diff --git a/hyracks/hyracks-control/hyracks-control-nc/src/main/java/edu/uci/ics/hyracks/control/nc/work/NotifyTaskFailureWork.java b/hyracks/hyracks-control/hyracks-control-nc/src/main/java/edu/uci/ics/hyracks/control/nc/work/NotifyTaskFailureWork.java
index c4784ff..f5fb6f8 100644
--- a/hyracks/hyracks-control/hyracks-control-nc/src/main/java/edu/uci/ics/hyracks/control/nc/work/NotifyTaskFailureWork.java
+++ b/hyracks/hyracks-control/hyracks-control-nc/src/main/java/edu/uci/ics/hyracks/control/nc/work/NotifyTaskFailureWork.java
@@ -43,6 +43,7 @@
                 dpm.abortReader(jobId);
             }
             ncs.getClusterController().notifyTaskFailure(jobId, task.getTaskAttemptId(), ncs.getId(), exceptions);
+            exceptions.get(0).printStackTrace();
         } catch (Exception e) {
             e.printStackTrace();
         }
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java
index 0b75446..478ac07 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGen.java
@@ -494,7 +494,7 @@
                     NoOpIOOperationCallback.INSTANCE, 0.01);
         } else {
             return new BTreeDataflowHelperFactory();
-        }
+       }
     }
 
     /** generate non-first iteration job */
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopJoinFunctionUpdateOperatorNodePushable.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopJoinFunctionUpdateOperatorNodePushable.java
index 238b775..90c0c84 100644
--- a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopJoinFunctionUpdateOperatorNodePushable.java
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopJoinFunctionUpdateOperatorNodePushable.java
@@ -33,7 +33,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IIndexCursor;
 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.TreeIndexDataflowHelper;
+import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallback;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.common.tuples.PermutingFrameTupleReference;
@@ -46,7 +46,7 @@
 import edu.uci.ics.pregelix.dataflow.util.UpdateBuffer;
 
 public class IndexNestedLoopJoinFunctionUpdateOperatorNodePushable extends AbstractUnaryInputOperatorNodePushable {
-    private TreeIndexDataflowHelper treeIndexOpHelper;
+    private IndexDataflowHelper treeIndexOpHelper;
     private FrameTupleAccessor accessor;
 
     private ByteBuffer writeBuffer;
@@ -74,7 +74,7 @@
             int[] lowKeyFields, int[] highKeyFields, boolean lowKeyInclusive, boolean highKeyInclusive,
             IUpdateFunctionFactory functionFactory, IRuntimeHookFactory preHookFactory,
             IRuntimeHookFactory postHookFactory, IRecordDescriptorFactory inputRdFactory, int outputArity) {
-        treeIndexOpHelper = (TreeIndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
+        treeIndexOpHelper = (IndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
                 opDesc, ctx, partition);
         this.lowKeyInclusive = lowKeyInclusive;
         this.highKeyInclusive = highKeyInclusive;
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopJoinOperatorNodePushable.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopJoinOperatorNodePushable.java
index 221a818..2ddca90 100644
--- a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopJoinOperatorNodePushable.java
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopJoinOperatorNodePushable.java
@@ -34,13 +34,13 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IIndexCursor;
 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.TreeIndexDataflowHelper;
+import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallback;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.common.tuples.PermutingFrameTupleReference;
 
 public class IndexNestedLoopJoinOperatorNodePushable extends AbstractUnaryInputUnaryOutputOperatorNodePushable {
-    private TreeIndexDataflowHelper treeIndexOpHelper;
+    private IndexDataflowHelper treeIndexOpHelper;
     private FrameTupleAccessor accessor;
 
     private ByteBuffer writeBuffer;
@@ -66,7 +66,7 @@
             int partition, IRecordDescriptorProvider recordDescProvider, boolean isForward, int[] lowKeyFields,
             int[] highKeyFields, boolean lowKeyInclusive, boolean highKeyInclusive) {
         inputRecDesc = recordDescProvider.getInputRecordDescriptor(opDesc.getActivityId(), 0);
-        treeIndexOpHelper = (TreeIndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
+        treeIndexOpHelper = (IndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
                 opDesc, ctx, partition);
         this.lowKeyInclusive = lowKeyInclusive;
         this.highKeyInclusive = highKeyInclusive;
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopRightOuterJoinFunctionUpdateOperatorNodePushable.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopRightOuterJoinFunctionUpdateOperatorNodePushable.java
index 06119ea..b817987 100644
--- a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopRightOuterJoinFunctionUpdateOperatorNodePushable.java
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopRightOuterJoinFunctionUpdateOperatorNodePushable.java
@@ -35,7 +35,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IIndexCursor;
 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.TreeIndexDataflowHelper;
+import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallback;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.common.tuples.PermutingFrameTupleReference;
@@ -49,7 +49,7 @@
 
