diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 1247433..cb0299a 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -881,6 +881,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_Gather:
 			pname = sname = "Gather";
 			break;
+		case T_GatherMerge:
+			pname = sname = "Gather Merge";
+			break;
 		case T_IndexScan:
 			pname = sname = "Index Scan";
 			break;
@@ -1370,6 +1373,26 @@ ExplainNode(PlanState *planstate, List *ancestors,
 					ExplainPropertyBool("Single Copy", gather->single_copy, es);
 			}
 			break;
+		case T_GatherMerge:
+			{
+				GatherMerge *gm = (GatherMerge *) plan;
+
+				show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
+				if (plan->qual)
+					show_instrumentation_count("Rows Removed by Filter", 1,
+											   planstate, es);
+				ExplainPropertyInteger("Workers Planned",
+									   gm->num_workers, es);
+				if (es->analyze)
+				{
+					int			nworkers;
+
+					nworkers = ((GatherMergeState *) planstate)->nworkers_launched;
+					ExplainPropertyInteger("Workers Launched",
+										   nworkers, es);
+				}
+			}
+			break;
 		case T_FunctionScan:
 			if (es->verbose)
 			{
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index 51edd4c..7e2f4e2 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -19,7 +19,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execIndexing.o execJunk.o \
        nodeBitmapAnd.o nodeBitmapOr.o \
        nodeBitmapHeapscan.o nodeBitmapIndexscan.o nodeCustom.o nodeGather.o \
        nodeHash.o nodeHashjoin.o nodeIndexscan.o nodeIndexonlyscan.o \
-       nodeLimit.o nodeLockRows.o \
+       nodeLimit.o nodeLockRows.o nodeGatherMerge.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
        nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 554244f..45b36af 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -101,6 +101,7 @@
 #include "executor/nodeModifyTable.h"
 #include "executor/nodeNestloop.h"
 #include "executor/nodeGather.h"
+#include "executor/nodeGatherMerge.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
 #include "executor/nodeSamplescan.h"
@@ -314,6 +315,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												  estate, eflags);
 			break;

+		case T_GatherMerge:
+			result = (PlanState *) ExecInitGatherMerge((GatherMerge *) node,
+													   estate, eflags);
+			break;
+
 		case T_Hash:
 			result = (PlanState *) ExecInitHash((Hash *) node,
 												estate, eflags);
@@ -515,6 +521,10 @@ ExecProcNode(PlanState *node)
 			result = ExecGather((GatherState *) node);
 			break;

+		case T_GatherMergeState:
+			result = ExecGatherMerge((GatherMergeState *) node);
+			break;
+
 		case T_HashState:
 			result = ExecHash((HashState *) node);
 			break;
@@ -673,6 +683,10 @@ ExecEndNode(PlanState *node)
 			ExecEndGather((GatherState *) node);
 			break;

