diff --git a/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/base/RuleCollections.java b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/base/RuleCollections.java
index a05ed27..d4ff954 100644
--- a/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/base/RuleCollections.java
+++ b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/base/RuleCollections.java
@@ -19,6 +19,7 @@
 import java.util.List;
 
 import edu.uci.ics.asterix.optimizer.rules.AsterixInlineVariablesRule;
+import edu.uci.ics.asterix.optimizer.rules.AsterixIntroduceGroupByCombinerRule;
 import edu.uci.ics.asterix.optimizer.rules.ByNameToByIndexFieldAccessRule;
 import edu.uci.ics.asterix.optimizer.rules.CancelUnnestWithNestedListifyRule;
 import edu.uci.ics.asterix.optimizer.rules.CheckFilterExpressionTypeRule;
@@ -85,7 +86,6 @@
 import edu.uci.ics.hyracks.algebricks.rewriter.rules.IntroHashPartitionMergeExchange;
 import edu.uci.ics.hyracks.algebricks.rewriter.rules.IntroJoinInsideSubplanRule;
 import edu.uci.ics.hyracks.algebricks.rewriter.rules.IntroduceAggregateCombinerRule;
-import edu.uci.ics.hyracks.algebricks.rewriter.rules.IntroduceGroupByCombinerRule;
 import edu.uci.ics.hyracks.algebricks.rewriter.rules.IntroduceGroupByForSubplanRule;
 import edu.uci.ics.hyracks.algebricks.rewriter.rules.IntroduceProjectsRule;
 import edu.uci.ics.hyracks.algebricks.rewriter.rules.IsolateHyracksOperatorsRule;
@@ -214,7 +214,7 @@
         consolidation.add(new ConsolidateSelectsRule());
         consolidation.add(new ConsolidateAssignsRule());
         consolidation.add(new InlineAssignIntoAggregateRule());
-        consolidation.add(new IntroduceGroupByCombinerRule());
+        consolidation.add(new AsterixIntroduceGroupByCombinerRule());
         consolidation.add(new IntroduceAggregateCombinerRule());
         consolidation.add(new CountVarToCountOneRule());
         consolidation.add(new RemoveUnusedAssignAndAggregateRule());
diff --git a/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/AsterixIntroduceGroupByCombinerRule.java b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/AsterixIntroduceGroupByCombinerRule.java
new file mode 100644
index 0000000..b71ffab
--- /dev/null
+++ b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/AsterixIntroduceGroupByCombinerRule.java
@@ -0,0 +1,74 @@
+/*
+ * 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.asterix.optimizer.rules;
+
+import java.util.ArrayList;
+import java.util.List;
+
+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.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.LogicalVariable;
+import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.ScalarFunctionCallExpression;
+import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.VariableReferenceExpression;
+import edu.uci.ics.hyracks.algebricks.core.algebra.functions.AlgebricksBuiltinFunctions;
+import edu.uci.ics.hyracks.algebricks.core.algebra.functions.IFunctionInfo;
+import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.GroupByOperator;
+import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.SelectOperator;
+import edu.uci.ics.hyracks.algebricks.rewriter.rules.AbstractIntroduceGroupByCombinerRule;
+
+public class AsterixIntroduceGroupByCombinerRule extends AbstractIntroduceGroupByCombinerRule {
+
+    @SuppressWarnings("unchecked")
+    @Override
+    protected void processNullTest(IOptimizationContext context, GroupByOperator nestedGby,
+            List<LogicalVariable> aggregateVarsProducedByCombiner) {
+        IFunctionInfo finfoEq = context.getMetadataProvider().lookupFunction(AsterixBuiltinFunctions.IS_SYSTEM_NULL);
+        SelectOperator selectNonSystemNull;
+
+        if (aggregateVarsProducedByCombiner.size() == 1) {
+            ILogicalExpression isSystemNullTest = new ScalarFunctionCallExpression(finfoEq,
+                    new MutableObject<ILogicalExpression>(new VariableReferenceExpression(
