
 import edu.uci.ics.hyracks.storage.am.common.api.IPrimitiveValueProviderFactory;
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTracker;
@@ -72,8 +72,8 @@
             FileReference file, IBufferCache diskBufferCache, IFileMapProvider diskFileMapProvider,
             ISerializerDeserializer[] fieldSerdes, IPrimitiveValueProviderFactory[] valueProviderFactories,
             int numKeyFields, RTreePolicyType rtreePolicyType, ILSMMergePolicy mergePolicy,
-            ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler,
-            ILSMIOOperationCallbackProvider ioOpCallbackProvider) throws Exception {
+            ILSMOperationTracker opTracker, ILSMIOOperationScheduler ioScheduler, ILSMIOOperationCallback ioOpCallback)
+            throws Exception {
         ITypeTraits[] typeTraits = SerdeUtils.serdesToTypeTraits(fieldSerdes);
         IBinaryComparatorFactory[] rtreeCmpFactories = SerdeUtils
                 .serdesToComparatorFactories(fieldSerdes, numKeyFields);
@@ -81,7 +81,7 @@
                 fieldSerdes.length);
         LSMRTreeWithAntiMatterTuples lsmTree = LSMRTreeUtils.createLSMTreeWithAntiMatterTuples(virtualBufferCaches,
                 file, diskBufferCache, diskFileMapProvider, typeTraits, rtreeCmpFactories, btreeCmpFactories,
-                valueProviderFactories, rtreePolicyType, mergePolicy, opTracker, ioScheduler, ioOpCallbackProvider,
+                valueProviderFactories, rtreePolicyType, mergePolicy, opTracker, ioScheduler, ioOpCallback,
                 LSMRTreeUtils.proposeBestLinearizer(typeTraits, rtreeCmpFactories.length));
         LSMRTreeWithAntiMatterTuplesTestContext testCtx = new LSMRTreeWithAntiMatterTuplesTestContext(fieldSerdes,
                 lsmTree);