+		case T_GatherMergeState:
+			ExecEndGatherMerge((GatherMergeState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
@@ -806,6 +820,9 @@ ExecShutdownNode(PlanState *node)
 		case T_GatherState:
 			ExecShutdownGather((GatherState *) node);
 			break;
+		case T_GatherMergeState:
+			ExecShutdownGatherMerge((GatherMergeState *) node);
+			break;
 		default:
 			break;
 	}
diff --git a/src/backend/executor/nodeGatherMerge.c b/src/backend/executor/nodeGatherMerge.c
new file mode 100644
index 0000000..fd884a8
--- /dev/null
+++ b/src/backend/executor/nodeGatherMerge.c
@@ -0,0 +1,693 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeGatherMerge.c
+ *	  routines to handle GatherMerge nodes.
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeGatherMerge.c
+ *
+ *-------------------------------------------------------------------------
+ */
+/* INTERFACE ROUTINES
+ *		ExecInitGatherMerge		- initialize the MergeAppend node
+ *		ExecGatherMerge			- retrieve the next tuple from the node
+ *		ExecEndGatherMerge		- shut down the MergeAppend node
+ *		ExecReScanGatherMerge	- rescan the MergeAppend node
+ */
+
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "access/xact.h"
+#include "executor/execdebug.h"
+#include "executor/execParallel.h"
+#include "executor/nodeGatherMerge.h"
+#include "executor/nodeSubplan.h"
+#include "executor/tqueue.h"
+#include "miscadmin.h"
+#include "utils/memutils.h"
+#include "utils/rel.h"
+#include "lib/binaryheap.h"
+
+/*
+ * Tuple array for each worker
+ */
+typedef struct GMReaderTuple
+{
+	HeapTuple  *tuple;
+	int			readCounter;
+	int			nTuples;
+	bool		done;
+}	GMReaderTuple;
+
+/* Tuple array size */
+#define MAX_TUPLE_STORE 10
+
+static int32 heap_compare_slots(Datum a, Datum b, void *arg);
+static TupleTableSlot *gather_merge_getnext(GatherMergeState * gm_state);
+static HeapTuple gm_readnext_tuple(GatherMergeState * gm_state, int nreader, bool force, bool *done);
+static void gather_merge_init(GatherMergeState * gm_state);
+static void ExecShutdownGatherMergeWorkers(GatherMergeState * node);
+static bool gather_merge_readnext(GatherMergeState * gm_state, int reader, bool force);
+static void fill_tuple_array(GatherMergeState * gm_state, int reader);
+
+/* ----------------------------------------------------------------
+ *		ExecInitGather
+ * ----------------------------------------------------------------
+ */
+GatherMergeState *
+ExecInitGatherMerge(GatherMerge * node, EState *estate, int eflags)
+{
+	GatherMergeState *gm_state;
+	Plan	   *outerNode;
+	bool		hasoid;
+	TupleDesc	tupDesc;
+
+	/* Gather merge node doesn't have innerPlan node. */
+	Assert(innerPlan(node) == NULL);
+
+	/*
+	 * create state structure
+	 */
+	gm_state = makeNode(GatherMergeState);
+	gm_state->ps.plan = (Plan *) node;
+	gm_state->ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &gm_state->ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	gm_state->ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) gm_state);
+	gm_state->ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) gm_state);
+
+	/*
+	 * tuple table initialization
+	 */
+	gm_state->funnel_slot = ExecInitExtraTupleSlot(estate);
+	ExecInitResultTupleSlot(estate, &gm_state->ps);
+
+	/*
+	 * now initialize outer plan
+	 */
+	outerNode = outerPlan(node);
+	outerPlanState(gm_state) = ExecInitNode(outerNode, estate, eflags);
+
+	gm_state->ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&gm_state->ps);
+	ExecAssignProjectionInfo(&gm_state->ps, NULL);
+
+	gm_state->gm_initialized = false;
+
+	/*
+	 * initialize sort-key information
+	 */
+	if (node->numCols)
+	{
+		int			i;
+
+		gm_state->gm_nkeys = node->numCols;
+		gm_state->gm_sortkeys = palloc0(sizeof(SortSupportData) * node->numCols);
+		for (i = 0; i < node->numCols; i++)
+		{
+			SortSupport sortKey = gm_state->gm_sortkeys + i;
+
+			sortKey->ssup_cxt = CurrentMemoryContext;
+			sortKey->ssup_collation = node->collations[i];
+			sortKey->ssup_nulls_first = node->nullsFirst[i];
+			sortKey->ssup_attno = node->sortColIdx[i];
+
+			/*
+			 * We don't perform abbreviated key conversion here, for the same
+			 * reasons that it isn't used in MergeAppend
+			 */
+			sortKey->abbreviate = false;
+
+			PrepareSortSupportFromOrderingOp(node->sortOperators[i], sortKey);
+		}
+	}
+
+	/*
+	 * Initialize funnel slot to same tuple descriptor as outer plan.
+	 */
+	if (!ExecContextForcesOids(&gm_state->ps, &hasoid))
+		hasoid = false;
+	tupDesc = ExecTypeFromTL(outerNode->targetlist, hasoid);
+	ExecSetSlotDescriptor(gm_state->funnel_slot, tupDesc);
+
+	return gm_state;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecGatherMerge(node)
+ *
+ *		Scans the relation via multiple workers and returns
+ *		the next qualifying tuple.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecGatherMerge(GatherMergeState * node)
+{
+	TupleTableSlot *fslot = node->funnel_slot;
+	int			i;
+	TupleTableSlot *slot;
+	TupleTableSlot *resultSlot;
+	ExprDoneCond isDone;
+	ExprContext *econtext;
+
+	/*
+	 * Initialize the parallel context and workers on first execution. We do
+	 * this on first execution rather than during node initialization, as it
+	 * needs to allocate large dynamic segment, so it is better to do if it is
+	 * really needed.
+	 */
+	if (!node->initialized)
+	{
+		EState	   *estate = node->ps.state;
+		GatherMerge *gm = (GatherMerge *) node->ps.plan;
+
+		/*
+		 * Sometimes we might have to run without parallelism; but if parallel
+		 * mode is active then we can try to fire up some workers.
+		 */
+		if (gm->num_workers > 0 && IsInParallelMode())
+		{
+			ParallelContext *pcxt;
+			bool		got_any_worker = false;
+
+			/* Initialize the workers required to execute Gather node. */
+			if (!node->pei)
+				node->pei = ExecInitParallelPlan(node->ps.lefttree,
+												 estate,
+												 gm->num_workers);
+
+			/*
+			 * Register backend workers. We might not get as many as we
+			 * requested, or indeed any at all.
+			 */
+			pcxt = node->pei->pcxt;
+			LaunchParallelWorkers(pcxt);
+			node->nworkers_launched = pcxt->nworkers_launched;
+
+			/* Set up tuple queue readers to read the results. */
+			if (pcxt->nworkers_launched > 0)
+			{
+				node->nreaders = 0;
+				node->reader =
+					palloc(pcxt->nworkers_launched * sizeof(TupleQueueReader *));
+
+				Assert(gm->numCols);
+
+				for (i = 0; i < pcxt->nworkers_launched; ++i)
+				{
+					if (pcxt->worker[i].bgwhandle == NULL)
+						continue;
+
+					shm_mq_set_handle(node->pei->tqueue[i],
+									  pcxt->worker[i].bgwhandle);
+					node->reader[node->nreaders] =
+						CreateTupleQueueReader(node->pei->tqueue[i],
+											   fslot->tts_tupleDescriptor);
+					node->nreaders++;
+					got_any_worker = true;
+				}
+			}
+
+			/* No workers?	Then never mind. */
+			if (!got_any_worker ||
+				node->nreaders < 2)
+			{
+				ExecShutdownGatherMergeWorkers(node);
+				node->nreaders = 0;
+			}
+		}
+
+		/* always allow leader to participate into gather merge */
+		node->need_to_scan_locally = true;
+		node->initialized = true;
+	}
+
+	/*
+	 * Check to see if we're still projecting out tuples from a previous scan
+	 * tuple (because there is a function-returning-set in the projection
+	 * expressions).  If so, try to project another one.
+	 */
+	if (node->ps.ps_TupFromTlist)
+	{
+		resultSlot = ExecProject(node->ps.ps_ProjInfo, &isDone);
+		if (isDone == ExprMultipleResult)
+			return resultSlot;
+		/* Done with that source tuple... */
+		node->ps.ps_TupFromTlist = false;
+	}
+
+	/*
+	 * Reset per-tuple memory context to free any expression evaluation
+	 * storage allocated in the previous tuple cycle.  Note we can't do this
+	 * until we're done projecting.
+	 */
+	econtext = node->ps.ps_ExprContext;
+	ResetExprContext(econtext);
+
+	/* Get and return the next tuple, projecting if necessary. */
+	for (;;)
+	{
+		/*
+		 * Get next tuple, either from one of our workers, or by running the
+		 * plan ourselves.
+		 */
+		slot = gather_merge_getnext(node);
+		if (TupIsNull(slot))
+			return NULL;
+
+		/*
+		 * form the result tuple using ExecProject(), and return it --- unless
+		 * the projection produces an empty set, in which case we must loop
+		 * back around for another tuple
+		 */
+		econtext->ecxt_outertuple = slot;
+		resultSlot = ExecProject(node->ps.ps_ProjInfo, &isDone);
+
+		if (isDone != ExprEndResult)
+		{
+			node->ps.ps_TupFromTlist = (isDone == ExprMultipleResult);
+			return resultSlot;
+		}
+	}
+
+	return slot;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndGatherMerge
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndGatherMerge(GatherMergeState * node)
+{
+	ExecShutdownGatherMerge(node);
+	ExecFreeExprContext(&node->ps);
+	ExecClearTuple(node->ps.ps_ResultTupleSlot);
+	ExecEndNode(outerPlanState(node));
+}
+
+/* ----------------------------------------------------------------
+ *		ExecShutdownGatherMerge
+ *
+ *		Destroy the setup for parallel workers including parallel context.
+ *		Collect all the stats after workers are stopped, else some work
+ *		done by workers won't be accounted.
+ * ----------------------------------------------------------------
+ */
+void
+ExecShutdownGatherMerge(GatherMergeState * node)
+{
+	ExecShutdownGatherMergeWorkers(node);
+
+	/* Now destroy the parallel context. */
+	if (node->pei != NULL)
+	{
+		ExecParallelCleanup(node->pei);
+		node->pei = NULL;
+	}
+}
+
+/* ----------------------------------------------------------------
+ *		ExecReScanGatherMerge
+ *
+ *		Re-initialize the workers and rescans a relation via them.
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanGatherMerge(GatherMergeState * node)
+{
+	/*
+	 * Re-initialize the parallel workers to perform rescan of relation. We
+	 * want to gracefully shutdown all the workers so that they should be able
+	 * to propagate any error or other information to master backend before
+	 * dying.  Parallel context will be reused for rescan.
+	 */
+	ExecShutdownGatherMergeWorkers(node);