+                            aggregateVarsProducedByCombiner.get(0))));
+            IFunctionInfo finfoNot = context.getMetadataProvider().lookupFunction(AlgebricksBuiltinFunctions.NOT);
+            ScalarFunctionCallExpression nonSystemNullTest = new ScalarFunctionCallExpression(finfoNot,
+                    new MutableObject<ILogicalExpression>(isSystemNullTest));
+            selectNonSystemNull = new SelectOperator(new MutableObject<ILogicalExpression>(nonSystemNullTest), false,
+                    null);
+        } else {
+            List<Mutable<ILogicalExpression>> isSystemNullTestList = new ArrayList<Mutable<ILogicalExpression>>();
+            for (LogicalVariable aggVar : aggregateVarsProducedByCombiner) {
+                ILogicalExpression isSystemNullTest = new ScalarFunctionCallExpression(finfoEq,
+                        new MutableObject<ILogicalExpression>(new VariableReferenceExpression(aggVar)));
+                IFunctionInfo finfoNot = context.getMetadataProvider().lookupFunction(AlgebricksBuiltinFunctions.NOT);
+                ScalarFunctionCallExpression nonSystemNullTest = new ScalarFunctionCallExpression(finfoNot,
+                        new MutableObject<ILogicalExpression>(isSystemNullTest));
+                isSystemNullTestList.add(new MutableObject<ILogicalExpression>(nonSystemNullTest));
+            }
+            IFunctionInfo finfoAnd = context.getMetadataProvider().lookupFunction(AlgebricksBuiltinFunctions.AND);
+            selectNonSystemNull = new SelectOperator(new MutableObject<ILogicalExpression>(
+                    new ScalarFunctionCallExpression(finfoAnd, isSystemNullTestList)), false, null);
+        }
+
+        //add the not-system-null check into the nested pipeline
+        Mutable<ILogicalOperator> ntsBeforeNestedGby = nestedGby.getInputs().get(0);
+        nestedGby.getInputs().set(0, new MutableObject<ILogicalOperator>(selectNonSystemNull));
+        selectNonSystemNull.getInputs().add(ntsBeforeNestedGby);
+    }
+}
diff --git a/asterix-app/data/tpch0.001/selectednation.tbl b/asterix-app/data/tpch0.001/selectednation.tbl
new file mode 100644
index 0000000..740375c
--- /dev/null
+++ b/asterix-app/data/tpch0.001/selectednation.tbl
@@ -0,0 +1,11 @@
+0|ALGERIA|0| haggle. carefully final deposits detect slyly agai|
+1|ARGENTINA|1|al foxes promise slyly according to the regular accounts. bold requests alon|
+2|BRAZIL|1|y alongside of the pending deposits. carefully special packages are about the ironic forges. slyly special |
+3|CANADA|1|eas hang ironic, silent packages. slyly regular packages are furiously over the tithes. fluffily bold|
+4|EGYPT|4|y above the carefully unusual theodolites. final dugouts are quickly across the furiously regular d|
+19|ROMANIA|3|ular asymptotes are about the furious multipliers. express dependencies nag above the ironically ironic account|
+20|SAUDI ARABIA|4|ts. silent requests haggle. closely express packages sleep across the blithely|
+21|VIETNAM|2|hely enticingly express accounts. even, final |
+22|RUSSIA|3| requests against the platelets use never according to the quickly regular pint|
+23|UNITED KINGDOM|3|eans boost carefully special requests. accounts are. carefull|
+24|UNITED STATES|1|y final packages. slow foxes cajole quickly. quickly silent platelets breach ironic accounts. unusual pinto be|
diff --git a/asterix-app/src/test/resources/optimizerts/queries/nest_aggregate.aql b/asterix-app/src/test/resources/optimizerts/queries/nest_aggregate.aql
new file mode 100644
index 0000000..16fc8e4
--- /dev/null
+++ b/asterix-app/src/test/resources/optimizerts/queries/nest_aggregate.aql
@@ -0,0 +1,116 @@
+/*
+ * Description  : This test case is to verify the fix for issue782
+ * https://code.google.com/p/asterixdb/issues/detail?id=782
+ * Expected Res : SUCCESS
+ * Date         : 2nd Jun 2014
+ */
+
+drop dataverse tpch if exists;
+create dataverse tpch;
+
+use dataverse tpch;
