diff --git a/pregelix/pregelix-dataflow-std/pom.xml b/pregelix/pregelix-dataflow-std/pom.xml
index 3604e57..9ec8e1d 100644
--- a/pregelix/pregelix-dataflow-std/pom.xml
+++ b/pregelix/pregelix-dataflow-std/pom.xml
@@ -21,7 +21,7 @@
 	<parent>
 		<groupId>edu.uci.ics.hyracks</groupId>
 		<artifactId>pregelix</artifactId>
-		<version>0.2.7-SNAPSHOT</version>
+		<version>0.2.10-SNAPSHOT</version>
 	</parent>
 
 
@@ -88,84 +88,84 @@
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>pregelix-dataflow-std-base</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-dataflow-std</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-api</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-dataflow-common</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-data-std</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-hdfs-core</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-storage-am-common</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-storage-am-btree</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-storage-am-lsm-btree</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-control-cc</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-control-nc</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>hyracks-ipc</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<type>jar</type>
 			<scope>compile</scope>
 		</dependency>
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/ClusteredGroupOperatorDescriptor.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/ClusteredGroupOperatorDescriptor.java
new file mode 100644
index 0000000..bb41953
--- /dev/null
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/ClusteredGroupOperatorDescriptor.java
@@ -0,0 +1,50 @@
+/*
+ * 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.pregelix.dataflow.group;
+
+import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
+import edu.uci.ics.hyracks.api.dataflow.IOperatorNodePushable;
+import edu.uci.ics.hyracks.api.dataflow.value.IBinaryComparatorFactory;
+import edu.uci.ics.hyracks.api.dataflow.value.IRecordDescriptorProvider;
+import edu.uci.ics.hyracks.api.dataflow.value.RecordDescriptor;
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
+import edu.uci.ics.hyracks.api.job.IOperatorDescriptorRegistry;
+import edu.uci.ics.hyracks.dataflow.std.base.AbstractSingleActivityOperatorDescriptor;
+
+public class ClusteredGroupOperatorDescriptor extends AbstractSingleActivityOperatorDescriptor {
+    private final int[] groupFields;
+    private final IBinaryComparatorFactory[] comparatorFactories;
+    private final IClusteredAggregatorDescriptorFactory aggregatorFactory;
+
+    private static final long serialVersionUID = 1L;
+
+    public ClusteredGroupOperatorDescriptor(IOperatorDescriptorRegistry spec, int[] groupFields,
+            IBinaryComparatorFactory[] comparatorFactories, IClusteredAggregatorDescriptorFactory aggregatorFactory,
+            RecordDescriptor recordDescriptor) {
+        super(spec, 1, 1);
+        this.groupFields = groupFields;
+        this.comparatorFactories = comparatorFactories;
+        this.aggregatorFactory = aggregatorFactory;
+        recordDescriptors[0] = recordDescriptor;
+    }
+
+    @Override
+    public IOperatorNodePushable createPushRuntime(final IHyracksTaskContext ctx,
+            final IRecordDescriptorProvider recordDescProvider, int partition, int nPartitions)
+            throws HyracksDataException {
+        return new ClusteredGroupOperatorNodePushable(ctx, groupFields, comparatorFactories, aggregatorFactory,
+                recordDescProvider.getInputRecordDescriptor(getActivityId(), 0), recordDescriptors[0]);
+    }
+}
\ No newline at end of file
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/ClusteredGroupOperatorNodePushable.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/ClusteredGroupOperatorNodePushable.java
new file mode 100644
index 0000000..a95a46e