+
+	node->initialized = false;
+
+	if (node->pei)
+		ExecParallelReinitialize(node->pei);
+
+	ExecReScan(node->ps.lefttree);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecShutdownGatherMergeWorkers
+ *
+ *		Destroy the parallel workers.  Collect all the stats after
+ *		workers are stopped, else some work done by workers won't be
+ *		accounted.
+ * ----------------------------------------------------------------
+ */
+static void
+ExecShutdownGatherMergeWorkers(GatherMergeState * node)
+{
+	/* Shut down tuple queue readers before shutting down workers. */
+	if (node->reader != NULL)
+	{
+		int			i;
+
+		for (i = 0; i < node->nreaders; ++i)
+			if (node->reader[i])
+				DestroyTupleQueueReader(node->reader[i]);
+
+		pfree(node->reader);
+		node->reader = NULL;
+	}
+
+	/* Now shut down the workers. */
+	if (node->pei != NULL)
+		ExecParallelFinish(node->pei);
+}
+
+/*
+ * Initialize the Gather merge tuple read.
+ *
+ * Pull atleast single tuple from each worker + leader and set up the heap.
+ */
+static void
+gather_merge_init(GatherMergeState * gm_state)
+{
+	TupleTableSlot *fslot = gm_state->funnel_slot;
+	int			nreaders = gm_state->nreaders;
+	bool		initialize = true;
+	int			i;
+
+	/*
+	 * Allocate gm_slots for the number of worker + one more slot for leader.
+	 * Last slot is always for leader. Leader always calls ExecProcNode() to
+	 * read the tuple which will return the TupleTableSlot. Later it will
+	 * directly get assigned to gm_slot. So just initialize leader gm_slot
+	 * with NULL. For other slots below code will call
+	 * ExecInitExtraTupleSlot() which will do the initialization of worker
+	 * slots.
+	 */
+	gm_state->gm_slots =
+		palloc((gm_state->nreaders + 1) * sizeof(TupleTableSlot *));
+	gm_state->gm_slots[gm_state->nreaders] = NULL;
+
+	/* Initialize the tuple slot and tuple array for each worker */
+	gm_state->gm_tuple = (GMReaderTuple *) palloc0(sizeof(GMReaderTuple) * (gm_state->nreaders));
+	for (i = 0; i < gm_state->nreaders; i++)
+	{
+		/* Allocate the tuple array with MAX_TUPLE_STORE size */
+		gm_state->gm_tuple[i].tuple = (HeapTuple *) palloc0(sizeof(HeapTuple) * MAX_TUPLE_STORE);
+
+		/* Initialize slot for worker */
+		gm_state->gm_slots[i] = ExecInitExtraTupleSlot(gm_state->ps.state);
+		ExecSetSlotDescriptor(gm_state->gm_slots[i],
+							  fslot->tts_tupleDescriptor);
+	}
+
+	/* Allocate the resources for the sort */
+	gm_state->gm_heap = binaryheap_allocate(gm_state->nreaders + 1, heap_compare_slots, gm_state);
+
+	/*
+	 * First try to read tuple for each worker (including leader) into nowait
+	 * mode, so that we initialize read from each worker as well as leader.
+	 * After this if all worker unable to produce the tuple, then re-read and
+	 * this time read the tuple into wait mode. For the worker, which was able
+	 * to produced single tuple in the earlier loop, just fill the tuple array
+	 * if more tuples available.
+	 */
+reread:
+	for (i = 0; i < nreaders + 1; i++)
+	{
+		if (TupIsNull(gm_state->gm_slots[i]) ||
+			gm_state->gm_slots[i]->tts_isempty)
+		{
+			if (gather_merge_readnext(gm_state, i, initialize ? false : true))
+			{
+				binaryheap_add_unordered(gm_state->gm_heap,
+										 Int32GetDatum(i));
+			}
+		}
+		else
+			fill_tuple_array(gm_state, i);
+	}
+	initialize = false;
+
+	for (i = 0; i < nreaders; i++)
+		if (TupIsNull(gm_state->gm_slots[i]) || gm_state->gm_slots[i]->tts_isempty)
+			goto reread;
+
+	binaryheap_build(gm_state->gm_heap);
+	gm_state->gm_initialized = true;
+}
+
+/*
+ * Read the next tuple for gather merge.
+ *
+ * Function fetch the sorted tuple out of the heap.
+ */
+static TupleTableSlot *
+gather_merge_getnext(GatherMergeState * gm_state)
+{
+	TupleTableSlot *fslot = gm_state->funnel_slot;
+	int			i;
+
+	/*
+	 * First time through: pull the first tuple from each participate, and set
+	 * up the heap.
+	 */
+	if (gm_state->gm_initialized == false)
+		gather_merge_init(gm_state);
+	else
+	{
+		/*
+		 * Otherwise, pull the next tuple from whichever participate we
+		 * returned from last time, and reinsert the index into the heap,
+		 * because it might now compare differently against the existing
+		 * elements of the heap.
+		 */
+		i = DatumGetInt32(binaryheap_first(gm_state->gm_heap));
+
+		if (gather_merge_readnext(gm_state, i, true))
+			binaryheap_replace_first(gm_state->gm_heap, Int32GetDatum(i));
+		else
+			(void) binaryheap_remove_first(gm_state->gm_heap);
+	}
+
+	if (binaryheap_empty(gm_state->gm_heap))
+	{
+		/* All the queues are exhausted, and so is the heap */
+		return ExecClearTuple(fslot);
+	}
+	else
+	{
+		i = DatumGetInt32(binaryheap_first(gm_state->gm_heap));
+		return gm_state->gm_slots[i];
+	}
+
+	return ExecClearTuple(fslot);
+}
+
+/*
+ * Read the tuple for given reader into nowait mode, and fill the tuple array.
+ */
+static void
+fill_tuple_array(GatherMergeState * gm_state, int reader)
+{
+	GMReaderTuple *gm_tuple = &gm_state->gm_tuple[reader];
+	int			i;
+
+	/* Last slot is for leader and we don't build tuple array for leader */
+	if (reader == gm_state->nreaders)
+		return;
+
+	/*
+	 * We here because we already read all the tuples from the tuple array, so
+	 * initialize the counter to zero.
+	 */
+	if (gm_tuple->nTuples == gm_tuple->readCounter)
+		gm_tuple->nTuples = gm_tuple->readCounter = 0;
+
+	/* Tuple array is already full? */
+	if (gm_tuple->nTuples == MAX_TUPLE_STORE)
+		return;
+
+	for (i = gm_tuple->nTuples; i < MAX_TUPLE_STORE; i++)
+	{
+		gm_tuple->tuple[i] = gm_readnext_tuple(gm_state,
+											   reader,
+											   false,
+											   &gm_tuple->done);
+		if (!HeapTupleIsValid(gm_tuple->tuple[i]))
+			break;
+		gm_tuple->nTuples++;
+	}
+}
+
+/*
+ * Function attempt to read tuple for the given reader and store it into reader
+ * tuple slot.
+ *
+ * If the worker tuple array contains any tuple then just read tuple from the
+ * tuple array. Other wise read the tuple from the queue and also attempt to
+ * fill the tuple array.
+ *
+ * When force is true, function reads the tuple into wait mode. For gather
+ * merge we need to fill the slot from which we returned the earlier tuple, so
+ * this require tuple to be read into wait mode. During initialization phase,
+ * once we try to read the tuple into no-wait mode as we want to initialize all
+ * the readers. Refer gather_merge_init() for more details.
+ *
+ * Function returns true if found tuple for the reader, otherwise returns
+ * false.
+ */
+static bool
+gather_merge_readnext(GatherMergeState * gm_state, int reader, bool force)
+{
+	HeapTuple	tup = NULL;
+
+	/* We here for leader? */
+	if (gm_state->nreaders == reader)
+	{
+		if (gm_state->need_to_scan_locally)
+		{
+			PlanState  *outerPlan = outerPlanState(gm_state);
+			TupleTableSlot *outerTupleSlot;
+
+			outerTupleSlot = ExecProcNode(outerPlan);
+
+			if (!TupIsNull(outerTupleSlot))
+			{
+				gm_state->gm_slots[reader] = outerTupleSlot;
+				return true;
+			}
+			gm_state->need_to_scan_locally = false;
+		}
+		return false;
+	}
+	/* Does tuple array have any avaiable tuples? */
+	else if (gm_state->gm_tuple[reader].nTuples >
+			 gm_state->gm_tuple[reader].readCounter)
+	{
+		GMReaderTuple *gm_tuple = &gm_state->gm_tuple[reader];
+
+		tup = gm_tuple->tuple[gm_tuple->readCounter++];
+	}
+	/* reader exhausted? */
+	else if (gm_state->gm_tuple[reader].done)
+	{
+		DestroyTupleQueueReader(gm_state->reader[reader]);
+		gm_state->reader[reader] = NULL;
+		return false;
+	}
+	else
+	{
+		tup = gm_readnext_tuple(gm_state, reader, force, NULL);
+
+		/*
+		 * try to read more tuple into nowait mode and store it into the tuple
+		 * array.
+		 */
+		if (HeapTupleIsValid(tup))
+			fill_tuple_array(gm_state, reader);
+		else
+			return false;
+	}
+
+	Assert(HeapTupleIsValid(tup));
+
+	/* Build the TupleTableSlot for the given tuple */
+	ExecStoreTuple(tup,			/* tuple to store */
+				   gm_state->gm_slots[reader],	/* slot in which to store the
+												 * tuple */
+				   InvalidBuffer,		/* buffer associated with this tuple */
+				   true);		/* pfree this pointer if not from heap */
+
+	return true;
+}
+
+/*
+ * Attempt to read a tuple from given reader.
+ */
+static HeapTuple
+gm_readnext_tuple(GatherMergeState * gm_state, int nreader, bool force, bool *done)
+{
+	TupleQueueReader *reader;
+	HeapTuple	tup = NULL;
+
+	if (done != NULL)
+		*done = false;
+
+	/* Check for async events, particularly messages from workers. */
+	CHECK_FOR_INTERRUPTS();
+
+	/* Attempt to read a tuple. */
+	reader = gm_state->reader[nreader];
+	tup = TupleQueueReaderNext(reader, force ? false : true, done);
+
+	return tup;
+}
+
+/*
+ * We have one slot for each item in the heap array.  We use SlotNumber
+ * to store slot indexes.  This doesn't actually provide any formal
+ * type-safety, but it makes the code more self-documenting.
+ */
+typedef int32 SlotNumber;
+
+/*
+ * Compare the tuples in the two given slots.
+ */
+static int32
+heap_compare_slots(Datum a, Datum b, void *arg)
+{
+	GatherMergeState *node = (GatherMergeState *) arg;
+	SlotNumber	slot1 = DatumGetInt32(a);
+	SlotNumber	slot2 = DatumGetInt32(b);
+
+	TupleTableSlot *s1 = node->gm_slots[slot1];
+	TupleTableSlot *s2 = node->gm_slots[slot2];
+	int			nkey;
+
+	Assert(!TupIsNull(s1));
+	Assert(!TupIsNull(s2));
+
+	for (nkey = 0; nkey < node->gm_nkeys; nkey++)
+	{
+		SortSupport sortKey = node->gm_sortkeys + nkey;
+		AttrNumber	attno = sortKey->ssup_attno;
+		Datum		datum1,
+					datum2;
+		bool		isNull1,
+					isNull2;
+		int			compare;
+
+		datum1 = slot_getattr(s1, attno, &isNull1);
+		datum2 = slot_getattr(s2, attno, &isNull2);
+
+		compare = ApplySortComparator(datum1, isNull1,
+									  datum2, isNull2,
+									  sortKey);
+		if (compare != 0)
+			return -compare;
+	}
+	return 0;
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 71714bc..8b92c1a 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -341,6 +341,31 @@ _copyGather(const Gather *from)
 	return newnode;
 }

