diff --git a/pregelix/pregelix-core/pom.xml b/pregelix/pregelix-core/pom.xml
index 2a3efcf..a3f24f4 100644
--- a/pregelix/pregelix-core/pom.xml
+++ b/pregelix/pregelix-core/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>
 
 
@@ -209,84 +209,84 @@
 		<dependency>
 			<groupId>edu.uci.ics.hyracks</groupId>
 			<artifactId>pregelix-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>pregelix-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>pregelix-dataflow</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>pregelix-runtime</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-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-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>
@@ -300,7 +300,7 @@
 		<dependency>
 			<groupId>edu.uci.ics.hyracks.examples</groupId>
 			<artifactId>hyracks-integration-tests</artifactId>
-			<version>0.2.7-SNAPSHOT</version>
+			<version>0.2.10-SNAPSHOT</version>
 			<scope>test</scope>
 		</dependency>
 		<dependency>
@@ -320,7 +320,7 @@
 		<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-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java
index db6c2c8..c144ddd 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenInnerJoin.java
@@ -32,8 +32,6 @@
 import edu.uci.ics.hyracks.dataflow.std.connectors.MToNPartitioningMergingConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.connectors.OneToOneConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.file.IFileSplitProvider;
-import edu.uci.ics.hyracks.dataflow.std.group.IAggregatorDescriptorFactory;
-import edu.uci.ics.hyracks.dataflow.std.group.preclustered.PreclusteredGroupOperatorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.sort.ExternalSortOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.TreeIndexInsertUpdateDeleteOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallbackFactory;
@@ -54,6 +52,8 @@
 import edu.uci.ics.pregelix.dataflow.MaterializingWriteOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.TerminationStateWriterOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.base.IConfigurationFactory;
+import edu.uci.ics.pregelix.dataflow.group.ClusteredGroupOperatorDescriptor;
+import edu.uci.ics.pregelix.dataflow.group.IClusteredAggregatorDescriptorFactory;
 import edu.uci.ics.pregelix.dataflow.std.IndexNestedLoopJoinFunctionUpdateOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.std.IndexNestedLoopJoinOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.std.RuntimeHookOperatorDescriptor;
@@ -178,18 +178,18 @@
         /**
          * construct local pre-clustered group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf, false,
-                false);
-        PreclusteredGroupOperatorDescriptor localGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf,
+                false, false);
+        ClusteredGroupOperatorDescriptor localGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactory, rdUnnestedMessage);
         ClusterConfig.setLocationConstraint(spec, localGby);
 
         /**
          * construct global group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(conf,
-                true, true);
-        PreclusteredGroupOperatorDescriptor globalGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(
+                conf, true, true);
+        ClusteredGroupOperatorDescriptor globalGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactoryFinal, rdFinal);
         ClusterConfig.setLocationConstraint(spec, globalGby);
 
@@ -383,18 +383,18 @@
         /**
          * construct local pre-clustered group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf, false,
-                false);
-        PreclusteredGroupOperatorDescriptor localGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf,
+                false, false);
+        ClusteredGroupOperatorDescriptor localGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactory, rdUnnestedMessage);
         ClusterConfig.setLocationConstraint(spec, localGby);
 
         /**
          * construct global group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(conf,
-                true, true);
-        PreclusteredGroupOperatorDescriptor globalGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(
+                conf, true, true);
+        ClusteredGroupOperatorDescriptor globalGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactoryFinal, rdFinal);
         ClusterConfig.setLocationConstraint(spec, globalGby);
 
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java
index 3af8921..c29ea18 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoin.java
@@ -32,8 +32,6 @@
 import edu.uci.ics.hyracks.dataflow.std.connectors.MToNPartitioningMergingConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.connectors.OneToOneConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.file.IFileSplitProvider;
-import edu.uci.ics.hyracks.dataflow.std.group.IAggregatorDescriptorFactory;
-import edu.uci.ics.hyracks.dataflow.std.group.preclustered.PreclusteredGroupOperatorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.sort.ExternalSortOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.TreeIndexInsertUpdateDeleteOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallbackFactory;
@@ -54,6 +52,8 @@
 import edu.uci.ics.pregelix.dataflow.MaterializingWriteOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.TerminationStateWriterOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.base.IConfigurationFactory;
+import edu.uci.ics.pregelix.dataflow.group.ClusteredGroupOperatorDescriptor;
+import edu.uci.ics.pregelix.dataflow.group.IClusteredAggregatorDescriptorFactory;
 import edu.uci.ics.pregelix.dataflow.std.IndexNestedLoopJoinFunctionUpdateOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.std.RuntimeHookOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.std.TreeSearchFunctionUpdateOperatorDescriptor;
@@ -144,9 +144,9 @@
         /**
          * construct local pre-clustered group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf, false,
-                false);
-        PreclusteredGroupOperatorDescriptor localGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf,
+                false, false);
+        ClusteredGroupOperatorDescriptor localGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactory, rdUnnestedMessage);
         ClusterConfig.setLocationConstraint(spec, localGby);
 
