TABLESAMPLE, SQL Standard and extensible

Add a TABLESAMPLE clause to SELECT statements that allows
user to specify random BERNOULLI sampling or block level
SYSTEM sampling. Implementation allows for extensible
sampling functions to be written, using a standard API.
Basic version follows SQLStandard exactly. Usable
concrete use cases for the sampling API follow in later
commits.

Petr Jelinek

Reviewed by Michael Paquier and Simon Riggs

62 files changed, 2574 insertions, 37 deletions

diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b48f04..bd93a6a8d1e 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  tablesample transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 1a8d2f2d0b5..f0c2394e600 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -80,8 +80,9 @@ bool		synchronize_seqscans = true;
 static HeapScanDesc heap_beginscan_internal(Relation relation,
 						Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap);
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan,
+						bool temp_snap);
 static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup,
 					TransactionId xid, CommandId cid, int options);
 static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf,
@@ -294,9 +295,10 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
 
 	/*
 	 * Currently, we don't have a stats counter for bitmap heap scans (but the
-	 * underlying bitmap index scans will be counted).
+	 * underlying bitmap index scans will be counted) or sample scans (we only
+	 * update stats for tuple fetches there)
 	 */
-	if (!scan->rs_bitmapscan)
+	if (!scan->rs_bitmapscan && !scan->rs_samplescan)
 		pgstat_count_heap_scan(scan->rs_rd);
 }
 
@@ -315,7 +317,7 @@ heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk, BlockNumber numBlks)
  * In page-at-a-time mode it performs additional work, namely determining
  * which tuples on the page are visible.
  */
-static void
+void
 heapgetpage(HeapScanDesc scan, BlockNumber page)
 {
 	Buffer		buffer;
@@ -1310,6 +1312,9 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
  * HeapScanDesc for a bitmap heap scan.  Although that scan technology is
  * really quite unlike a standard seqscan, there is just enough commonality
  * to make it worth using the same data structure.
+ *
+ * heap_beginscan_samplingscan is alternate entry point for setting up a
+ * HeapScanDesc for a TABLESAMPLE scan.
  * ----------------
  */
 HeapScanDesc
@@ -1317,7 +1322,7 @@ heap_beginscan(Relation relation, Snapshot snapshot,
 			   int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, false);
+								   true, true, true, false, false, false);
 }
 
 HeapScanDesc
@@ -1327,7 +1332,7 @@ heap_beginscan_catalog(Relation relation, int nkeys, ScanKey key)
 	Snapshot	snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
 
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, true);
+								   true, true, true, false, false, true);
 }
 
 HeapScanDesc
@@ -1336,7 +1341,8 @@ heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   allow_strat, allow_sync, false, false);
+								   allow_strat, allow_sync, true,
+								   false, false, false);
 }
 
 HeapScanDesc
@@ -1344,14 +1350,24 @@ heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   false, false, true, false);
+								   false, false, true, true, false, false);
+}
+
+HeapScanDesc
+heap_beginscan_sampling(Relation relation, Snapshot snapshot,
+						int nkeys, ScanKey key,
+						bool allow_strat, bool allow_pagemode)
+{
+	return heap_beginscan_internal(relation, snapshot, nkeys, key,
+								   allow_strat, false, allow_pagemode,
+								   false, true, false);
 }
 
 static HeapScanDesc
 heap_beginscan_internal(Relation relation, Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap)
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan, bool temp_snap)
 {
 	HeapScanDesc scan;
 
@@ -1373,6 +1389,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	scan->rs_snapshot = snapshot;
 	scan->rs_nkeys = nkeys;
 	scan->rs_bitmapscan = is_bitmapscan;
+	scan->rs_samplescan = is_samplescan;
 	scan->rs_strategy = NULL;	/* set in initscan */
 	scan->rs_allow_strat = allow_strat;
 	scan->rs_allow_sync = allow_sync;
@@ -1381,7 +1398,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	/*
 	 * we can use page-at-a-time mode if it's an MVCC-safe snapshot
 	 */
-	scan->rs_pageatatime = IsMVCCSnapshot(snapshot);
+	scan->rs_pageatatime = allow_pagemode && IsMVCCSnapshot(snapshot);
 