+/*
+ * _copyGatherMerge
+ */
+static GatherMerge *
+_copyGatherMerge(const GatherMerge *from)
+{
+	GatherMerge	   *newnode = makeNode(GatherMerge);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyPlanFields((const Plan *) from, (Plan *) newnode);
+
+	/*
+	 * copy remainder of node
+	 */
+	COPY_SCALAR_FIELD(num_workers);
+	COPY_SCALAR_FIELD(numCols);
+	COPY_POINTER_FIELD(sortColIdx, from->numCols * sizeof(AttrNumber));
+	COPY_POINTER_FIELD(sortOperators, from->numCols * sizeof(Oid));
+	COPY_POINTER_FIELD(collations, from->numCols * sizeof(Oid));
+	COPY_POINTER_FIELD(nullsFirst, from->numCols * sizeof(bool));
+
+	return newnode;
+}

 /*
  * CopyScanFields
@@ -4343,6 +4368,9 @@ copyObject(const void *from)
 		case T_Gather:
 			retval = _copyGather(from);
 			break;
+		case T_GatherMerge:
+			retval = _copyGatherMerge(from);
+			break;
 		case T_SeqScan:
 			retval = _copySeqScan(from);
 			break;
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index ae86954..5dea0f7 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -447,6 +447,35 @@ _outGather(StringInfo str, const Gather *node)
 }