+
+create type OrderType as closed {
+  o_orderkey: int32,
+  o_custkey: int32,
+  o_orderstatus: string,
+  o_totalprice: double,
+  o_orderdate: string,
+  o_orderpriority: string,
+  o_clerk: string,
+  o_shippriority: int32,
+  o_comment: string
+}
+
+create type CustomerType as closed {
+  c_custkey: int32,
+  c_name: string,
+  c_address: string,
+  c_nationkey: int32,
+  c_phone: string,
+  c_acctbal: double,
+  c_mktsegment: string,
+  c_comment: string
+}
+
+create type SupplierType as closed {
+  s_suppkey: int32,
+  s_name: string,
+  s_address: string,
+  s_nationkey: int32,
+  s_phone: string,
+  s_acctbal: double,
+  s_comment: string
+}
+
+create type NationType as closed {
+  n_nationkey: int32,
+  n_name: string,
+  n_regionkey: int32,
+  n_comment: string
+}
+
+create type RegionType as closed {
+  r_regionkey: int32,
+  r_name: string,
+  r_comment: string
+}
+
+create type PartType as closed {
+  p_partkey: int32,
+  p_name: string,
+  p_mfgr: string,
+  p_brand: string,
+  p_type: string,
+  p_size: int32,
+  p_container: string,
+  p_retailprice: double,
+  p_comment: string
+}
+
+create type PartSuppType as closed {
+  ps_partkey: int32,
+  ps_suppkey: int32,
+  ps_availqty: int32,
+  ps_supplycost: double,
+  ps_comment: string
+}
+
+create dataset Orders(OrderType)
+  primary key o_orderkey;
+create dataset Supplier(SupplierType)
+  primary key s_suppkey;
+create dataset Region(RegionType)
+  primary key r_regionkey;
+create dataset Nation(NationType)
+  primary key n_nationkey;
+create dataset Part(PartType)
+  primary key p_partkey;
+create dataset Partsupp(PartSuppType)
+  primary key ps_partkey, ps_suppkey;
+create dataset Customer(CustomerType)
+  primary key c_custkey;
+create dataset SelectedNation(NationType)
+  primary key n_nationkey;
+
+
+
+for $nation in dataset Nation
+for $sn in dataset SelectedNation
+where $nation.n_nationkey = $sn.n_nationkey  /*+ indexnl */
+return {
+  "nation_key": $nation.n_nationkey,
+  "name": $nation.n_name,
+  "aggregates": for $order in dataset Orders
+                for $customer in dataset Customer
+                where $order.o_custkey = $customer.c_custkey
+                and  $customer.c_nationkey = $nation.n_nationkey
+                group by $orderdate := $order.o_orderdate with $order
+                let $sum := sum(for $o in $order return $o.o_totalprice)
+                order by $sum
+                limit 3
+                return {
+                  "order_date": $orderdate,
+                  "sum_price": $sum
+                }
+}
\ No newline at end of file
diff --git a/asterix-app/src/test/resources/optimizerts/results/nest_aggregate.plan b/asterix-app/src/test/resources/optimizerts/results/nest_aggregate.plan
new file mode 100644
index 0000000..f3c1040
--- /dev/null
+++ b/asterix-app/src/test/resources/optimizerts/results/nest_aggregate.plan
@@ -0,0 +1,68 @@
+-- DISTRIBUTE_RESULT  |PARTITIONED|
+  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+    -- STREAM_PROJECT  |PARTITIONED|
+      -- ASSIGN  |PARTITIONED|
+        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+          -- PRE_CLUSTERED_GROUP_BY[$$49]  |PARTITIONED|
+                  {
+                    -- AGGREGATE  |LOCAL|
+                      -- STREAM_LIMIT  |LOCAL|
+                        -- IN_MEMORY_STABLE_SORT [$$43(ASC)]  |LOCAL|
+                          -- MICRO_PRE_CLUSTERED_GROUP_BY[$$50]  |LOCAL|
+                                  {
+                                    -- AGGREGATE  |LOCAL|
+                                      -- NESTED_TUPLE_SOURCE  |LOCAL|
+                                  }
+                            -- STREAM_SELECT  |LOCAL|
+                              -- NESTED_TUPLE_SOURCE  |LOCAL|
+                  }
+            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$49(ASC), $$50(ASC)] HASH:[$$49]  |PARTITIONED|
