diff --git a/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/PushSimilarityFunctionsBelowJoin.java b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/PushSimilarityFunctionsBelowJoin.java
new file mode 100644
index 0000000..69a5fb5
--- /dev/null
+++ b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/PushSimilarityFunctionsBelowJoin.java
@@ -0,0 +1,214 @@
+/*
+ * Copyright 2009-2012 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.asterix.optimizer.rules;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+
+import org.apache.commons.lang3.mutable.Mutable;
+import org.apache.commons.lang3.mutable.MutableObject;
+
+import edu.uci.ics.asterix.om.functions.AsterixBuiltinFunctions;
+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.ILogicalOperator;
+import edu.uci.ics.hyracks.algebricks.core.algebra.base.IOptimizationContext;
+import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalExpressionTag;
+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.AbstractFunctionCallExpression;
+import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.AbstractLogicalExpression;
+import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.VariableReferenceExpression;
+import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
+import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AbstractBinaryJoinOperator;
+import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
+import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AssignOperator;
+import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.visitors.VariableUtilities;
+import edu.uci.ics.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
+
+/**
+ * Pushes similarity function-call expressions below a join if possible.
+ * Assigns the similarity function-call expressions to new variables, and replaces the original
+ * expression with a corresponding variable reference expression.
+ * This rule can help reduce the cost of computing expensive similarity functions by pushing them below
+ * a join (which may blow up the cardinality).
+ * Also, this rule may help to enable other rules such as common subexpression elimination, again to reduce
+ * the number of calls to expensive similarity functions.
+ * 
+ * Example:
+ * 
+ * Before plan:
+ * assign [$$10] <- [funcA(funcB(simFuncX($$3, $$4)))]
+ *   join (some condition) 
+ *     join_branch_0 where $$3 and $$4 are not live
+ *       ...
+ *     join_branch_1 where $$3 and $$4 are live
+ *       ...
+ * 
+ * After plan:
+ * assign [$$10] <- [funcA(funcB($$11))]
+ *   join (some condition) 
+ *     join_branch_0 where $$3 and $$4 are not live
+ *       ...
+ *     join_branch_1 where $$3 and $$4 are live
+ *       assign[$$11] <- [simFuncX($$3, $$4)]
+ *         ...
+ */
+public class PushSimilarityFunctionsBelowJoin implements IAlgebraicRewriteRule {
+
+    private static final Set<FunctionIdentifier> simFuncIdents = new HashSet<FunctionIdentifier>();
+    static {
+        simFuncIdents.add(AsterixBuiltinFunctions.SIMILARITY_JACCARD);
+        simFuncIdents.add(AsterixBuiltinFunctions.SIMILARITY_JACCARD_CHECK);
+        simFuncIdents.add(AsterixBuiltinFunctions.EDIT_DISTANCE);
+        simFuncIdents.add(AsterixBuiltinFunctions.EDIT_DISTANCE_CHECK);
+    }
+
+    private final List<Mutable<ILogicalExpression>> simFuncExprs = new ArrayList<Mutable<ILogicalExpression>>();
+    private final List<LogicalVariable> usedVars = new ArrayList<LogicalVariable>();
+    private final List<LogicalVariable> liveVars = new ArrayList<LogicalVariable>();
+
+    @Override
+    public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context) throws AlgebricksException {
+        return false;
+    }
+
+    @Override
+    public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
+            throws AlgebricksException {
+        AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
+        if (op.getOperatorTag() != LogicalOperatorTag.ASSIGN) {
+            return false;
+        }
+        AssignOperator assignOp = (AssignOperator) op;
+
+        // Find a join operator below this assign.
+        Mutable<ILogicalOperator> joinOpRef = findJoinOp(assignOp.getInputs().get(0));
+        if (joinOpRef == null) {
+            return false;
+        }
+        AbstractBinaryJoinOperator joinOp = (AbstractBinaryJoinOperator) joinOpRef.getValue();
+
+        // Check if the assign uses a similarity function that we wish to push below the join if possible.
+        simFuncExprs.clear();
+        gatherSimilarityFunctionCalls(assignOp, simFuncExprs);
+        if (simFuncExprs.isEmpty()) {
+            return false;
+        }
+
+        // Try to push the similarity functions down the input branches of the join.