 	/*
 	 * For a seqscan in a serializable transaction, acquire a predicate lock
diff --git a/src/backend/access/tablesample/Makefile b/src/backend/access/tablesample/Makefile
new file mode 100644
index 00000000000..46eeb59f9c4
--- /dev/null
+++ b/src/backend/access/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/access/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = tablesample.o system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/tablesample/bernoulli.c b/src/backend/access/tablesample/bernoulli.c
new file mode 100644
index 00000000000..c91f3f593e5
--- /dev/null
+++ b/src/backend/access/tablesample/bernoulli.c
@@ -0,0 +1,235 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tablesample.h"
+#include "access/relscan.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+
+/* tsdesc */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* number of blocks */
+	BlockNumber blockno;		/* current block */
+	float4 probability;			/* probabilty that tuple will be returned (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator tsdesc */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	uint32				seed = PG_GETARG_UINT32(1);
+	float4				percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	HeapScanDesc		scan = tsdesc->heapScan;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->startblock = scan->rs_startblock;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->blockno = InvalidBlockNumber;
+	sampler->probability = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	tsdesc->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc		   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData   *sampler =
+		(BernoulliSamplerData *) tsdesc->tsmdata;
+
+	/*
+	 * Bernoulli sampling scans all blocks on the table and supports
+	 * syncscan so loop from startblock to startblock instead of
+	 * from 0 to nblocks.
+	 */
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = sampler->startblock;
+	else
+	{
+		sampler->blockno++;
+
+		if (sampler->blockno >= sampler->nblocks)
+			sampler->blockno = 0;
+
+		if (sampler->blockno == sampler->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * It is ok here to return tuple offset without knowing if tuple is visible
+ * and not check it via examinetuple. The reason for that is that we do the
+ * coinflip (random number generation) for every tuple in the table. Since all
+ * tuples have same probability of being returned the visible and invisible
+ * tuples will be returned in same ratio as they have in the actual table.
+ * This means that there is no skew towards either visible or invisible tuples
+ * and the  number returned visible tuples to from the executor node is the
+ * fraction of visible tuples which was specified in input.
+ *
+ * This is faster than doing the coinflip in the examinetuple because we don't
+ * have to do visibility checks on uninteresting tuples.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc		   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	OffsetNumber			maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData   *sampler =
+		(BernoulliSamplerData *) tsdesc->tsmdata;
+	OffsetNumber			tupoffset = sampler->lt;
+	float4					probability = sampler->probability;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/*
+	 * Loop over tuple offsets until the random generator returns value that
+	 * is within the probability of returning the tuple or until we reach
+	 * end of the block.
+	 *
+	 * (This is our implementation of bernoulli trial)
+	 */
+	while (sampler_random_fract(sampler->randstate) > probability)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+
+	pfree(tsdesc->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset tsdesc (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc		   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData   *sampler =
+		(BernoulliSamplerData *) tsdesc->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/access/tablesample/system.c b/src/backend/access/tablesample/system.c
new file mode 100644
index 00000000000..1412e511faf
--- /dev/null
+++ b/src/backend/access/tablesample/system.c
@@ -0,0 +1,186 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tablesample.h"
+#include "access/relscan.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber nblocks;		/* number of block in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	uint32				seed = PG_GETARG_UINT32(1);
+	float4				percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	HeapScanDesc		scan = tsdesc->heapScan;
+	SystemSamplerData  *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->samplesize = 1 + (int) (sampler->nblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	BlockSampler_Init(&sampler->bs, sampler->nblocks, sampler->samplesize,
+					  sampler->seed);
+
+	tsdesc->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as ANALYZE for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+	BlockNumber			blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	OffsetNumber		maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+	OffsetNumber		tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+