@@ -155,9 +155,9 @@
          */
         RecordDescriptor rdFinal = DataflowUtils.getRecordDescriptorFromKeyValueClasses(vertexIdClass.getName(),
                 MsgList.class.getName());
-        IAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(conf,
-                true, true);
-        PreclusteredGroupOperatorDescriptor globalGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(
+                conf, true, true);
+        ClusteredGroupOperatorDescriptor globalGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactoryFinal, rdFinal);
         ClusterConfig.setLocationConstraint(spec, globalGby);
 
@@ -198,8 +198,8 @@
         int[] fieldPermutation = new int[] { 0, 1 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor insertOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdInsert, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(), null,
-                NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(),
+                null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, insertOp);
 
         /**
@@ -208,8 +208,8 @@
         int[] fieldPermutationDelete = new int[] { 0 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor deleteOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdDelete, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE, getIndexDataflowHelperFactory(),
-                null, NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE,
+                getIndexDataflowHelperFactory(), null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, deleteOp);
 
         /** construct empty sink operator */
@@ -323,9 +323,10 @@
 
         IndexNestedLoopJoinFunctionUpdateOperatorDescriptor join = new IndexNestedLoopJoinFunctionUpdateOperatorDescriptor(
                 spec, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits, comparatorFactories,
-                JobGenUtil.getForwardScan(iteration), keyFields, keyFields, true, true, getIndexDataflowHelperFactory(), true,
-                nullWriterFactories, inputRdFactory, 5, new ComputeUpdateFunctionFactory(confFactory), preHookFactory,
-                null, rdUnnestedMessage, rdDummy, rdPartialAggregate, rdInsert, rdDelete);
+                JobGenUtil.getForwardScan(iteration), keyFields, keyFields, true, true,
+                getIndexDataflowHelperFactory(), true, nullWriterFactories, inputRdFactory, 5,
+                new ComputeUpdateFunctionFactory(confFactory), preHookFactory, null, rdUnnestedMessage, rdDummy,
+                rdPartialAggregate, rdInsert, rdDelete);
         ClusterConfig.setLocationConstraint(spec, join);
 
         /**
@@ -342,18 +343,18 @@
         /**
          * construct local pre-clustered group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf, false,
-                false);
-        PreclusteredGroupOperatorDescriptor localGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf,
+                false, false);
+        ClusteredGroupOperatorDescriptor localGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactory, rdUnnestedMessage);
         ClusterConfig.setLocationConstraint(spec, localGby);
 
         /**
          * construct global group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(conf,
-                true, true);
-        PreclusteredGroupOperatorDescriptor globalGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(
+                conf, true, true);
+        ClusteredGroupOperatorDescriptor globalGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactoryFinal, rdFinal);
         ClusterConfig.setLocationConstraint(spec, globalGby);
 
@@ -394,8 +395,8 @@
         int[] fieldPermutation = new int[] { 0, 1 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor insertOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdInsert, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(), null,
-                NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(),
+                null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, insertOp);
 
         /**
@@ -404,8 +405,8 @@
         int[] fieldPermutationDelete = new int[] { 0 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor deleteOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdDelete, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE, getIndexDataflowHelperFactory(),
-                null, NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE,
+                getIndexDataflowHelperFactory(), null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, deleteOp);
 