 public class IndexNestedLoopRightOuterJoinFunctionUpdateOperatorNodePushable extends
         AbstractUnaryInputOperatorNodePushable {
-    private TreeIndexDataflowHelper treeIndexOpHelper;
+    private IndexDataflowHelper treeIndexOpHelper;
     private FrameTupleAccessor accessor;
 
     private ByteBuffer writeBuffer;
@@ -86,7 +86,7 @@
             IRuntimeHookFactory preHookFactory, IRuntimeHookFactory postHookFactory,
             IRecordDescriptorFactory inputRdFactory, int outputArity) {
         inputRecDesc = recordDescProvider.getInputRecordDescriptor(opDesc.getActivityId(), 0);
-        treeIndexOpHelper = (TreeIndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
+        treeIndexOpHelper = (IndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
                 opDesc, ctx, partition);
         this.recDesc = recordDescProvider.getInputRecordDescriptor(opDesc.getActivityId(), 0);
 
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopRightOuterJoinOperatorNodePushable.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopRightOuterJoinOperatorNodePushable.java
index 48812b7..204d8ce 100644
--- a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopRightOuterJoinOperatorNodePushable.java
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopRightOuterJoinOperatorNodePushable.java
@@ -35,14 +35,14 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IIndexCursor;
 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.TreeIndexDataflowHelper;
+import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallback;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.common.tuples.PermutingFrameTupleReference;
 
 public class IndexNestedLoopRightOuterJoinOperatorNodePushable extends
         AbstractUnaryInputUnaryOutputOperatorNodePushable {
-    private TreeIndexDataflowHelper treeIndexOpHelper;
+    private IndexDataflowHelper treeIndexOpHelper;
     private FrameTupleAccessor accessor;
 
     private ByteBuffer writeBuffer;
@@ -72,7 +72,7 @@
             IHyracksTaskContext ctx, int partition, IRecordDescriptorProvider recordDescProvider, boolean isForward,
             int[] lowKeyFields, int[] highKeyFields, INullWriter[] nullWriter) {
         inputRecDesc = recordDescProvider.getInputRecordDescriptor(opDesc.getActivityId(), 0);
-        treeIndexOpHelper = (TreeIndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
+        treeIndexOpHelper = (IndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
                 opDesc, ctx, partition);
         this.isForward = isForward;
         this.recDesc = recordDescProvider.getInputRecordDescriptor(opDesc.getActivityId(), 0);
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopSetUnionFunctionUpdateOperatorNodePushable.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopSetUnionFunctionUpdateOperatorNodePushable.java
index ee821df..bdf90e4 100644
--- a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopSetUnionFunctionUpdateOperatorNodePushable.java
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopSetUnionFunctionUpdateOperatorNodePushable.java
@@ -33,7 +33,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IIndexCursor;
 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.TreeIndexDataflowHelper;
+import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallback;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.common.tuples.PermutingFrameTupleReference;
@@ -46,7 +46,7 @@
 import edu.uci.ics.pregelix.dataflow.util.UpdateBuffer;
 
 public class IndexNestedLoopSetUnionFunctionUpdateOperatorNodePushable extends AbstractUnaryInputOperatorNodePushable {
-    private TreeIndexDataflowHelper treeIndexOpHelper;
+    private IndexDataflowHelper treeIndexOpHelper;
     private FrameTupleAccessor accessor;
 
     private ByteBuffer writeBuffer;
@@ -77,7 +77,7 @@
             int[] lowKeyFields, int[] highKeyFields, IUpdateFunctionFactory functionFactory,
             IRuntimeHookFactory preHookFactory, IRuntimeHookFactory postHookFactory,
             IRecordDescriptorFactory inputRdFactory, int outputArity) {
-        treeIndexOpHelper = (TreeIndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
+        treeIndexOpHelper = (IndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
                 opDesc, ctx, partition);
         this.isForward = isForward;
         this.recDesc = recordDescProvider.getInputRecordDescriptor(opDesc.getActivityId(), 0);
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopSetUnionOperatorNodePushable.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopSetUnionOperatorNodePushable.java
index d6f95f9..bbe2764 100644
--- a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopSetUnionOperatorNodePushable.java
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/IndexNestedLoopSetUnionOperatorNodePushable.java
@@ -34,13 +34,13 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IIndexCursor;
 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.TreeIndexDataflowHelper;
+import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallback;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.common.tuples.PermutingFrameTupleReference;
 