+	pfree(tsdesc->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	BlockSampler_Init(&sampler->bs, sampler->nblocks, sampler->samplesize,
+					  sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*pages = baserel->pages * samplesize;
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/access/tablesample/tablesample.c b/src/backend/access/tablesample/tablesample.c
new file mode 100644
index 00000000000..ef55d062e75
--- /dev/null
+++ b/src/backend/access/tablesample/tablesample.c
@@ -0,0 +1,368 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *        TABLESAMPLE internal API
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *        src/backend/access/tablesample/tablesample.c
+ *
+ * TABLESAMPLE is the SQL standard clause for sampling the relations.
+ *
+ * The API is interface between the Executor and the TABLESAMPLE Methods.
+ *
+ * TABLESAMPLE Methods are implementations of actual sampling algorithms which
+ * can be used for returning a sample of the source relation.
+ * Methods don't read the table directly but are asked for block number and
+ * tuple offset which they want to examine (or return) and the tablesample
+ * interface implemented here does the reading for them.
+ *
+ * We currently only support sampling of the physical relations, but in the
+ * future we might extend the API to support subqueries as well.
+ *
+ * -------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/tablesample.h"
+
+#include "catalog/pg_tablesample_method.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/tqual.h"
+
+
+static bool SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan);
+
+
+/*
+ * Initialize the TABLESAMPLE Descriptor and the TABLESAMPLE Method.
+ */
+TableSampleDesc *
+tablesample_init(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+	TableSampleDesc	*tsdesc = (TableSampleDesc *) palloc0(sizeof(TableSampleDesc));
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(tsdesc->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(tsdesc->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(tsdesc->tsmnexttuple));
+	if (OidIsValid(tablesample->tsmexaminetuple))
+		fmgr_info(tablesample->tsmexaminetuple, &(tsdesc->tsmexaminetuple));
+	else
+		tsdesc->tsmexaminetuple.fn_oid = InvalidOid;
+	fmgr_info(tablesample->tsmreset, &(tsdesc->tsmreset));
+	fmgr_info(tablesample->tsmend, &(tsdesc->tsmend));
+
+	InitFunctionCallInfoData(fcinfo, &tsdesc->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	tsdesc->tupDesc = scanstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
+	tsdesc->heapScan = scanstate->ss.ss_currentScanDesc;
+
+	/* First argument for init function is always TableSampleDesc */
+	fcinfo.arg[0] = PointerGetDatum(tsdesc);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg for init function is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause must be NOT NULL numeric value")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+	/* Rest of the arguments come from user.  */
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+
+	return tsdesc;
+}
+
+/*
+ * Get next tuple from TABLESAMPLE Method.
+ */
+HeapTuple
+tablesample_getnext(TableSampleDesc *desc)
+{
+	HeapScanDesc	scan = desc->heapScan;
+	HeapTuple		tuple = &(scan->rs_ctup);
+	bool			pagemode = scan->rs_pageatatime;
+	BlockNumber		blockno;
+	Page			page;
+	bool			page_all_visible;
+	ItemId			itemid;
+	OffsetNumber	tupoffset,
+					maxoffset;
+
+	if (!scan->rs_inited)
+	{
+		/*
+		 * return null immediately if relation is empty
+		 */
+		if (scan->rs_nblocks == 0)
+		{
+			Assert(!BufferIsValid(scan->rs_cbuf));
+			tuple->t_data = NULL;
+			return NULL;
+		}
+		blockno = DatumGetInt32(FunctionCall1(&desc->tsmnextblock,
+											PointerGetDatum(desc)));
+		if (!BlockNumberIsValid(blockno))
+		{
+			tuple->t_data = NULL;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+		scan->rs_inited = true;
+	}
+	else
+	{
+		/* continue from previously returned page/tuple */
+		blockno = scan->rs_cblock;		/* current page */
+	}
+
+	/*
+	 * When pagemode is disabled, the scan will do visibility checks for each
+	 * tuple it finds so the buffer needs to be locked.
+	 */
+	if (!pagemode)
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+	page = (Page) BufferGetPage(scan->rs_cbuf);
+	page_all_visible = PageIsAllVisible(page);
+	maxoffset = PageGetMaxOffsetNumber(page);
+
+	for (;;)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		tupoffset = DatumGetUInt16(FunctionCall3(&desc->tsmnexttuple,
+											 PointerGetDatum(desc),
+											 UInt32GetDatum(blockno),
+											 UInt16GetDatum(maxoffset)));
+
+		if (OffsetNumberIsValid(tupoffset))
+		{
+			bool	visible;
+			bool	found;
+
+			/* Skip invalid tuple pointers. */
+			itemid = PageGetItemId(page, tupoffset);
+			if (!ItemIdIsNormal(itemid))
+				continue;
+