 static void
+_outGatherMerge(StringInfo str, const GatherMerge *node)
+{
+	int		i;
+
+	WRITE_NODE_TYPE("GATHERMERGE");
+
+	_outPlanInfo(str, (const Plan *) node);
+
+	WRITE_INT_FIELD(num_workers);
+	WRITE_INT_FIELD(numCols);
+
+	appendStringInfoString(str, " :sortColIdx");
+	for (i = 0; i < node->numCols; i++)
+		appendStringInfo(str, " %d", node->sortColIdx[i]);
+
+	appendStringInfoString(str, " :sortOperators");
+	for (i = 0; i < node->numCols; i++)
+		appendStringInfo(str, " %u", node->sortOperators[i]);
+
+	appendStringInfoString(str, " :collations");
+	for (i = 0; i < node->numCols; i++)
+		appendStringInfo(str, " %u", node->collations[i]);
+
+	appendStringInfoString(str, " :nullsFirst");
+	for (i = 0; i < node->numCols; i++)
+		appendStringInfo(str, " %s", booltostr(node->nullsFirst[i]));
+}
+
+static void
 _outScan(StringInfo str, const Scan *node)
 {
 	WRITE_NODE_TYPE("SCAN");
@@ -1964,6 +1993,18 @@ _outLimitPath(StringInfo str, const LimitPath *node)
 }

 static void
+_outGatherMergePath(StringInfo str, const GatherMergePath *node)
+{
+	WRITE_NODE_TYPE("GATHERMERGEPATH");
+
+	_outPathInfo(str, (const Path *) node);
+
+	WRITE_NODE_FIELD(subpath);
+	WRITE_INT_FIELD(num_workers);
+	WRITE_BOOL_FIELD(single_copy);
+}
+
+static void
 _outNestPath(StringInfo str, const NestPath *node)
 {
 	WRITE_NODE_TYPE("NESTPATH");
@@ -3322,6 +3363,9 @@ outNode(StringInfo str, const void *obj)
 			case T_Gather:
 				_outGather(str, obj);
 				break;
+			case T_GatherMerge:
+				_outGatherMerge(str, obj);
+				break;
 			case T_Scan:
 				_outScan(str, obj);
 				break;
@@ -3649,6 +3693,9 @@ outNode(StringInfo str, const void *obj)
 			case T_LimitPath:
 				_outLimitPath(str, obj);
 				break;
+			case T_GatherMergePath:
+				_outGatherMergePath(str, obj);
+				break;
 			case T_NestPath:
 				_outNestPath(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 917e6c8..77a452e 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -2075,6 +2075,26 @@ _readGather(void)
 }

 /*
+ * _readGatherMerge
+ */
+static GatherMerge *
+_readGatherMerge(void)
+{
+	READ_LOCALS(GatherMerge);
+
+	ReadCommonPlan(&local_node->plan);
+
+	READ_INT_FIELD(num_workers);
+	READ_INT_FIELD(numCols);
+	READ_ATTRNUMBER_ARRAY(sortColIdx, local_node->numCols);
+	READ_OID_ARRAY(sortOperators, local_node->numCols);
+	READ_OID_ARRAY(collations, local_node->numCols);
+	READ_BOOL_ARRAY(nullsFirst, local_node->numCols);
+
+	READ_DONE();
+}
+
+/*
  * _readHash
  */
 static Hash *
@@ -2477,6 +2497,8 @@ parseNodeString(void)
 		return_value = _readUnique();
 	else if (MATCH("GATHER", 6))
 		return_value = _readGather();
+	else if (MATCH("GATHERMERGE", 11))
+		return_value = _readGatherMerge();
 	else if (MATCH("HASH", 4))
 		return_value = _readHash();
 	else if (MATCH("SETOP", 5))
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 2a49639..5dbb83e 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -126,6 +126,7 @@ bool		enable_nestloop = true;
 bool		enable_material = true;
 bool		enable_mergejoin = true;
 bool		enable_hashjoin = true;
+bool		enable_gathermerge = true;

 typedef struct
 {
@@ -391,6 +392,70 @@ cost_gather(GatherPath *path, PlannerInfo *root,
 }

 /*
+ * cost_gather_merge
+ *	  Determines and returns the cost of gather merge path.
+ *
+ * GatherMerge merges several pre-sorted input streams, using a heap that at
+ * any given instant holds the next tuple from each stream. If there are N
+ * streams, we need about N*log2(N) tuple comparisons to construct the heap at
+ * startup, and then for each output tuple, about log2(N) comparisons to delete
+ * the top heap entry and another log2(N) comparisons to insert its successor
+ * from the same stream.
+ *
+ * The heap is never spilled to disk, since we assume N is not very large. So
+ * this is much simple then cost_sort.
+ */
+void
+cost_gather_merge(GatherMergePath *path, PlannerInfo *root,
+				  RelOptInfo *rel, ParamPathInfo *param_info,
+				  Cost input_startup_cost, Cost input_total_cost)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	Cost		comparison_cost;
+	double		N;
+	double		logN;
+
+	/* Mark the path with the correct row estimate */
+	if (param_info)
+		path->path.rows = param_info->ppi_rows;
+	else
+		path->path.rows = path->subpath->rows;
+
+	if (!enable_gathermerge)
+		startup_cost += disable_cost;
+
+	/*
+	 * Avoid log(0)...
+	 */
+	N = (path->num_workers < 2) ? 2.0 : (double) path->num_workers;
+	logN = LOG2(N);
+
+	/* Assumed cost per tuple comparison */
+	comparison_cost = 2.0 * cpu_operator_cost;
+
+	/* Heap creation cost */
+	startup_cost += comparison_cost * N * logN;
+
+	/* Per-tuple heap maintenance cost */
+	run_cost += path->path.rows * comparison_cost * 2.0 * logN;
+
+	/* small cost for heap management, like cost_merge_append */
+	run_cost += cpu_operator_cost * path->path.rows;
+
+	/*
+	 * Parallel setup and communication cost. For Gather Merge, require tuple
+	 * to be read into wait mode from each worker, so considering some extra
+	 * cost for the same.
+	 */
+	startup_cost += parallel_setup_cost;
+	run_cost += parallel_tuple_cost * path->path.rows;
+
+	path->path.startup_cost = startup_cost + input_startup_cost;
+	path->path.total_cost = (startup_cost + run_cost + input_total_cost);
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 47158f6..96bed2e 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -270,6 +270,11 @@ static ModifyTable *make_modifytable(PlannerInfo *root,
 				 List *resultRelations, List *subplans,
 				 List *withCheckOptionLists, List *returningLists,
 				 List *rowMarks, OnConflictExpr *onconflict, int epqParam);
+static GatherMerge *create_gather_merge_plan(PlannerInfo *root,
+											 GatherMergePath *best_path);
+static GatherMerge *make_gather_merge(List *qptlist, List *qpqual,
+									  int nworkers, bool single_copy,
+									  Plan *subplan);