 public class IndexNestedLoopSetUnionOperatorNodePushable extends AbstractUnaryInputUnaryOutputOperatorNodePushable {
-    private TreeIndexDataflowHelper treeIndexOpHelper;
+    private IndexDataflowHelper treeIndexOpHelper;
     private FrameTupleAccessor accessor;
 
     private ByteBuffer writeBuffer;
@@ -67,7 +67,7 @@
             IHyracksTaskContext ctx, int partition, IRecordDescriptorProvider recordDescProvider, boolean isForward,
             int[] lowKeyFields, int[] highKeyFields) {
         inputRecDesc = recordDescProvider.getInputRecordDescriptor(opDesc.getActivityId(), 0);
-        treeIndexOpHelper = (TreeIndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
+        treeIndexOpHelper = (IndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
                 opDesc, ctx, partition);
         this.recDesc = recordDescProvider.getInputRecordDescriptor(opDesc.getActivityId(), 0);
 
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/TreeIndexBulkReLoadOperatorNodePushable.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/TreeIndexBulkReLoadOperatorNodePushable.java
index e3d89d5..d5ea7ac 100644
--- a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/TreeIndexBulkReLoadOperatorNodePushable.java
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/TreeIndexBulkReLoadOperatorNodePushable.java
@@ -29,13 +29,13 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IndexException;
 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.common.dataflow.TreeIndexDataflowHelper;
+import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
 import edu.uci.ics.hyracks.storage.am.common.tuples.PermutingFrameTupleReference;
 import edu.uci.ics.hyracks.storage.common.IStorageManagerInterface;
 
 public class TreeIndexBulkReLoadOperatorNodePushable extends AbstractUnaryInputSinkOperatorNodePushable {
     private final float fillFactor;
-    private final TreeIndexDataflowHelper treeIndexOpHelper;
+    private final IndexDataflowHelper treeIndexOpHelper;
     private final IIndexOperatorDescriptor opDesc;
     private final IRecordDescriptorProvider recordDescProvider;
     private final PermutingFrameTupleReference tuple = new PermutingFrameTupleReference();
@@ -49,7 +49,7 @@
             IStorageManagerInterface storageManager, IIndexLifecycleManagerProvider lcManagerProvider,
             IFileSplitProvider fileSplitProvider) {
         this.fillFactor = fillFactor;
-        treeIndexOpHelper = (TreeIndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
+        treeIndexOpHelper = (IndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
                 opDesc, ctx, partition);
         this.opDesc = opDesc;
         this.recordDescProvider = recordDescProvider;
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/TreeSearchFunctionUpdateOperatorNodePushable.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/TreeSearchFunctionUpdateOperatorNodePushable.java
index 13aab31..f6193bb 100644
--- a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/TreeSearchFunctionUpdateOperatorNodePushable.java
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/std/TreeSearchFunctionUpdateOperatorNodePushable.java
@@ -34,7 +34,7 @@
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndexFrame;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.AbstractTreeIndexOperatorDescriptor;
-import edu.uci.ics.hyracks.storage.am.common.dataflow.TreeIndexDataflowHelper;
+import edu.uci.ics.hyracks.storage.am.common.dataflow.IndexDataflowHelper;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallback;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.common.tuples.PermutingFrameTupleReference;
@@ -47,7 +47,7 @@
 import edu.uci.ics.pregelix.dataflow.util.UpdateBuffer;
 
 public class TreeSearchFunctionUpdateOperatorNodePushable extends AbstractUnaryInputOperatorNodePushable {
-    protected TreeIndexDataflowHelper treeIndexHelper;
+    protected IndexDataflowHelper treeIndexHelper;
     protected FrameTupleAccessor accessor;
 
     protected ByteBuffer writeBuffer;
@@ -83,7 +83,7 @@
             int[] lowKeyFields, int[] highKeyFields, boolean lowKeyInclusive, boolean highKeyInclusive,
             IUpdateFunctionFactory functionFactory, IRuntimeHookFactory preHookFactory,
             IRuntimeHookFactory postHookFactory, IRecordDescriptorFactory inputRdFactory, int outputArity) {
-        treeIndexHelper = (TreeIndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
+        treeIndexHelper = (IndexDataflowHelper) opDesc.getIndexDataflowHelperFactory().createIndexDataflowHelper(
                 opDesc, ctx, partition);
         this.isForward = isForward;
         this.lowKeyInclusive = lowKeyInclusive;
@@ -142,7 +142,7 @@
                 }
                 highKeySearchCmp = new MultiComparator(highKeySearchComparators);
             }
-            
+
             rangePred = new RangePredicate(null, null, lowKeyInclusive, highKeyInclusive, lowKeySearchCmp,
                     highKeySearchCmp);