+			tuple->t_data = (HeapTupleHeader) PageGetItem((Page) page, itemid);
+			tuple->t_len = ItemIdGetLength(itemid);
+			ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
+
+			if (page_all_visible)
+				visible = true;
+			else
+				visible = SampleTupleVisible(tuple, tupoffset, scan);
+
+			/*
+			 * Let the sampling method examine the actual tuple and decide if we
+			 * should return it.
+			 *
+			 * Note that we let it examine even invisible tuples for
+			 * statistical purposes, but not return them since user should
+			 * never see invisible tuples.
+			 */
+			if (OidIsValid(desc->tsmexaminetuple.fn_oid))
+			{
+				found = DatumGetBool(FunctionCall4(&desc->tsmexaminetuple,
+											   PointerGetDatum(desc),
+											   UInt32GetDatum(blockno),
+											   PointerGetDatum(tuple),
+											   BoolGetDatum(visible)));
+				/* Should not happen if sampling method is well written. */
+				if (found && !visible)
+					elog(ERROR, "Sampling method wanted to return invisible tuple");
+			}
+			else
+				found = visible;
+
+			/* Found visible tuple, return it. */
+			if (found)
+			{
+				if (!pagemode)
+					LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+				break;
+			}
+			else
+			{
+				/* Try next tuple from same page. */
+				continue;
+			}
+		}
+
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+
+		blockno = DatumGetInt32(FunctionCall1(&desc->tsmnextblock,
+										  PointerGetDatum(desc)));
+
+		/*
+		 * Report our new scan position for synchronization purposes. We
+		 * don't do that when moving backwards, however. That would just
+		 * mess up any other forward-moving scanners.
+		 *
+		 * Note: we do this before checking for end of scan so that the
+		 * final state of the position hint is back at the start of the
+		 * rel.  That's not strictly necessary, but otherwise when you run
+		 * the same query multiple times the starting position would shift
+		 * a little bit backwards on every invocation, which is confusing.
+		 * We don't guarantee any specific ordering in general, though.
+		 */
+		if (scan->rs_syncscan)
+			ss_report_location(scan->rs_rd, BlockNumberIsValid(blockno) ?
+							   blockno : scan->rs_startblock);
+
+		/*
+		 * Reached end of scan.
+		 */
+		if (!BlockNumberIsValid(blockno))
+		{
+			if (BufferIsValid(scan->rs_cbuf))
+				ReleaseBuffer(scan->rs_cbuf);
+			scan->rs_cbuf = InvalidBuffer;
+			scan->rs_cblock = InvalidBlockNumber;
+			tuple->t_data = NULL;
+			scan->rs_inited = false;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		page = (Page) BufferGetPage(scan->rs_cbuf);
+		page_all_visible = PageIsAllVisible(page);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	pgstat_count_heap_getnext(scan->rs_rd);
+
+	return &(scan->rs_ctup);
+}
+
+/*
+ * Reset the sampling to starting state
+ */
+void
+tablesample_reset(TableSampleDesc *desc)
+{
+	(void) FunctionCall1(&desc->tsmreset, PointerGetDatum(desc));
+}
+
+/*
+ * Signal the sampling method that the scan has finished.
+ */
+void
+tablesample_end(TableSampleDesc *desc)
+{
+	(void) FunctionCall1(&desc->tsmend, PointerGetDatum(desc));
+}
+
+/*
+ * Check visibility of the tuple.
+ */
+static bool
+SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan)
+{
+	/*
+	 * If this scan is reading whole pages at a time, there is already
+	 * visibility info present in rs_vistuples so we can just search it
+	 * for the tupoffset.
+	 */
+	if (scan->rs_pageatatime)
+	{
+		int start = 0,
+			end = scan->rs_ntuples - 1;
+
+		/*
+		 * Do the binary search over rs_vistuples, it's already sorted by
+		 * OffsetNumber so we don't need to do any sorting ourselves here.
+		 *
+		 * We could use bsearch() here but it's slower for integers because
+		 * of the function call overhead and because it needs boiler plate code
+		 * it would not save us anything code-wise anyway.
+		 */
+		while (start <= end)
+		{
+			int mid = start + (end - start) / 2;
+			OffsetNumber curoffset = scan->rs_vistuples[mid];
+
+			if (curoffset == tupoffset)
+				return true;
+			else if (curoffset > tupoffset)
+				end = mid - 1;
+			else
+				start = mid + 1;
+		}
+
+		return false;
+	}
+	else
+	{
+		/* No pagemode, we have to check the tuple itself. */
+		Snapshot	snapshot = scan->rs_snapshot;
+		Buffer		buffer = scan->rs_cbuf;
+
+		bool visible = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer);
+
+		CheckForSerializableConflictOut(visible, scan->rs_rd, tuple, buffer,
+										snapshot);
+
+		return visible;
+	}
+}
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index 37d05d1acc6..3d1139b5ba0 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -40,9 +40,8 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
 	pg_foreign_table.h pg_policy.h pg_replication_origin.h \
-	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
-	pg_transform.h \
-	toasting.h indexing.h \
+	pg_tablesample_method.h pg_default_acl.h pg_seclabel.h pg_shseclabel.h \
+	pg_collation.h pg_range.h pg_transform.h toasting.h indexing.h \
     )
 