 /*
@@ -463,6 +468,10 @@ create_plan_recurse(PlannerInfo *root, Path *best_path, int flags)
 											  (LimitPath *) best_path,
 											  flags);
 			break;
+		case T_GatherMerge:
+			plan = (Plan *) create_gather_merge_plan(root,
+												(GatherMergePath *) best_path);
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) best_path->pathtype);
@@ -2246,6 +2255,90 @@ create_limit_plan(PlannerInfo *root, LimitPath *best_path, int flags)
 	return plan;
 }

+/*
+ * create_gather_merge_plan
+ *
+ *	  Create a Gather merge plan for 'best_path' and (recursively)
+ *	  plans for its subpaths.
+ */
+static GatherMerge *
+create_gather_merge_plan(PlannerInfo *root, GatherMergePath *best_path)
+{
+	GatherMerge *gm_plan;
+	Plan	   *subplan;
+	List	   *pathkeys = best_path->path.pathkeys;
+	int			numsortkeys;
+	AttrNumber *sortColIdx;
+	Oid		   *sortOperators;
+	Oid		   *collations;
+	bool	   *nullsFirst;
+
+	subplan = create_plan_recurse(root, best_path->subpath, CP_EXACT_TLIST);
+
+	gm_plan = make_gather_merge(subplan->targetlist,
+								NIL,
+								best_path->num_workers,
+								best_path->single_copy,
+								subplan);
+
+	copy_generic_path_info(&gm_plan->plan, &best_path->path);
+
+	if (pathkeys)
+	{
+		/* Compute sort column info, and adjust GatherMerge tlist as needed */
+		(void) prepare_sort_from_pathkeys(&gm_plan->plan, pathkeys,
+										  best_path->path.parent->relids,
+										  NULL,
+										  true,
+										  &gm_plan->numCols,
+										  &gm_plan->sortColIdx,
+										  &gm_plan->sortOperators,
+										  &gm_plan->collations,
+										  &gm_plan->nullsFirst);
+
+
+		/* Compute sort column info, and adjust subplan's tlist as needed */
+		subplan = prepare_sort_from_pathkeys(subplan, pathkeys,
+											 best_path->subpath->parent->relids,
+											 gm_plan->sortColIdx,
+											 false,
+											 &numsortkeys,
+											 &sortColIdx,
+											 &sortOperators,
+											 &collations,
+											 &nullsFirst);
+
+		/*
+		 * Check that we got the same sort key information.  We just Assert
+		 * that the sortops match, since those depend only on the pathkeys;
+		 * but it seems like a good idea to check the sort column numbers
+		 * explicitly, to ensure the tlists really do match up.
+		 */
+		Assert(numsortkeys == gm_plan->numCols);
+		if (memcmp(sortColIdx, gm_plan->sortColIdx,
+				   numsortkeys * sizeof(AttrNumber)) != 0)
+			elog(ERROR, "GatherMerge child's targetlist doesn't match GatherMerge");
+		Assert(memcmp(sortOperators, gm_plan->sortOperators,
+					  numsortkeys * sizeof(Oid)) == 0);
+		Assert(memcmp(collations, gm_plan->collations,
+					  numsortkeys * sizeof(Oid)) == 0);
+		Assert(memcmp(nullsFirst, gm_plan->nullsFirst,
+					  numsortkeys * sizeof(bool)) == 0);
+
+		/* Now, insert a Sort node if subplan isn't sufficiently ordered */
+		if (!pathkeys_contained_in(pathkeys, best_path->subpath->pathkeys))
+			subplan = (Plan *) make_sort(subplan, numsortkeys,
+										 sortColIdx, sortOperators,
+										 collations, nullsFirst);
+
+		gm_plan->plan.lefttree = subplan;
+	}
+
+	/* use parallel mode for parallel plans. */
+	root->glob->parallelModeNeeded = true;
+
+	return gm_plan;
+}

 /*****************************************************************************
  *
@@ -5902,6 +5995,26 @@ make_gather(List *qptlist,
 	return node;
 }

+static GatherMerge *
+make_gather_merge(List *qptlist,
+				  List *qpqual,
+				  int nworkers,
+				  bool single_copy,
+				  Plan *subplan)
+{
+	GatherMerge	*node = makeNode(GatherMerge);
+	Plan		*plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = subplan;
+	plan->righttree = NULL;
+	node->num_workers = nworkers;
+
+	return node;
+}
+
 /*
  * distinctList is a list of SortGroupClauses, identifying the targetlist
  * items that should be considered by the SetOp filter.  The input path must
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index f657ffc..7339f03 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -3719,14 +3719,59 @@ create_grouping_paths(PlannerInfo *root,

 		/*
 		 * Now generate a complete GroupAgg Path atop of the cheapest partial
-		 * path. We need only bother with the cheapest path here, as the
-		 * output of Gather is never sorted.
+		 * path. We generate a Gather path based on the cheapest partial path,
+		 * and a GatherMerge path for each partial path that is properly sorted.
 		 */
 		if (grouped_rel->partial_pathlist)
 		{
 			Path	   *path = (Path *) linitial(grouped_rel->partial_pathlist);
 			double		total_groups = path->rows * path->parallel_workers;

+			/*
+			 * GatherMerge is always sorted, so if there is GROUP BY clause,
+			 * try to generate GatherMerge path for each partial path.
+			 */
+			if (parse->groupClause)
+			{
+				foreach(lc, grouped_rel->partial_pathlist)
+				{
+					Path	   *gmpath = (Path *) lfirst(lc);
+
+					if (!pathkeys_contained_in(root->group_pathkeys, gmpath->pathkeys))
+						continue;
+
+					/* create gather merge path */
+					gmpath = (Path *) create_gather_merge_path(root,
+															   grouped_rel,
+															   gmpath,
+															   NULL,
+															   root->group_pathkeys,
+															   NULL);
+
+					if (parse->hasAggs)
+						add_path(grouped_rel, (Path *)
+								 create_agg_path(root,
+												 grouped_rel,
+												 gmpath,
+												 target,
+												 parse->groupClause ? AGG_SORTED : AGG_PLAIN,
+												 AGGSPLIT_FINAL_DESERIAL,
+												 parse->groupClause,
+												 (List *) parse->havingQual,
+												 &agg_final_costs,
+												 dNumGroups));
+					else
+						add_path(grouped_rel, (Path *)
+								create_group_path(root,
+												  grouped_rel,
+												  gmpath,
+												  target,
+												  parse->groupClause,
+												  (List *) parse->havingQual,
+												  dNumGroups));
+				}
+			}
+
 			path = (Path *) create_gather_path(root,
 											   grouped_rel,
 											   path,
@@ -3864,6 +3909,12 @@ create_grouping_paths(PlannerInfo *root,
 	/* Now choose the best path(s) */
 	set_cheapest(grouped_rel);