+              -- PRE_CLUSTERED_GROUP_BY[$$39, $$32]  |PARTITIONED|
+                      {
+                        -- AGGREGATE  |LOCAL|
+                          -- STREAM_SELECT  |LOCAL|
+                            -- NESTED_TUPLE_SOURCE  |LOCAL|
+                      }
+                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                  -- STABLE_SORT [$$39(ASC), $$32(ASC)]  |PARTITIONED|
+                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                      -- STREAM_PROJECT  |PARTITIONED|
+                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                          -- HYBRID_HASH_JOIN [$$39][$$41]  |PARTITIONED|
+                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                              -- STREAM_PROJECT  |PARTITIONED|
+                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                  -- HYBRID_HASH_JOIN [$$39][$$35]  |PARTITIONED|
+                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                      -- STREAM_PROJECT  |PARTITIONED|
+                                        -- ASSIGN  |PARTITIONED|
+                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                            -- DATASOURCE_SCAN  |PARTITIONED|
+                                              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                      -- STREAM_PROJECT  |PARTITIONED|
+                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                          -- DATASOURCE_SCAN  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                            -- HASH_PARTITION_EXCHANGE [$$41]  |PARTITIONED|
+                              -- ASSIGN  |PARTITIONED|
+                                -- STREAM_PROJECT  |PARTITIONED|
+                                  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                    -- HYBRID_HASH_JOIN [$$44][$$37]  |PARTITIONED|
+                                      -- HASH_PARTITION_EXCHANGE [$$44]  |PARTITIONED|
+                                        -- STREAM_PROJECT  |PARTITIONED|
+                                          -- ASSIGN  |PARTITIONED|
+                                            -- STREAM_PROJECT  |PARTITIONED|
+                                              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                -- DATASOURCE_SCAN  |PARTITIONED|
+                                                  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                        -- STREAM_PROJECT  |PARTITIONED|
+                                          -- ASSIGN  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- DATASOURCE_SCAN  |PARTITIONED|
+                                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                  -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterix-app/src/test/resources/optimizerts/results/q09_group_by.plan b/asterix-app/src/test/resources/optimizerts/results/q09_group_by.plan
index 8e69282..fc2abd2 100644
--- a/asterix-app/src/test/resources/optimizerts/results/q09_group_by.plan
+++ b/asterix-app/src/test/resources/optimizerts/results/q09_group_by.plan
@@ -4,7 +4,7 @@
       -- ASSIGN  |PARTITIONED|
         -- STREAM_PROJECT  |PARTITIONED|
           -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-            -- HYBRID_HASH_JOIN [$$62][$$85]  |PARTITIONED|
+            -- HYBRID_HASH_JOIN [$$62][$$84]  |PARTITIONED|
               -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                 -- STREAM_PROJECT  |PARTITIONED|
                   -- STREAM_SELECT  |PARTITIONED|
@@ -12,10 +12,10 @@
                       -- DATASOURCE_SCAN  |PARTITIONED|
                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                           -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