--- /dev/null
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/ClusteredGroupOperatorNodePushable.java
@@ -0,0 +1,79 @@
+/*
+ * 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.pregelix.dataflow.group;
+
+import java.nio.ByteBuffer;
+
+import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
+import edu.uci.ics.hyracks.api.dataflow.value.IBinaryComparator;
+import edu.uci.ics.hyracks.api.dataflow.value.IBinaryComparatorFactory;
+import edu.uci.ics.hyracks.api.dataflow.value.RecordDescriptor;
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
+import edu.uci.ics.hyracks.dataflow.common.comm.io.FrameTupleAccessor;
+import edu.uci.ics.hyracks.dataflow.common.comm.io.FrameTupleAppender;
+import edu.uci.ics.hyracks.dataflow.std.base.AbstractUnaryInputUnaryOutputOperatorNodePushable;
+
+class ClusteredGroupOperatorNodePushable extends AbstractUnaryInputUnaryOutputOperatorNodePushable {
+    private final IHyracksTaskContext ctx;
+    private final int[] groupFields;
+    private final IBinaryComparatorFactory[] comparatorFactories;
+    private final IClusteredAggregatorDescriptorFactory aggregatorFactory;
+    private final RecordDescriptor inRecordDescriptor;
+    private final RecordDescriptor outRecordDescriptor;
+    private ClusteredGroupWriter pgw;
+
+    ClusteredGroupOperatorNodePushable(IHyracksTaskContext ctx, int[] groupFields,
+            IBinaryComparatorFactory[] comparatorFactories, IClusteredAggregatorDescriptorFactory aggregatorFactory,
+            RecordDescriptor inRecordDescriptor, RecordDescriptor outRecordDescriptor) {
+        this.ctx = ctx;
+        this.groupFields = groupFields;
+        this.comparatorFactories = comparatorFactories;
+        this.aggregatorFactory = aggregatorFactory;
+        this.inRecordDescriptor = inRecordDescriptor;
+        this.outRecordDescriptor = outRecordDescriptor;
+    }
+
+    @Override
+    public void open() throws HyracksDataException {
+        final IBinaryComparator[] comparators = new IBinaryComparator[comparatorFactories.length];
+        for (int i = 0; i < comparatorFactories.length; ++i) {
+            comparators[i] = comparatorFactories[i].createBinaryComparator();
+        }
+        final ByteBuffer copyFrame = ctx.allocateFrame();
+        final FrameTupleAccessor copyFrameAccessor = new FrameTupleAccessor(ctx.getFrameSize(), inRecordDescriptor);
+        copyFrameAccessor.reset(copyFrame);
+        ByteBuffer outFrame = ctx.allocateFrame();
+        final FrameTupleAppender appender = new FrameTupleAppender(ctx.getFrameSize());
+        appender.reset(outFrame, true);
+        pgw = new ClusteredGroupWriter(ctx, groupFields, comparators, aggregatorFactory, inRecordDescriptor,
+                outRecordDescriptor, writer);
+        pgw.open();
+    }
+
+    @Override
+    public void nextFrame(ByteBuffer buffer) throws HyracksDataException {
+        pgw.nextFrame(buffer);
+    }
+
+    @Override
+    public void fail() throws HyracksDataException {
+        pgw.fail();
+    }
+
+    @Override
+    public void close() throws HyracksDataException {
+        pgw.close();
+    }
+}
\ No newline at end of file
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/ClusteredGroupWriter.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/ClusteredGroupWriter.java
new file mode 100644
index 0000000..4b4a1c3
--- /dev/null
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/ClusteredGroupWriter.java
@@ -0,0 +1,165 @@
+/*
+ * 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.pregelix.dataflow.group;
+
+import java.nio.ByteBuffer;
+
+import edu.uci.ics.hyracks.api.comm.IFrameWriter;
+import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
+import edu.uci.ics.hyracks.api.dataflow.value.IBinaryComparator;
+import edu.uci.ics.hyracks.api.dataflow.value.RecordDescriptor;
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
+import edu.uci.ics.hyracks.dataflow.common.comm.io.ArrayTupleBuilder;
