diff --git a/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/IntroduceGroupByForSubplanRule.java b/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/IntroduceGroupByForSubplanRule.java
index 67e8d42a3..34dde2a56 100644
--- a/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/IntroduceGroupByForSubplanRule.java
+++ b/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/IntroduceGroupByForSubplanRule.java
@@ -295,9 +295,11 @@ protected Set<LogicalVariable> computeGbyVars(AbstractLogicalOperator op, Set<Lo
         List<LogicalVariable> all = new ArrayList<LogicalVariable>();
         VariableUtilities.getLiveVariables(op, all);
         all.retainAll(freeVars);
-        for (FunctionalDependency fd : fdList) {
-            if (fd.getTail().containsAll(all)) {
-                return new HashSet<LogicalVariable>(fd.getHead());
+        if (!all.isEmpty()) {
+            for (FunctionalDependency fd : fdList) {
+                if (fd.getTail().containsAll(all)) {
+                    return new HashSet<LogicalVariable>(fd.getHead());
+                }
             }
         }
         return null;
diff --git a/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignDownThroughProductRule.java b/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignDownThroughJoinRule.java
similarity index 93%
rename from algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignDownThroughProductRule.java
rename to algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignDownThroughJoinRule.java
index f3f0e0242..4ea2480a2 100644
--- a/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignDownThroughProductRule.java
+++ b/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignDownThroughJoinRule.java
@@ -34,7 +34,7 @@
 import org.apache.hyracks.algebricks.core.algebra.operators.logical.visitors.VariableUtilities;
 import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
 
-public class PushAssignDownThroughProductRule implements IAlgebraicRewriteRule {
+public class PushAssignDownThroughJoinRule implements IAlgebraicRewriteRule {
 
     @Override
     public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context) throws AlgebricksException {
@@ -53,10 +53,10 @@ public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext
         if (op2.getOperatorTag() != LogicalOperatorTag.INNERJOIN) {
             return false;
         }
-        AbstractBinaryJoinOperator join = (AbstractBinaryJoinOperator) op2;
-        if (join.getCondition().getValue() != ConstantExpression.TRUE) {
-            return false;
-        }
+//        AbstractBinaryJoinOperator join = (AbstractBinaryJoinOperator) op2;
+//        if (join.getCondition().getValue() != ConstantExpression.TRUE) {
+//            return false;
+//        }
 
         List<LogicalVariable> used = new ArrayList<LogicalVariable>();
         VariableUtilities.getUsedVariables(op1, used);