-              -- HASH_PARTITION_EXCHANGE [$$85]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$84]  |PARTITIONED|
                 -- STREAM_PROJECT  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- HYBRID_HASH_JOIN [$$64, $$63][$$69, $$85]  |PARTITIONED|
+                    -- HYBRID_HASH_JOIN [$$64, $$63][$$69, $$84]  |PARTITIONED|
                       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                         -- STREAM_PROJECT  |PARTITIONED|
                           -- ASSIGN  |PARTITIONED|
@@ -23,15 +23,15 @@
                               -- DATASOURCE_SCAN  |PARTITIONED|
                                 -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                                   -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
-                      -- HASH_PARTITION_EXCHANGE [$$85, $$69]  |PARTITIONED|
+                      -- HASH_PARTITION_EXCHANGE [$$84, $$69]  |PARTITIONED|
                         -- STREAM_PROJECT  |PARTITIONED|
                           -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                             -- HYBRID_HASH_JOIN [$$65][$$69]  |PARTITIONED|
                               -- HASH_PARTITION_EXCHANGE [$$65]  |PARTITIONED|
                                 -- STREAM_PROJECT  |PARTITIONED|
                                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                    -- HYBRID_HASH_JOIN [$$72][$$66]  |PARTITIONED|
-                                      -- HASH_PARTITION_EXCHANGE [$$72]  |PARTITIONED|
+                                    -- HYBRID_HASH_JOIN [$$77][$$66]  |PARTITIONED|
+                                      -- HASH_PARTITION_EXCHANGE [$$77]  |PARTITIONED|
                                         -- STREAM_PROJECT  |PARTITIONED|
                                           -- ASSIGN  |PARTITIONED|
                                             -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
diff --git a/asterix-app/src/test/resources/runtimets/queries/tpch/nest_aggregate/nest_aggregate.1.ddl.aql b/asterix-app/src/test/resources/runtimets/queries/tpch/nest_aggregate/nest_aggregate.1.ddl.aql
new file mode 100644
index 0000000..72bca42
--- /dev/null
+++ b/asterix-app/src/test/resources/runtimets/queries/tpch/nest_aggregate/nest_aggregate.1.ddl.aql
@@ -0,0 +1,70 @@
+/*
+ * Description  : This test case is to verify the fix for issue782
+ * https://code.google.com/p/asterixdb/issues/detail?id=782
+ * Expected Res : SUCCESS
+ * Date         : 2nd Jun 2014
+ */
+
+drop dataverse tpch if exists;
+create dataverse tpch;
+
+use dataverse tpch;
+
+create type OrderType as closed {
+  o_orderkey: int32,
+  o_custkey: int32,
+  o_orderstatus: string,
+  o_totalprice: double,
+  o_orderdate: string,
+  o_orderpriority: string,
+  o_clerk: string,
+  o_shippriority: int32,
+  o_comment: string
+}
+
+create type CustomerType as closed {
+  c_custkey: int32,
+  c_name: string,
+  c_address: string,
+  c_nationkey: int32,
+  c_phone: string,
+  c_acctbal: double,
+  c_mktsegment: string,
+  c_comment: string
+}
+
+create type SupplierType as closed {
+  s_suppkey: int32,
+  s_name: string,
+  s_address: string,
+  s_nationkey: int32,
+  s_phone: string,
+  s_acctbal: double,
+  s_comment: string
+}
+
+create type NationType as closed {
+  n_nationkey: int32,
+  n_name: string,
+  n_regionkey: int32,
+  n_comment: string
+}
+
+create type RegionType as closed {
+  r_regionkey: int32,
+  r_name: string,
+  r_comment: string
+}
+
+create dataset Orders(OrderType)
+  primary key o_orderkey;
+create dataset Supplier(SupplierType)
+  primary key s_suppkey;
+create dataset Region(RegionType)
+  primary key r_regionkey;
+create dataset Nation(NationType)
+  primary key n_nationkey;
+create dataset Customer(CustomerType)
+  primary key c_custkey;
+create dataset SelectedNation(NationType)
+  primary key n_nationkey;