         /** construct empty sink operator */
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java
index 50949aa..dc61971 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSingleSort.java
@@ -31,8 +31,6 @@
 import edu.uci.ics.hyracks.dataflow.std.connectors.MToNPartitioningConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.connectors.OneToOneConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.file.IFileSplitProvider;
-import edu.uci.ics.hyracks.dataflow.std.group.IAggregatorDescriptorFactory;
-import edu.uci.ics.hyracks.dataflow.std.group.preclustered.PreclusteredGroupOperatorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.sort.ExternalSortOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.TreeIndexInsertUpdateDeleteOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallbackFactory;
@@ -53,6 +51,8 @@
 import edu.uci.ics.pregelix.dataflow.MaterializingWriteOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.TerminationStateWriterOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.base.IConfigurationFactory;
+import edu.uci.ics.pregelix.dataflow.group.ClusteredGroupOperatorDescriptor;
+import edu.uci.ics.pregelix.dataflow.group.IClusteredAggregatorDescriptorFactory;
 import edu.uci.ics.pregelix.dataflow.std.IndexNestedLoopJoinFunctionUpdateOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.std.RuntimeHookOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.std.TreeSearchFunctionUpdateOperatorDescriptor;
@@ -148,9 +148,9 @@
          */
         RecordDescriptor rdFinal = DataflowUtils.getRecordDescriptorFromKeyValueClasses(vertexIdClass.getName(),
                 MsgList.class.getName());
-        IAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(conf,
-                true, false);
-        PreclusteredGroupOperatorDescriptor globalGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(
+                conf, true, false);
+        ClusteredGroupOperatorDescriptor globalGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactoryFinal, rdFinal);
         ClusterConfig.setLocationConstraint(spec, globalGby);
 
@@ -190,8 +190,8 @@
         int[] fieldPermutation = new int[] { 0, 1 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor insertOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdInsert, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(), null,
-                NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(),
+                null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, insertOp);
 
         /**
@@ -200,8 +200,8 @@
         int[] fieldPermutationDelete = new int[] { 0 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor deleteOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdDelete, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE, getIndexDataflowHelperFactory(),
-                null, NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE,
+                getIndexDataflowHelperFactory(), null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, deleteOp);
 
         /** construct empty sink operator */
@@ -312,9 +312,10 @@
 
         IndexNestedLoopJoinFunctionUpdateOperatorDescriptor join = new IndexNestedLoopJoinFunctionUpdateOperatorDescriptor(
                 spec, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits, comparatorFactories,
-                JobGenUtil.getForwardScan(iteration), keyFields, keyFields, true, true, getIndexDataflowHelperFactory(), true,
-                nullWriterFactories, inputRdFactory, 5, new ComputeUpdateFunctionFactory(confFactory), preHookFactory,
-                null, rdUnnestedMessage, rdDummy, rdPartialAggregate, rdInsert, rdDelete);
+                JobGenUtil.getForwardScan(iteration), keyFields, keyFields, true, true,
+                getIndexDataflowHelperFactory(), true, nullWriterFactories, inputRdFactory, 5,
+                new ComputeUpdateFunctionFactory(confFactory), preHookFactory, null, rdUnnestedMessage, rdDummy,
+                rdPartialAggregate, rdInsert, rdDelete);
         ClusterConfig.setLocationConstraint(spec, join);
 
         /**
@@ -331,9 +332,9 @@
         /**
          * construct global group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(conf,
-                true, false);
-        PreclusteredGroupOperatorDescriptor globalGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(
+                conf, true, false);
+        ClusteredGroupOperatorDescriptor globalGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactoryFinal, rdFinal);
         ClusterConfig.setLocationConstraint(spec, globalGby);
 
@@ -371,8 +372,8 @@
         int[] fieldPermutation = new int[] { 0, 1 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor insertOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdInsert, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(), null,
-                NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(),
+                null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, insertOp);
 
         /**
@@ -381,8 +382,8 @@
         int[] fieldPermutationDelete = new int[] { 0 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor deleteOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdDelete, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE, getIndexDataflowHelperFactory(),
-                null, NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE,
+                getIndexDataflowHelperFactory(), null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, deleteOp);
 
         /** construct empty sink operator */
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java
index 362e413..34f723f 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/jobgen/JobGenOuterJoinSort.java
@@ -31,8 +31,6 @@
 import edu.uci.ics.hyracks.dataflow.std.connectors.MToNPartitioningConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.connectors.OneToOneConnectorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.file.IFileSplitProvider;
-import edu.uci.ics.hyracks.dataflow.std.group.IAggregatorDescriptorFactory;
-import edu.uci.ics.hyracks.dataflow.std.group.preclustered.PreclusteredGroupOperatorDescriptor;
 import edu.uci.ics.hyracks.dataflow.std.sort.ExternalSortOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.TreeIndexInsertUpdateDeleteOperatorDescriptor;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallbackFactory;
@@ -53,6 +51,8 @@
 import edu.uci.ics.pregelix.dataflow.MaterializingWriteOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.TerminationStateWriterOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.base.IConfigurationFactory;
+import edu.uci.ics.pregelix.dataflow.group.ClusteredGroupOperatorDescriptor;
+import edu.uci.ics.pregelix.dataflow.group.IClusteredAggregatorDescriptorFactory;
 import edu.uci.ics.pregelix.dataflow.std.IndexNestedLoopJoinFunctionUpdateOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.std.RuntimeHookOperatorDescriptor;
 import edu.uci.ics.pregelix.dataflow.std.TreeSearchFunctionUpdateOperatorDescriptor;
@@ -143,9 +143,9 @@
         /**
          * construct local pre-clustered group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf, false,
-                false);
-        PreclusteredGroupOperatorDescriptor localGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf,
+                false, false);
+        ClusteredGroupOperatorDescriptor localGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactory, rdUnnestedMessage);
         ClusterConfig.setLocationConstraint(spec, localGby);
 