 # location of Catalog.pm
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 952cf204a0a..65e329eab07 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1150,7 +1150,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * sampler_random_fract());
+						int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index eeb8f19017e..478771c6ba1 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -731,6 +731,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_ValuesScan:
 		case T_CteScan:
 		case T_WorkTableScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -967,6 +968,21 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			{
+				/*
+				 * Fetch the tablesample method name from RTE.
+				 *
+				 * It would be nice to also show parameters, but since we
+				 * support arbitrary expressions as parameter it might get
+				 * quite messy.
+				 */
+				RangeTblEntry *rte;
+				rte = rt_fetch(((SampleScan *) plan)->scanrelid, es->rtable);
+				custom_name = get_tablesample_method_name(rte->tablesample->tsmid);
+				pname = psprintf("Sample Scan (%s)", custom_name);
+			}
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1089,6 +1105,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (((Scan *) plan)->scanrelid > 0)
 				ExplainScanTarget((Scan *) plan, es);
 			break;
+		case T_SampleScan:
+			ExplainScanTarget((Scan *) plan, es);
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *indexscan = (IndexScan *) plan;
@@ -1339,6 +1358,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2238,6 +2258,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index bc5d373d68a..08cba6fa2b5 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execIndexing.o execJunk.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f03f0..4948a265cb2 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index d87be963a95..bcd287f8742 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499fb7a..03c2febc3e1 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 00000000000..fc89d1dca03
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,256 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/tablesample.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "pgstat.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate,
+							 int eflags, TableSampleClause *tablesample);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	TupleTableSlot	   *slot;
+	TableSampleDesc	   *tsdesc;
+	HeapTuple			tuple;
+
+	/*
+	 * get information from the scan state
+	 */
+	slot = node->ss.ss_ScanTupleSlot;
+	tsdesc = node->tsdesc;
+
+	tuple = tablesample_getnext(tsdesc);
+
+	if (tuple)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   tsdesc->heapScan->rs_cbuf,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags,
+				 TableSampleClause *tablesample)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+
+	/*
+	 * Even though we aren't going to do a conventional seqscan, it is useful
+	 * to create a HeapScanDesc --- many of the fields in it are usable.
+	 */
+	node->ss.ss_currentScanDesc =
+		heap_beginscan_sampling(currentRelation, estate->es_snapshot, 0, NULL,
+								tablesample->tsmseqscan,
+								tablesample->tsmpagemode);
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags, rte->tablesample);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	scanstate->tsdesc = tablesample_init(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished the scan.
+	 */
+	tablesample_end(node->tsdesc);
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close heap scan
+	 */
+	heap_endscan(node->ss.ss_currentScanDesc);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *node)
+{
+	heap_rescan(node->ss.ss_currentScanDesc, NULL);
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	tablesample_reset(node->tsdesc);
+
+	ExecScanReScan(&node->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 25839eed945..bdc7e61935c 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -642,6 +642,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2063,6 +2079,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2224,6 +2241,40 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsmseqscan);
+	COPY_SCALAR_FIELD(tsmpagemode);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmexaminetuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4179,6 +4230,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4842,6 +4896,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_FuncWithArgs:
 			retval = _copyFuncWithArgs(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index c4b3615caf3..d483221fb7a 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2359,6 +2359,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2503,6 +2504,36 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsmseqscan);
+	COMPARE_SCALAR_FIELD(tsmpagemode);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmexaminetuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3236,6 +3267,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_FuncWithArgs:
 			retval = _equalFuncWithArgs(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index eac02159236..42d62d32d93 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -2058,6 +2058,14 @@ range_table_walker(List *rtable,
 		switch (rte->rtekind)
 		{
 			case RTE_RELATION:
+				if (rte->tablesample)
+				{
+					if (walker(rte->tablesample->args, context))
+						return true;
+					if (walker(rte->tablesample->repeatable, context))
+						return true;
+				}
+				break;
 			case RTE_CTE:
 				/* nothing to do */
 				break;
@@ -2813,6 +2821,14 @@ range_table_mutator(List *rtable,
 		switch (rte->rtekind)
 		{
 			case RTE_RELATION:
+				if (rte->tablesample)
+				{
+					MUTATE(rte->tablesample->args, rte->tablesample->args,
+						   List *);
+					MUTATE(rte->tablesample->repeatable,
+						   rte->tablesample->repeatable, Node *);
+				}
+				break;
 			case RTE_CTE:
 				/* we don't bother to copy eref, aliases, etc; OK? */
 				break;
@@ -3309,6 +3325,18 @@ raw_expression_tree_walker(Node *node,
 			break;
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index fe868b889d9..7918553da0a 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -592,6 +592,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -2445,6 +2453,36 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_BOOL_FIELD(tsmseqscan);
+	WRITE_BOOL_FIELD(tsmpagemode);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmexaminetuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2474,6 +2512,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2973,6 +3012,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3319,6 +3361,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 8136306e1e5..c8fb894a75a 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -352,6 +352,46 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_BOOL_FIELD(tsmseqscan);
+	READ_BOOL_FIELD(tsmpagemode);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmexaminetuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1255,6 +1295,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1351,6 +1392,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 9caca94f64b..4cd1bf65e74 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,10 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
+				   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -265,6 +269,11 @@ set_rel_size(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_size(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Sampled relation */
+					set_tablesample_rel_size(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -332,6 +341,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +432,41 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_size
+ *	  Set size estimates for a sampled relation.
+ */
+static void
+set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	/* Mark rel with estimated output rows, width, etc */
+	set_baserel_size_estimates(root, rel);
+}
+
+/*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids	required_outer;
+	Path   *path;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	path = create_samplescan_path(root, rel, required_outer);
+	rel->pathlist = list_make1(path);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 1a0d358c5f7..c2b2b7622a6 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -220,6 +220,73 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we don't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	RangeTblEntry		   *rte = planner_rt_fetch(baserel->relid, root);
+	TableSampleClause	   *tablesample = rte->tablesample;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Mark the path with the correct row estimate */
+	if (path->param_info)
+		path->rows = path->param_info->ppi_rows;
+	else
+		path->rows = baserel->rows;
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(tablesample->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(tablesample->args),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples));
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = tablesample->tsmseqscan ? spc_seq_page_cost :
+					spc_random_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->startup_cost = startup_cost;
+	path->total_cost = startup_cost + run_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 783e34b4fbc..c6095167e80 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -59,6 +59,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -101,6 +103,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig, Oid *indexorderbyops,
@@ -229,6 +232,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -344,6 +348,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -547,6 +558,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1134,6 +1146,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3378,6 +3429,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 8de57c8e6bb..9ba10516bb2 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -60,6 +60,7 @@ planner_hook_type planner_hook = NULL;
 #define EXPRKIND_LIMIT			6
 #define EXPRKIND_APPINFO		7
 #define EXPRKIND_PHV			8
+#define EXPRKIND_TABLESAMPLE    9
 