diff --git a/asterix-app/src/test/resources/runtimets/queries/tpch/nest_aggregate/nest_aggregate.2.update.aql b/asterix-app/src/test/resources/runtimets/queries/tpch/nest_aggregate/nest_aggregate.2.update.aql
new file mode 100644
index 0000000..f1b2dd4
--- /dev/null
+++ b/asterix-app/src/test/resources/runtimets/queries/tpch/nest_aggregate/nest_aggregate.2.update.aql
@@ -0,0 +1,32 @@
+/*
+ * Description  : This test case is to verify the fix for issue782
+ * https://code.google.com/p/asterixdb/issues/detail?id=782
+ * Expected Res : SUCCESS
+ * Date         : 2nd Jun 2014
+ */
+
+use dataverse tpch;
+
+load dataset Orders
+using "edu.uci.ics.asterix.external.dataset.adapter.NCFileSystemAdapter"
+(("path"="nc1://data/tpch0.001/orders.tbl"),("format"="delimited-text"),("delimiter"="|"));
+
+load dataset Supplier
+using "edu.uci.ics.asterix.external.dataset.adapter.NCFileSystemAdapter"
+(("path"="nc1://data/tpch0.001/supplier.tbl"),("format"="delimited-text"),("delimiter"="|"));
+
+load dataset Region
+using "edu.uci.ics.asterix.external.dataset.adapter.NCFileSystemAdapter"
+(("path"="nc1://data/tpch0.001/region.tbl"),("format"="delimited-text"),("delimiter"="|"));
+
+load dataset Nation
+using "edu.uci.ics.asterix.external.dataset.adapter.NCFileSystemAdapter"
+(("path"="nc1://data/tpch0.001/nation.tbl"),("format"="delimited-text"),("delimiter"="|"));
+
+load dataset Customer
+using "edu.uci.ics.asterix.external.dataset.adapter.NCFileSystemAdapter"
+(("path"="nc1://data/tpch0.001/customer.tbl"),("format"="delimited-text"),("delimiter"="|"));
+
+load dataset SelectedNation
+using "edu.uci.ics.asterix.external.dataset.adapter.NCFileSystemAdapter"
+(("path"="nc1://data/tpch0.001/selectednation.tbl"),("format"="delimited-text"),("delimiter"="|"));
diff --git a/asterix-app/src/test/resources/runtimets/queries/tpch/nest_aggregate/nest_aggregate.3.query.aql b/asterix-app/src/test/resources/runtimets/queries/tpch/nest_aggregate/nest_aggregate.3.query.aql
new file mode 100644
index 0000000..5321522
--- /dev/null
+++ b/asterix-app/src/test/resources/runtimets/queries/tpch/nest_aggregate/nest_aggregate.3.query.aql
@@ -0,0 +1,29 @@
+/*
+ * Description  : This test case is to verify the fix for issue782
+ * https://code.google.com/p/asterixdb/issues/detail?id=782
+ * Expected Res : SUCCESS
+ * Date         : 2nd Jun 2014
+ */
+
+use dataverse tpch;
+
+for $nation in dataset Nation
+for $sn in dataset SelectedNation
+where $nation.n_nationkey = $sn.n_nationkey  /*+ indexnl */
+return {
+  "nation_key": $nation.n_nationkey,
+  "name": $nation.n_name,
+  "aggregates":
+                for $order in dataset Orders
+                for $customer in dataset Customer
+                where $order.o_custkey = $customer.c_custkey
+                and  $customer.c_nationkey = $nation.n_nationkey
+                group by $orderdate := $order.o_orderdate with $order
+                let $sum := sum(for $o in $order return $o.o_totalprice)
+                order by $sum
+                limit 3
+                return {
+                      "order_date": $orderdate,
+                      "sum_price": $sum
+                }
+}
\ No newline at end of file
diff --git a/asterix-app/src/test/resources/runtimets/results/tpch/nest_aggregate/nest_aggregate.1.adm b/asterix-app/src/test/resources/runtimets/results/tpch/nest_aggregate/nest_aggregate.1.adm
new file mode 100644
index 0000000..f63ed7e
--- /dev/null
+++ b/asterix-app/src/test/resources/runtimets/results/tpch/nest_aggregate/nest_aggregate.1.adm
@@ -0,0 +1,11 @@
+{ "nation_key": 1, "name": "ARGENTINA", "aggregates": [ { "order_date": "1997-08-14", "sum_price": 16763.95d }, { "order_date": "1997-11-26", "sum_price": 18653.09d }, { "order_date": "1998-04-20", "sum_price": 24637.96d } ] }
+{ "nation_key": 2, "name": "BRAZIL", "aggregates": [  ] }
+{ "nation_key": 19, "name": "ROMANIA", "aggregates": [  ] }
+{ "nation_key": 21, "name": "VIETNAM", "aggregates": [  ] }
