diff --git a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/ExtensionOperator.java b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/ExtensionOperator.java
index 97c4097..a1e8a87 100644
--- a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/ExtensionOperator.java
+++ b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/ExtensionOperator.java
@@ -113,4 +113,8 @@
         return delegate.toString();
     }
 
+    public IOperatorExtension getDelegate() {
+        return delegate;
+    }
+
 }
diff --git a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/IOperatorExtension.java b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/IOperatorExtension.java
index 0681b6b..0a80337 100644
--- a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/IOperatorExtension.java
+++ b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/IOperatorExtension.java
@@ -14,6 +14,7 @@
  */
 package edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical;
 
+import java.util.Collection;
 import java.util.List;
 
 import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
@@ -42,4 +43,8 @@
     void setPhysicalOperator(IPhysicalOperator physicalOperator);
 
     ExecutionMode getExecutionMode();
+    
+    public void getUsedVariables(Collection<LogicalVariable> usedVars);
+    
+    public void getProducedVariables(Collection<LogicalVariable> producedVars);
 }
diff --git a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/ProducedVariableVisitor.java b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/ProducedVariableVisitor.java
index 994c6cb..78b6801 100644
--- a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/ProducedVariableVisitor.java
+++ b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/ProducedVariableVisitor.java
@@ -249,6 +249,7 @@
 
     @Override
     public Void visitExtensionOperator(ExtensionOperator op, Void arg) throws AlgebricksException {
+        op.getDelegate().getProducedVariables(producedVariables);
         return null;
     }
 }
diff --git a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/UsedVariableVisitor.java b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/UsedVariableVisitor.java
index 8fed84f..0ea9367 100644
--- a/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/UsedVariableVisitor.java
+++ b/hyracks-algebricks/hyracks-algebricks-core/src/main/java/edu/uci/ics/hyracks/algebricks/core/algebra/operators/logical/visitors/UsedVariableVisitor.java
@@ -344,6 +344,7 @@
 
     @Override
     public Void visitExtensionOperator(ExtensionOperator op, Void arg) throws AlgebricksException {
+        op.getDelegate().getUsedVariables(usedVariables);
         return null;
     }