 /* Passthrough data for standard_qp_callback */
 typedef struct
@@ -486,7 +487,19 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
 		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 		int			kind;
 
-		if (rte->rtekind == RTE_SUBQUERY)
+		if (rte->rtekind == RTE_RELATION)
+		{
+			if (rte->tablesample)
+			{
+				rte->tablesample->args = (List *)
+					preprocess_expression(root, (Node *) rte->tablesample->args,
+										  EXPRKIND_TABLESAMPLE);
+				rte->tablesample->repeatable = (Node *)
+					preprocess_expression(root, rte->tablesample->repeatable,
+										  EXPRKIND_TABLESAMPLE);
+			}
+		}
+		else if (rte->rtekind == RTE_SUBQUERY)
 		{
 			/*
 			 * We don't want to do all preprocessing yet on the subquery's
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 517409d28a0..73b19888369 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -451,6 +451,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index afccee53acf..2f7f5c0df0e 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2167,6 +2167,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index faca30b322d..ea7a47bdf45 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,26 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+Path *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	Path		   *pathnode = makeNode(Path);
+
+	pathnode->pathtype = T_SampleScan;
+	pathnode->parent = rel;
+	pathnode->param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->pathkeys = NIL;	/* samplescan has unordered result */
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1778,6 +1798,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 2dce87879e7..14397830686 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -454,6 +454,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -625,8 +626,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TRANSFORM TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TRANSFORM TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10386,6 +10387,10 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample
+				{
+					$$ = (Node *) $1;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10711,6 +10716,32 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr opt_alias_clause tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $3;
+					n->relation = $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' expr_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' a_expr ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/					{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13804,6 +13835,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 73c505ed85b..6b1bbe57d0e 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -17,6 +17,7 @@
 