+        boolean modified = false;
+        if (pushDownSimilarityFunctions(joinOp, 0, simFuncExprs, context)) {
+            modified = true;
+        }
+        if (pushDownSimilarityFunctions(joinOp, 1, simFuncExprs, context)) {
+            modified = true;
+        }
+        if (modified) {
+            context.computeAndSetTypeEnvironmentForOperator(joinOp);
+        }
+        return modified;
+    }
+
+    private Mutable<ILogicalOperator> findJoinOp(Mutable<ILogicalOperator> opRef) {
+        AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
+        switch (op.getOperatorTag()) {
+            case INNERJOIN:
+            case LEFTOUTERJOIN: {
+                return opRef;
+            }
+            // Bail on these operators.
+            case GROUP:
+            case AGGREGATE:
+            case DISTINCT:
+            case UNNEST_MAP: {
+                return null;
+            }
+            // Traverse children.
+            default: {
+                for (Mutable<ILogicalOperator> childOpRef : op.getInputs()) {
+                    return findJoinOp(childOpRef);
+                }
+            }
+        }
+        return null;
+    }
+
+    private void gatherSimilarityFunctionCalls(AssignOperator assignOp, List<Mutable<ILogicalExpression>> simFuncExprs) {
+        for (Mutable<ILogicalExpression> exprRef : assignOp.getExpressions()) {
+            gatherSimilarityFunctionCalls(exprRef, simFuncExprs);
+        }
+    }
+
+    private void gatherSimilarityFunctionCalls(Mutable<ILogicalExpression> exprRef,
+            List<Mutable<ILogicalExpression>> simFuncExprs) {
+        AbstractLogicalExpression expr = (AbstractLogicalExpression) exprRef.getValue();
+        if (expr.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) {
+            return;
+        }
+        // Check whether the function is a similarity function.
+        AbstractFunctionCallExpression funcExpr = (AbstractFunctionCallExpression) expr;
+        if (simFuncIdents.contains(funcExpr.getFunctionIdentifier())) {
+            simFuncExprs.add(exprRef);
+        }
+        // Traverse arguments.
+        for (Mutable<ILogicalExpression> funcArg : funcExpr.getArguments()) {
+            gatherSimilarityFunctionCalls(funcArg, simFuncExprs);
+        }
+    }
+
+    private boolean pushDownSimilarityFunctions(AbstractBinaryJoinOperator joinOp, int inputIndex,
+            List<Mutable<ILogicalExpression>> simFuncExprs, IOptimizationContext context) throws AlgebricksException {
+        ILogicalOperator joinInputOp = joinOp.getInputs().get(inputIndex).getValue();
+        liveVars.clear();
+        VariableUtilities.getLiveVariables(joinInputOp, liveVars);
+        Iterator<Mutable<ILogicalExpression>> simFuncIter = simFuncExprs.iterator();
+        List<LogicalVariable> assignVars = null;
+        List<Mutable<ILogicalExpression>> assignExprs = null;
+        while (simFuncIter.hasNext()) {
+            Mutable<ILogicalExpression> simFuncExprRef = simFuncIter.next();
+            ILogicalExpression simFuncExpr = simFuncExprRef.getValue();
+            usedVars.clear();
+            simFuncExpr.getUsedVariables(usedVars);
+            // Check if we can push the similarity function down this branch.
+            if (liveVars.containsAll(usedVars)) {
+                if (assignVars == null) {
+                    assignVars = new ArrayList<LogicalVariable>();
+                    assignExprs = new ArrayList<Mutable<ILogicalExpression>>();
+                }
+                // Replace the original expression with a variable reference expression.
+                LogicalVariable replacementVar = context.newVar();
+                assignVars.add(replacementVar);
+                assignExprs.add(new MutableObject<ILogicalExpression>(simFuncExpr));
+                simFuncExprRef.setValue(new VariableReferenceExpression(replacementVar));
+                simFuncIter.remove();
+            }
+        }
+        // Create new assign operator below the join if any similarity functions can be pushed.
+        if (assignVars != null) {
+            AssignOperator newAssign = new AssignOperator(assignVars, assignExprs);
+            newAssign.getInputs().add(new MutableObject<ILogicalOperator>(joinInputOp));
+            newAssign.setExecutionMode(joinOp.getExecutionMode());
+            joinOp.getInputs().get(inputIndex).setValue(newAssign);
+            context.computeAndSetTypeEnvironmentForOperator(newAssign);
+            return true;
+        }
+        return false;
+    }
+}
diff --git a/asterix-app/src/test/resources/optimizerts/only.txt b/asterix-app/src/test/resources/optimizerts/only.txt
index 529ccf8..e69de29 100644
--- a/asterix-app/src/test/resources/optimizerts/only.txt
+++ b/asterix-app/src/test/resources/optimizerts/only.txt
@@ -1 +0,0 @@
-inverted-index-join/ngram-edit-distance_04.aql
\ No newline at end of file