+import edu.uci.ics.hyracks.dataflow.common.comm.io.FrameTupleAccessor;
+import edu.uci.ics.hyracks.dataflow.common.comm.io.FrameTupleAppender;
+import edu.uci.ics.hyracks.dataflow.common.comm.util.FrameUtils;
+import edu.uci.ics.hyracks.dataflow.std.group.AggregateState;
+import edu.uci.ics.hyracks.dataflow.std.group.IAggregatorDescriptor;
+
+public class ClusteredGroupWriter implements IFrameWriter {
+    private final int[] groupFields;
+    private final IBinaryComparator[] comparators;
+    private final IAggregatorDescriptor aggregator;
+    private final AggregateState aggregateState;
+    private final IFrameWriter writer;
+    private final ByteBuffer copyFrame;
+    private final FrameTupleAccessor inFrameAccessor;
+    private final FrameTupleAccessor copyFrameAccessor;
+
+    private final ByteBuffer outFrame;
+    private final FrameTupleAppender appender;
+    private final ArrayTupleBuilder tupleBuilder;
+
+    private boolean first;
+
+    public ClusteredGroupWriter(IHyracksTaskContext ctx, int[] groupFields, IBinaryComparator[] comparators,
+            IClusteredAggregatorDescriptorFactory aggregatorFactory, RecordDescriptor inRecordDesc,
+            RecordDescriptor outRecordDesc, IFrameWriter writer) throws HyracksDataException {
+        this.groupFields = groupFields;
+        this.comparators = comparators;
+        this.writer = writer;
+        copyFrame = ctx.allocateFrame();
+        inFrameAccessor = new FrameTupleAccessor(ctx.getFrameSize(), inRecordDesc);
+        copyFrameAccessor = new FrameTupleAccessor(ctx.getFrameSize(), inRecordDesc);
+        copyFrameAccessor.reset(copyFrame);
+
+        outFrame = ctx.allocateFrame();
+        appender = new FrameTupleAppender(ctx.getFrameSize());
+        appender.reset(outFrame, true);
+
+        tupleBuilder = new ArrayTupleBuilder(outRecordDesc.getFields().length);
+        this.aggregator = aggregatorFactory.createAggregator(ctx, inRecordDesc, outRecordDesc, groupFields, groupFields, writer, outFrame, appender);
+        this.aggregateState = aggregator.createAggregateStates();
+    }
+
+    @Override
+    public void open() throws HyracksDataException {
+        writer.open();
+        first = true;
+    }
+
+    @Override
+    public void nextFrame(ByteBuffer buffer) throws HyracksDataException {
+        inFrameAccessor.reset(buffer);
+        int nTuples = inFrameAccessor.getTupleCount();
+        for (int i = 0; i < nTuples; ++i) {
+            if (first) {
+
+                tupleBuilder.reset();
+                for (int j = 0; j < groupFields.length; j++) {
+                    tupleBuilder.addField(inFrameAccessor, i, groupFields[j]);
+                }
+                aggregator.init(tupleBuilder, inFrameAccessor, i, aggregateState);
+
+                first = false;
+
+            } else {
+                if (i == 0) {
+                    switchGroupIfRequired(copyFrameAccessor, copyFrameAccessor.getTupleCount() - 1, inFrameAccessor, i);
+                } else {
+                    switchGroupIfRequired(inFrameAccessor, i - 1, inFrameAccessor, i);
+                }
+
+            }
+        }
+        FrameUtils.copy(buffer, copyFrame);
+    }
+
+    private void switchGroupIfRequired(FrameTupleAccessor prevTupleAccessor, int prevTupleIndex,
+            FrameTupleAccessor currTupleAccessor, int currTupleIndex) throws HyracksDataException {
+        if (!sameGroup(prevTupleAccessor, prevTupleIndex, currTupleAccessor, currTupleIndex)) {
+            writeOutput(prevTupleAccessor, prevTupleIndex);
+
+            tupleBuilder.reset();
+            for (int j = 0; j < groupFields.length; j++) {
+                tupleBuilder.addField(currTupleAccessor, currTupleIndex, groupFields[j]);
+            }
+            aggregator.init(tupleBuilder, currTupleAccessor, currTupleIndex, aggregateState);
+        } else {