+	/*
+	 * Partial pathlist generated for grouped relation are no further useful,
+	 * so just reset it with null.
+	 */
+	grouped_rel->partial_pathlist = NIL;
+
 	return grouped_rel;
 }

@@ -4160,6 +4211,36 @@ create_distinct_paths(PlannerInfo *root,
 			}
 		}

+		/*
+		 * Generate GatherMerge path for each partial path.
+		 */
+		foreach(lc, input_rel->partial_pathlist)
+		{
+			Path	   *path = (Path *) lfirst(lc);
+
+			if (!pathkeys_contained_in(needed_pathkeys, path->pathkeys))
+			{
+				path = (Path *) create_sort_path(root, distinct_rel,
+												 path,
+												 needed_pathkeys,
+												 -1.0);
+			}
+
+			/* create gather merge path */
+			path = (Path *) create_gather_merge_path(root,
+													 distinct_rel,
+													 path,
+													 NULL,
+													 needed_pathkeys,
+													 NULL);
+			add_path(distinct_rel, (Path *)
+					 create_upper_unique_path(root,
+											  distinct_rel,
+											  path,
+											  list_length(root->distinct_pathkeys),
+											  numDistinctRows));
+		}
+
 		/* For explicit-sort case, always use the more rigorous clause */
 		if (list_length(root->distinct_pathkeys) <
 			list_length(root->sort_pathkeys))
@@ -4304,6 +4385,39 @@ create_ordered_paths(PlannerInfo *root,
 	ordered_rel->useridiscurrent = input_rel->useridiscurrent;
 	ordered_rel->fdwroutine = input_rel->fdwroutine;

+	foreach(lc, input_rel->partial_pathlist)
+	{
+		Path	   *path = (Path *) lfirst(lc);
+		bool		is_sorted;
+
+		is_sorted = pathkeys_contained_in(root->sort_pathkeys,
+										  path->pathkeys);
+		if (!is_sorted)
+		{
+			/* An explicit sort here can take advantage of LIMIT */
+			path = (Path *) create_sort_path(root,
+											 ordered_rel,
+											 path,
+											 root->sort_pathkeys,
+											 limit_tuples);
+		}
+
+		/* create gather merge path */
+		path = (Path *) create_gather_merge_path(root,
+												 ordered_rel,
+												 path,
+												 target,
+												 root->sort_pathkeys,
+												 NULL);
+
+		/* Add projection step if needed */
+		if (path->pathtarget != target)
+			path = apply_projection_to_path(root, ordered_rel,
+											path, target);
+
+		add_path(ordered_rel, path);
+	}
+
 	foreach(lc, input_rel->pathlist)
 	{
 		Path	   *path = (Path *) lfirst(lc);
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index d10a983..d14db7d 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -605,6 +605,7 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 			break;

 		case T_Gather:
+		case T_GatherMerge:
 			set_upper_references(root, plan, rtoffset);
 			break;

diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 263ba45..760f519 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2682,6 +2682,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 		case T_Sort:
 		case T_Unique:
 		case T_Gather:
+		case T_GatherMerge:
 		case T_SetOp:
 		case T_Group:
 			break;
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index abb7507..f83cd77 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -1630,6 +1630,66 @@ create_unique_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
 }

 /*
+ * create_gather_merge_path
+ *
+ *	  Creates a path corresponding to a gather merge scan, returning
+ *	  the pathnode.
+ */
+GatherMergePath *
+create_gather_merge_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
+						 PathTarget *target, List *pathkeys,
+						 Relids required_outer)
+{
+	GatherMergePath *pathnode = makeNode(GatherMergePath);
+	Cost			 input_startup_cost = 0;
+	Cost			 input_total_cost = 0;
+
+	Assert(subpath->parallel_safe);
+	Assert(pathkeys);
+
+	pathnode->path.pathtype = T_GatherMerge;
+	pathnode->path.parent = rel;
+	pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
+														  required_outer);
+	pathnode->path.parallel_aware = false;
+
+	pathnode->subpath = subpath;
+	pathnode->num_workers = subpath->parallel_workers;
+	pathnode->path.pathkeys = pathkeys;
+	pathnode->path.pathtarget = target ? target : rel->reltarget;
+	pathnode->path.rows += subpath->rows;
+
+	if (pathkeys_contained_in(pathkeys, subpath->pathkeys))
+	{
+		/* Subpath is adequately ordered, we won't need to sort it */
+		input_startup_cost += subpath->startup_cost;
+		input_total_cost += subpath->total_cost;
+	}
+	else
+	{
+		/* We'll need to insert a Sort node, so include cost for that */
+		Path		sort_path;		/* dummy for result of cost_sort */
+
+		cost_sort(&sort_path,
+				  root,
+				  pathkeys,
+				  subpath->total_cost,
+				  subpath->rows,
+				  subpath->pathtarget->width,
+				  0.0,
+				  work_mem,
+				  0 /* FIXME: pathnode->limit_tuples*/);
+		input_startup_cost += sort_path.startup_cost;
+		input_total_cost += sort_path.total_cost;
+	}
+
+	cost_gather_merge(pathnode, root, rel, pathnode->path.param_info,
+					  input_startup_cost, input_total_cost);
+
+	return pathnode;
+}
+
+/*
  * translate_sub_tlist - get subquery column numbers represented by tlist
  *
  * The given targetlist usually contains only Vars referencing the given relid.
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 622279b..502f17d 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -894,6 +894,15 @@ static struct config_bool ConfigureNamesBool[] =
 		true,
 		NULL, NULL, NULL
 	},
+	{
+		{"enable_gathermerge", PGC_USERSET, QUERY_TUNING_METHOD,
+			gettext_noop("Enables the planner's use of gather merge plans."),
+			NULL
+		},
+		&enable_gathermerge,
+		true,
+		NULL, NULL, NULL
+	},