@@ -161,9 +161,9 @@
          */
         RecordDescriptor rdFinal = DataflowUtils.getRecordDescriptorFromKeyValueClasses(vertexIdClass.getName(),
                 MsgList.class.getName());
-        IAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(conf,
-                true, true);
-        PreclusteredGroupOperatorDescriptor globalGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(
+                conf, true, true);
+        ClusteredGroupOperatorDescriptor globalGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactoryFinal, rdFinal);
         ClusterConfig.setLocationConstraint(spec, globalGby);
 
@@ -204,8 +204,8 @@
         int[] fieldPermutation = new int[] { 0, 1 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor insertOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdInsert, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(), null,
-                NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(),
+                null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, insertOp);
 
         /**
@@ -214,8 +214,8 @@
         int[] fieldPermutationDelete = new int[] { 0 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor deleteOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdDelete, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE, getIndexDataflowHelperFactory(),
-                null, NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE,
+                getIndexDataflowHelperFactory(), null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, deleteOp);
 
         /** construct empty sink operator */
@@ -326,9 +326,10 @@
 
         IndexNestedLoopJoinFunctionUpdateOperatorDescriptor join = new IndexNestedLoopJoinFunctionUpdateOperatorDescriptor(
                 spec, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits, comparatorFactories,
-                JobGenUtil.getForwardScan(iteration), keyFields, keyFields, true, true, getIndexDataflowHelperFactory(), true,
-                nullWriterFactories, inputRdFactory, 5, new ComputeUpdateFunctionFactory(confFactory), preHookFactory,
-                null, rdUnnestedMessage, rdDummy, rdPartialAggregate, rdInsert, rdDelete);
+                JobGenUtil.getForwardScan(iteration), keyFields, keyFields, true, true,
+                getIndexDataflowHelperFactory(), true, nullWriterFactories, inputRdFactory, 5,
+                new ComputeUpdateFunctionFactory(confFactory), preHookFactory, null, rdUnnestedMessage, rdDummy,
+                rdPartialAggregate, rdInsert, rdDelete);
         ClusterConfig.setLocationConstraint(spec, join);
 
         /**
@@ -345,9 +346,9 @@
         /**
          * construct local pre-clustered group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf, false,
-                false);
-        PreclusteredGroupOperatorDescriptor localGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactory = DataflowUtils.getAccumulatingAggregatorFactory(conf,
+                false, false);
+        ClusteredGroupOperatorDescriptor localGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactory, rdUnnestedMessage);
         ClusterConfig.setLocationConstraint(spec, localGby);
 
@@ -361,9 +362,9 @@
         /**
          * construct global group-by operator
          */
-        IAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(conf,
-                true, true);
-        PreclusteredGroupOperatorDescriptor globalGby = new PreclusteredGroupOperatorDescriptor(spec, keyFields,
+        IClusteredAggregatorDescriptorFactory aggregatorFactoryFinal = DataflowUtils.getAccumulatingAggregatorFactory(
+                conf, true, true);
+        ClusteredGroupOperatorDescriptor globalGby = new ClusteredGroupOperatorDescriptor(spec, keyFields,
                 sortCmpFactories, aggregatorFactoryFinal, rdFinal);
         ClusterConfig.setLocationConstraint(spec, globalGby);
 
@@ -404,8 +405,8 @@
         int[] fieldPermutation = new int[] { 0, 1 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor insertOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdInsert, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(), null,
-                NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutation, IndexOperation.INSERT, getIndexDataflowHelperFactory(),
+                null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, insertOp);
 