+            aggregator.aggregate(currTupleAccessor, currTupleIndex, null, 0, aggregateState);
+        }
+    }
+
+    private void writeOutput(final FrameTupleAccessor lastTupleAccessor, int lastTupleIndex)
+            throws HyracksDataException {
+        tupleBuilder.reset();
+        for (int j = 0; j < groupFields.length; j++) {
+            tupleBuilder.addField(lastTupleAccessor, lastTupleIndex, groupFields[j]);
+        }
+        aggregator.outputFinalResult(tupleBuilder, lastTupleAccessor, lastTupleIndex, aggregateState);
+        if (!appender.appendSkipEmptyField(tupleBuilder.getFieldEndOffsets(), tupleBuilder.getByteArray(), 0,
+                tupleBuilder.getSize())) {
+            FrameUtils.flushFrame(outFrame, writer);
+            appender.reset(outFrame, true);
+            if (!appender.appendSkipEmptyField(tupleBuilder.getFieldEndOffsets(), tupleBuilder.getByteArray(), 0,
+                    tupleBuilder.getSize())) {
+                throw new HyracksDataException("The output of size " + tupleBuilder.getSize()
+                        + " cannot be fit into a frame of size " + outFrame.array().length);
+            }
+        }
+
+    }
+
+    private boolean sameGroup(FrameTupleAccessor a1, int t1Idx, FrameTupleAccessor a2, int t2Idx) {
+        for (int i = 0; i < comparators.length; ++i) {
+            int fIdx = groupFields[i];
+            int s1 = a1.getTupleStartOffset(t1Idx) + a1.getFieldSlotsLength() + a1.getFieldStartOffset(t1Idx, fIdx);
+            int l1 = a1.getFieldLength(t1Idx, fIdx);
+            int s2 = a2.getTupleStartOffset(t2Idx) + a2.getFieldSlotsLength() + a2.getFieldStartOffset(t2Idx, fIdx);
+            int l2 = a2.getFieldLength(t2Idx, fIdx);
+            if (comparators[i].compare(a1.getBuffer().array(), s1, l1, a2.getBuffer().array(), s2, l2) != 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    @Override
+    public void fail() throws HyracksDataException {
+        writer.fail();
+    }
+
+    @Override
+    public void close() throws HyracksDataException {
+        if (!first) {
+            writeOutput(copyFrameAccessor, copyFrameAccessor.getTupleCount() - 1);
+            if (appender.getTupleCount() > 0) {
+                FrameUtils.flushFrame(outFrame, writer);
+            }
+        }
+        aggregateState.close();
+        writer.close();
+    }
+}
\ No newline at end of file
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/IClusteredAggregatorDescriptorFactory.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/IClusteredAggregatorDescriptorFactory.java
new file mode 100644
index 0000000..3256f08
--- /dev/null
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/group/IClusteredAggregatorDescriptorFactory.java
@@ -0,0 +1,36 @@
+/*
+ * 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.pregelix.dataflow.group;
+
+import java.io.Serializable;
+import java.nio.ByteBuffer;
+
+import edu.uci.ics.hyracks.api.comm.IFrameWriter;
+import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
+import edu.uci.ics.hyracks.api.dataflow.value.RecordDescriptor;
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
+import edu.uci.ics.hyracks.dataflow.common.comm.io.FrameTupleAppender;
+import edu.uci.ics.hyracks.dataflow.std.group.IAggregatorDescriptor;
+
+/**
+ *
+ */
+public interface IClusteredAggregatorDescriptorFactory extends Serializable {
+
+    IAggregatorDescriptor createAggregator(IHyracksTaskContext ctx, RecordDescriptor inRecordDescriptor,
+            RecordDescriptor outRecordDescriptor, int[] keyFields, final int[] keyFieldsInPartialResults,
+            IFrameWriter resultWriter, ByteBuffer outputFrame, FrameTupleAppender appender) throws HyracksDataException;
+
+}
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 5156dbf..7221cb5 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
@@ -157,16 +157,34 @@
             ITupleReference tupleRef = cursor.getTuple();
 