 	{
 		{"geqo", PGC_USERSET, QUERY_TUNING_GEQO,
diff --git a/src/include/executor/nodeGatherMerge.h b/src/include/executor/nodeGatherMerge.h
new file mode 100644
index 0000000..58dcebf
--- /dev/null
+++ b/src/include/executor/nodeGatherMerge.h
@@ -0,0 +1,27 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeGatherMerge.h
+ *		prototypes for nodeGatherMerge.c
+ *
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeGatherMerge.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODEGATHERMERGE_H
+#define NODEGATHERMERGE_H
+
+#include "nodes/execnodes.h"
+
+extern GatherMergeState *ExecInitGatherMerge(GatherMerge * node,
+					EState *estate,
+					int eflags);
+extern TupleTableSlot *ExecGatherMerge(GatherMergeState * node);
+extern void ExecEndGatherMerge(GatherMergeState * node);
+extern void ExecReScanGatherMerge(GatherMergeState * node);
+extern void ExecShutdownGatherMerge(GatherMergeState * node);
+
+#endif   /* NODEGATHERMERGE_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 4fa3661..54d929f 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1963,6 +1963,33 @@ typedef struct GatherState
 } GatherState;

 /* ----------------
+ * GatherMergeState information
+ *
+ *		Gather merge nodes launch 1 or more parallel workers, run a
+ *		subplan in those workers, collect the results and perform sort.
+ * ----------------
+ */
+struct GMReaderTuple;
+
+typedef struct GatherMergeState
+{
+	PlanState	ps;				/* its first field is NodeTag */
+	bool		initialized;
+	struct ParallelExecutorInfo *pei;
+	int			nreaders;
+	int			nworkers_launched;
+	struct TupleQueueReader **reader;
+	TupleTableSlot *funnel_slot;
+	TupleTableSlot **gm_slots;
+	struct binaryheap *gm_heap; /* binary heap of slot indices */
+	bool		gm_initialized; /* gather merge initilized ? */
+	bool		need_to_scan_locally;
+	int			gm_nkeys;
+	SortSupport gm_sortkeys;	/* array of length ms_nkeys */
+	struct GMReaderTuple *gm_tuple;	/* array of lenght nreaders + leader */
+} GatherMergeState;
+
+/* ----------------
  *	 HashState information
  * ----------------
  */
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 88297bb..edfb917 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -75,6 +75,7 @@ typedef enum NodeTag
 	T_WindowAgg,
 	T_Unique,
 	T_Gather,
+	T_GatherMerge,
 	T_Hash,
 	T_SetOp,
 	T_LockRows,
@@ -123,6 +124,7 @@ typedef enum NodeTag
 	T_WindowAggState,
 	T_UniqueState,
 	T_GatherState,
+	T_GatherMergeState,
 	T_HashState,
 	T_SetOpState,
 	T_LockRowsState,
@@ -244,6 +246,7 @@ typedef enum NodeTag
 	T_MaterialPath,
 	T_UniquePath,
 	T_GatherPath,
+	T_GatherMergePath,
 	T_ProjectionPath,
 	T_SortPath,
 	T_GroupPath,
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index e2fbc7d..ec319bf 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -765,6 +765,22 @@ typedef struct Gather
 	bool		invisible;		/* suppress EXPLAIN display (for testing)? */
 } Gather;

+/* ------------
+ *		gather merge node
+ * ------------
+ */
+typedef struct GatherMerge
+{
+	Plan		plan;
+	int			num_workers;
+	/* remaining fields are just like the sort-key info in struct Sort */
+	int			numCols;		/* number of sort-key columns */
+	AttrNumber *sortColIdx;		/* their indexes in the target list */
+	Oid		   *sortOperators;	/* OIDs of operators to sort them by */
+	Oid		   *collations;		/* OIDs of collations */
+	bool	   *nullsFirst;		/* NULLS FIRST/LAST directions */
+} GatherMerge;
+
 /* ----------------
  *		hash build node
  *
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 3a1255a..dfaca79 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -1194,6 +1194,19 @@ typedef struct GatherPath
 } GatherPath;

 /*
+ * GatherMergePath runs several copies of a plan in parallel and
+ * collects the results. FIXME: comments
+ */
+typedef struct GatherMergePath
+{
+	Path		path;
+	Path	   *subpath;		/* path for each worker */
+	int			num_workers;	/* number of workers sought to help */
+	bool		single_copy;	/* path must not be executed >1x */
+} GatherMergePath;
+
+
+/*
  * All join-type paths share these fields.
  */

diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 2a4df2f..cd48cc4 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -66,6 +66,7 @@ extern bool enable_nestloop;
 extern bool enable_material;
 extern bool enable_mergejoin;
 extern bool enable_hashjoin;
+extern bool enable_gathermerge;
 extern int	constraint_exclusion;

 extern double clamp_row_est(double nrows);
@@ -198,5 +199,8 @@ extern Selectivity clause_selectivity(PlannerInfo *root,
 				   int varRelid,
 				   JoinType jointype,
 				   SpecialJoinInfo *sjinfo);
+extern void cost_gather_merge(GatherMergePath *path, PlannerInfo *root,
+							  RelOptInfo *rel, ParamPathInfo *param_info,
+							  Cost input_startup_cost, Cost input_total_cost);

 #endif   /* COST_H */
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 71d9154..3dbe9fc 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -267,5 +267,10 @@ extern ParamPathInfo *get_joinrel_parampathinfo(PlannerInfo *root,
 						  List **restrict_clauses);
 extern ParamPathInfo *get_appendrel_parampathinfo(RelOptInfo *appendrel,
 							Relids required_outer);
+extern GatherMergePath *create_gather_merge_path(PlannerInfo *root,
+												 RelOptInfo *rel, Path *subpath,
+												 PathTarget *target,
+												 List *pathkeys,
+												 Relids required_outer);

 #endif   /* PATHNODE_H */
diff --git a/src/test/regress/expected/rangefuncs.out b/src/test/regress/expected/rangefuncs.out
index f06cfa4..5c547e2 100644
--- a/src/test/regress/expected/rangefuncs.out
+++ b/src/test/regress/expected/rangefuncs.out
@@ -2,6 +2,7 @@ SELECT name, setting FROM pg_settings WHERE name LIKE 'enable%';
          name         | setting 
 ----------------------+---------
  enable_bitmapscan    | on
+ enable_gathermerge   | on
  enable_hashagg       | on
  enable_hashjoin      | on
  enable_indexonlyscan | on
@@ -12,7 +13,7 @@ SELECT name, setting FROM pg_settings WHERE name LIKE 'enable%';
  enable_seqscan       | on
  enable_sort          | on
  enable_tidscan       | on
-(11 rows)
+(12 rows)

 CREATE TABLE foo2(fooid int, f2 int);
 INSERT INTO foo2 VALUES(1, 11);