+{ "nation_key": 3, "name": "CANADA", "aggregates": [ { "order_date": "1992-02-22", "sum_price": 1084.38d }, { "order_date": "1992-11-28", "sum_price": 4766.19d }, { "order_date": "1995-02-17", "sum_price": 4913.06d } ] }
+{ "nation_key": 23, "name": "UNITED KINGDOM", "aggregates": [  ] }
+{ "nation_key": 4, "name": "EGYPT", "aggregates": [ { "order_date": "1998-04-19", "sum_price": 3089.42d }, { "order_date": "1996-03-12", "sum_price": 3892.77d }, { "order_date": "1997-07-25", "sum_price": 11405.4d } ] }
+{ "nation_key": 22, "name": "RUSSIA", "aggregates": [  ] }
+{ "nation_key": 24, "name": "UNITED STATES", "aggregates": [  ] }
+{ "nation_key": 0, "name": "ALGERIA", "aggregates": [ { "order_date": "1994-05-27", "sum_price": 1051.15d }, { "order_date": "1994-05-08", "sum_price": 4819.91d }, { "order_date": "1993-08-27", "sum_price": 10500.27d } ] }
+{ "nation_key": 20, "name": "SAUDI ARABIA", "aggregates": [  ] }
diff --git a/asterix-app/src/test/resources/runtimets/testsuite.xml b/asterix-app/src/test/resources/runtimets/testsuite.xml
index 7d1e611..8cf4cd9 100644
--- a/asterix-app/src/test/resources/runtimets/testsuite.xml
+++ b/asterix-app/src/test/resources/runtimets/testsuite.xml
@@ -4292,6 +4292,11 @@
       </compilation-unit>
     </test-case>
     <test-case FilePath="tpch">
+      <compilation-unit name="nest_aggregate">
+        <output-dir compare="Text">nest_aggregate</output-dir>
+      </compilation-unit>
+    </test-case>
+    <test-case FilePath="tpch">
       <compilation-unit name="q10_returned_item">
         <output-dir compare="Text">q10_returned_item</output-dir>
       </compilation-unit>
diff --git a/asterix-om/src/main/java/edu/uci/ics/asterix/om/functions/AsterixBuiltinFunctions.java b/asterix-om/src/main/java/edu/uci/ics/asterix/om/functions/AsterixBuiltinFunctions.java
index 8473fc4..ecfc170 100644
--- a/asterix-om/src/main/java/edu/uci/ics/asterix/om/functions/AsterixBuiltinFunctions.java
+++ b/asterix-om/src/main/java/edu/uci/ics/asterix/om/functions/AsterixBuiltinFunctions.java
@@ -653,6 +653,8 @@
     public static final FunctionIdentifier NUMERIC_ADD = AlgebricksBuiltinFunctions.NUMERIC_ADD;
     public static final FunctionIdentifier IS_NULL = AlgebricksBuiltinFunctions.IS_NULL;
 
+    public static final FunctionIdentifier IS_SYSTEM_NULL = new FunctionIdentifier(FunctionConstants.ASTERIX_NS,
+            "is-system-null", 1);;
     public static final FunctionIdentifier NOT_NULL = new FunctionIdentifier(FunctionConstants.ASTERIX_NS, "not-null",
             1);
     public static final FunctionIdentifier COLLECTION_TO_SEQUENCE = new FunctionIdentifier(
@@ -670,6 +672,7 @@
 
         // first, take care of Algebricks builtin functions
         addFunction(IS_NULL, ABooleanTypeComputer.INSTANCE, true);
+        addFunction(IS_SYSTEM_NULL, ABooleanTypeComputer.INSTANCE, true);
         addFunction(NOT, UnaryBooleanOrNullFunctionTypeComputer.INSTANCE, true);
 
         addPrivateFunction(EQ, BinaryBooleanOrNullFunctionTypeComputer.INSTANCE, true);
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/IsSystemNullDescriptor.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/IsSystemNullDescriptor.java
new file mode 100644
index 0000000..ab9f7e2
--- /dev/null
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/IsSystemNullDescriptor.java
@@ -0,0 +1,82 @@
+/*
+ * 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.asterix.runtime.evaluators.functions;
+
+import java.io.DataOutput;
+
+import edu.uci.ics.asterix.dataflow.data.nontagged.serde.AObjectSerializerDeserializer;
+import edu.uci.ics.asterix.om.base.ABoolean;
+import edu.uci.ics.asterix.om.functions.AsterixBuiltinFunctions;
+import edu.uci.ics.asterix.om.functions.IFunctionDescriptor;
+import edu.uci.ics.asterix.om.functions.IFunctionDescriptorFactory;
+import edu.uci.ics.asterix.om.types.ATypeTag;
+import edu.uci.ics.asterix.runtime.evaluators.base.AbstractScalarFunctionDynamicDescriptor;