             /**
+             * merge with updated tuple
+             */
+            ITupleReference indexEntryTuple = tupleRef;
+            ITupleReference cachedUpdatedLastTuple = updateBuffer.getLastTuple();
+            if (cachedUpdatedLastTuple != null) {
+                if (compare(cachedUpdatedLastTuple, tupleRef) == 0) {
+                    indexEntryTuple = cachedUpdatedLastTuple;
+                }
+            }
+
+            /**
              * call the update function
              */
-            functionProxy.functionCall(leftAccessor, tIndex, tupleRef, cloneUpdateTb);
+            functionProxy.functionCall(leftAccessor, tIndex, indexEntryTuple, cloneUpdateTb);
 
-            //doing copy update
-            CopyUpdateUtil.copyUpdate(tempTupleReference, tupleRef, updateBuffer, cloneUpdateTb, indexAccessor, cursor,
-                    rangePred);
+            /**
+             * doing copy update
+             */
+            CopyUpdateUtil.copyUpdate(tempTupleReference, indexEntryTuple, updateBuffer, cloneUpdateTb, indexAccessor,
+                    cursor, rangePred);
         }
     }
 
+    /** compare tuples */
+    private int compare(ITupleReference left, ITupleReference right) throws Exception {
+        return lowKeySearchCmp.compare(left, right);
+    }
+
     @Override
     public void nextFrame(ByteBuffer buffer) throws HyracksDataException {
         accessor.reset(buffer);
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 4ca7533..b21cd2a 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
@@ -195,8 +195,10 @@
                 // TODO: currently use low key only, check what they mean
                 int cmp = compare(lowKey, currentTopTuple);
                 if (cmp <= 0) {
-                    if (cmp == 0)
+                    if (cmp == 0) {
                         outputMatch(i);
+                        currentTopTuple = cursor.getTuple();
+                    }
                     i++;
                 } else {
                     moveTreeCursor();
@@ -262,16 +264,28 @@
     }
 
     //for the join match casesos
-    private void writeResults(IFrameTupleAccessor leftAccessor, int tIndex, ITupleReference frameTuple)
+    private void writeResults(IFrameTupleAccessor leftAccessor, int tIndex, ITupleReference indexTuple)
             throws Exception {
         /**
+         * merge with the cached tuple, if any
+         */
+        ITupleReference indexEntryTuple = indexTuple;
+        ITupleReference cachedUpdatedLastTuple = updateBuffer.getLastTuple();
+        if (cachedUpdatedLastTuple != null) {
+            if (compare(cachedUpdatedLastTuple, indexTuple) == 0) {
+                indexEntryTuple = cachedUpdatedLastTuple;
+            }
+        }
+        /**
          * function call
          */
-        functionProxy.functionCall(leftAccessor, tIndex, frameTuple, cloneUpdateTb);
+        functionProxy.functionCall(leftAccessor, tIndex, indexEntryTuple, cloneUpdateTb);
 
-        //doing clone update
-        CopyUpdateUtil.copyUpdate(tempTupleReference, frameTuple, updateBuffer, cloneUpdateTb, indexAccessor, cursor,
-                rangePred);
+        /**
+         * doing clone update
+         */
+        CopyUpdateUtil.copyUpdate(tempTupleReference, indexEntryTuple, updateBuffer, cloneUpdateTb, indexAccessor,
+                cursor, rangePred);
     }
 
     /** write result for outer case */
@@ -290,4 +304,4 @@
     public void setOutputFrameWriter(int index, IFrameWriter writer, RecordDescriptor recordDesc) {
         writers[index] = writer;
     }
-}
\ No newline at end of file
+}
diff --git a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/util/UpdateBuffer.java b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/util/UpdateBuffer.java
index b2be366..ea1e02e 100644
--- a/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/util/UpdateBuffer.java
+++ b/pregelix/pregelix-dataflow-std/src/main/java/edu/uci/ics/pregelix/dataflow/util/UpdateBuffer.java
@@ -25,6 +25,7 @@
 import edu.uci.ics.hyracks.dataflow.common.comm.io.ArrayTupleBuilder;
 import edu.uci.ics.hyracks.dataflow.common.comm.io.FrameTupleAppender;
 import edu.uci.ics.hyracks.dataflow.common.data.accessors.FrameTupleReference;
+import edu.uci.ics.hyracks.dataflow.common.data.accessors.ITupleReference;
 import edu.uci.ics.hyracks.storage.am.common.api.IIndexAccessor;
 import edu.uci.ics.hyracks.storage.am.common.api.IndexException;
 
@@ -41,6 +42,7 @@
     private final FrameTupleAppender appender;
     private final IHyracksTaskContext ctx;
     private final FrameTupleReference tuple = new FrameTupleReference();
+    private final FrameTupleReference lastTuple = new FrameTupleReference();
     private final int frameSize;
     private IFrameTupleAccessor fta;
 
@@ -104,6 +106,21 @@
         appender.reset(buffer, true);
     }
 
+    /**
+     * return the last updated
+     * 
+     * @throws HyracksDataException
+     */
+    public ITupleReference getLastTuple() throws HyracksDataException {
+        fta.reset(buffers.get(currentInUse));
+        int tupleIndex = fta.getTupleCount() - 1;
+        if (tupleIndex < 0) {
+            return null;
+        }
+        lastTuple.reset(fta, tupleIndex);
+        return lastTuple;
+    }
+
     private void allocate(int index) throws HyracksDataException {
         if (index >= buffers.size()) {
             buffers.add(ctx.allocateFrame());