         /**
@@ -414,8 +415,8 @@
         int[] fieldPermutationDelete = new int[] { 0 };
         TreeIndexInsertUpdateDeleteOperatorDescriptor deleteOp = new TreeIndexInsertUpdateDeleteOperatorDescriptor(
                 spec, rdDelete, storageManagerInterface, lcManagerProvider, fileSplitProvider, typeTraits,
-                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE, getIndexDataflowHelperFactory(),
-                null, NoOpOperationCallbackFactory.INSTANCE);
+                comparatorFactories, null, fieldPermutationDelete, IndexOperation.DELETE,
+                getIndexDataflowHelperFactory(), null, NoOpOperationCallbackFactory.INSTANCE);
         ClusterConfig.setLocationConstraint(spec, deleteOp);
 
         /** construct empty sink operator */
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/util/DataflowUtils.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/util/DataflowUtils.java
index 0876893..3e01109 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/util/DataflowUtils.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/util/DataflowUtils.java
@@ -21,9 +21,9 @@
 import edu.uci.ics.hyracks.api.dataflow.value.ISerializerDeserializer;
 import edu.uci.ics.hyracks.api.dataflow.value.RecordDescriptor;
 import edu.uci.ics.hyracks.api.exceptions.HyracksException;
-import edu.uci.ics.hyracks.dataflow.std.group.IAggregatorDescriptorFactory;
 import edu.uci.ics.pregelix.core.hadoop.config.ConfigurationFactory;
 import edu.uci.ics.pregelix.core.runtime.touchpoint.WritableRecordDescriptorFactory;
+import edu.uci.ics.pregelix.dataflow.group.IClusteredAggregatorDescriptorFactory;
 import edu.uci.ics.pregelix.dataflow.std.base.IAggregateFunctionFactory;
 import edu.uci.ics.pregelix.dataflow.std.base.IRecordDescriptorFactory;
 import edu.uci.ics.pregelix.runtime.simpleagg.AccumulatingAggregatorFactory;
@@ -75,11 +75,11 @@
         return rdFactory;
     }
 
-    public static IAggregatorDescriptorFactory getAccumulatingAggregatorFactory(Configuration conf, boolean isFinal,
-            boolean partialAggAsInput) {
+    public static IClusteredAggregatorDescriptorFactory getAccumulatingAggregatorFactory(Configuration conf,
+            boolean isFinal, boolean partialAggAsInput) {
         IAggregateFunctionFactory aggFuncFactory = new AggregationFunctionFactory(new ConfigurationFactory(conf),
                 isFinal, partialAggAsInput);
-        IAggregatorDescriptorFactory aggregatorFactory = new AccumulatingAggregatorFactory(
+        IClusteredAggregatorDescriptorFactory aggregatorFactory = new AccumulatingAggregatorFactory(
                 new IAggregateFunctionFactory[] { aggFuncFactory });
         return aggregatorFactory;
     }
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/util/PregelixHyracksIntegrationUtil.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/util/PregelixHyracksIntegrationUtil.java
index 73b053f..e8a6b5c 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/util/PregelixHyracksIntegrationUtil.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/util/PregelixHyracksIntegrationUtil.java
@@ -14,8 +14,11 @@
  */
 package edu.uci.ics.pregelix.core.util;
 
+import java.io.File;
 import java.util.EnumSet;
 
+import org.apache.commons.io.FileUtils;
+
 import edu.uci.ics.hyracks.api.client.HyracksConnection;
 import edu.uci.ics.hyracks.api.client.IHyracksClientConnection;
 import edu.uci.ics.hyracks.api.job.JobFlag;
@@ -46,6 +49,10 @@
     private static IHyracksClientConnection hcc;
 
     public static void init() throws Exception {
+        FileUtils.forceMkdir(new File("dev1"));
+        FileUtils.forceMkdir(new File("dev2"));
+        FileUtils.forceMkdir(new File("dev3"));
+        FileUtils.forceMkdir(new File("dev4"));
         CCConfig ccConfig = new CCConfig();
         ccConfig.clientNetIpAddress = CC_HOST;
         ccConfig.clusterNetIpAddress = CC_HOST;
@@ -80,7 +87,7 @@
         ncConfig2.datasetIPAddress = "127.0.0.1";
         ncConfig2.nodeId = NC2_ID;
         ncConfig2.appNCMainClass = NCApplicationEntryPoint.class.getName();
-        ncConfig2.ioDevices="dev1,dev2";
+        ncConfig2.ioDevices="dev3,dev4";
         nc2 = new NodeControllerService(ncConfig2);
         nc2.start();