+import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
+import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
+import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyEvaluator;
+import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyEvaluatorFactory;
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
+import edu.uci.ics.hyracks.data.std.api.IDataOutputProvider;
+import edu.uci.ics.hyracks.data.std.util.ArrayBackedValueStorage;
+import edu.uci.ics.hyracks.dataflow.common.data.accessors.IFrameTupleReference;
+
+public class IsSystemNullDescriptor extends AbstractScalarFunctionDynamicDescriptor {
+
+    private static final long serialVersionUID = 1L;
+
+    private final static byte SER_SYSTEM_NULL_TYPE_TAG = ATypeTag.SYSTEM_NULL.serialize();
+    public static final IFunctionDescriptorFactory FACTORY = new IFunctionDescriptorFactory() {
+        public IFunctionDescriptor createFunctionDescriptor() {
+            return new IsSystemNullDescriptor();
+        }
+    };
+
+    @Override
+    public ICopyEvaluatorFactory createEvaluatorFactory(final ICopyEvaluatorFactory[] args) throws AlgebricksException {
+        return new ICopyEvaluatorFactory() {
+
+            private static final long serialVersionUID = 1L;
+
+            @Override
+            public ICopyEvaluator createEvaluator(final IDataOutputProvider output) throws AlgebricksException {
+                return new ICopyEvaluator() {
+
+                    private DataOutput out = output.getDataOutput();
+                    private ArrayBackedValueStorage argOut = new ArrayBackedValueStorage();
+                    private ICopyEvaluator eval = args[0].createEvaluator(argOut);
+
+                    @Override
+                    public void evaluate(IFrameTupleReference tuple) throws AlgebricksException {
+                        argOut.reset();
+                        eval.evaluate(tuple);
+                        boolean isSystemNull = argOut.getByteArray()[argOut.getStartOffset()] == SER_SYSTEM_NULL_TYPE_TAG;
+                        ABoolean res = isSystemNull ? ABoolean.TRUE : ABoolean.FALSE;
+                        try {
+                            AObjectSerializerDeserializer.INSTANCE.serialize(res, out);
+                        } catch (HyracksDataException e) {
+                            throw new AlgebricksException(e);
+                        }
+                    }
+                };
+            }
+        };
+    }
+
+    @Override
+    public FunctionIdentifier getIdentifier() {
+        return AsterixBuiltinFunctions.IS_SYSTEM_NULL;
+    }
+
+}
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/formats/NonTaggedDataFormat.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/formats/NonTaggedDataFormat.java
index 4ca39b2..5c2d62d 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/formats/NonTaggedDataFormat.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/formats/NonTaggedDataFormat.java
@@ -186,6 +186,7 @@
 import edu.uci.ics.asterix.runtime.evaluators.functions.HashedWordTokensDescriptor;
 import edu.uci.ics.asterix.runtime.evaluators.functions.InjectFailureDescriptor;
 import edu.uci.ics.asterix.runtime.evaluators.functions.IsNullDescriptor;
+import edu.uci.ics.asterix.runtime.evaluators.functions.IsSystemNullDescriptor;
 import edu.uci.ics.asterix.runtime.evaluators.functions.LenDescriptor;
 import edu.uci.ics.asterix.runtime.evaluators.functions.LikeDescriptor;
 import edu.uci.ics.asterix.runtime.evaluators.functions.NotDescriptor;
@@ -394,6 +395,7 @@
         temp.add(NumericModuloDescriptor.FACTORY);
         temp.add(NumericCaretDescriptor.FACTORY);
         temp.add(IsNullDescriptor.FACTORY);
+        temp.add(IsSystemNullDescriptor.FACTORY);
         temp.add(NotDescriptor.FACTORY);
         temp.add(LenDescriptor.FACTORY);
         temp.add(EmptyStreamAggregateDescriptor.FACTORY);