 #include "access/heapam.h"
 #include "catalog/catalog.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_constraint.h"
 #include "catalog/pg_type.h"
@@ -31,6 +32,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -39,6 +41,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -419,6 +422,39 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *rv)
+{
+	RangeTblEntry   *rte = NULL;
+	CommonTableExpr *cte = NULL;
+	TableSampleClause *tablesample = NULL;
+
+	/* if relation has an unqualified name, it might be a CTE reference */
+	if (!rv->relation->schemaname)
+	{
+		Index	levelsup;
+		cte = scanNameSpaceForCTE(pstate, rv->relation->relname, &levelsup);
+	}
+
+	/* We first need to build a range table entry */
+	if (!cte)
+		rte = transformTableEntry(pstate, rv->relation);
+
+	if (!rte ||
+		(rte->relkind != RELKIND_RELATION &&
+		rte->relkind != RELKIND_MATVIEW))
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("TABLESAMPLE clause can only be used on tables and materialized views"),
+				 parser_errposition(pstate, rv->relation->location)));
+
+	tablesample = ParseTableSample(pstate, rv->method, rv->repeatable,
+								   rv->args, rv->relation->location);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -1127,6 +1163,26 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index f7affebf84e..fa50f92d8dd 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -767,6 +769,147 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs, int location)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod),
+				 parser_errposition(pstate, location)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsmseqscan = tsm->tsmseqscan;
+	tablesample->tsmpagemode = tsm->tsmpagemode;
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmexaminetuple = tsm->tsmexaminetuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Check user provided expected number of arguments. */
+	if (list_length(sampleargs) != initnargs)
+		ereport(ERROR,
+				(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
+		 errmsg_plural("tablesample method \"%s\" expects %d argument got %d",
+					   "tablesample method \"%s\" expects %d arguments got %d",
+					   initnargs,
+					   samplemethod,
+					   initnargs, list_length(sampleargs)),
+		 parser_errposition(pstate, location)));
+
+	/* Transform the arguments, typecasting them as needed. */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *inarg = (Node *) lfirst(larg);
+		Node   *arg = transformExpr(pstate, inarg, EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		if (argtype != init_arg_types[nargs])
+		{
+			if (!can_coerce_type(1, &argtype, &init_arg_types[nargs],
+								 COERCION_IMPLICIT))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("wrong parameter %d for tablesample method \"%s\"",
+							nargs + 1, samplemethod),
+					 errdetail("Expected type %s got %s.",
+							   format_type_be(init_arg_types[nargs]),
+							   format_type_be(argtype)),
+					 parser_errposition(pstate, exprLocation(inarg))));
+
+			arg = coerce_type(pstate, arg, argtype, init_arg_types[nargs], -1,
+							  COERCION_IMPLICIT, COERCE_IMPLICIT_CAST, -1);
+		}
+
+		fargs = lappend(fargs, arg);
+		nargs++;
+	}
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index 39302a410b8..e27afd1a3e0 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -2209,6 +2209,9 @@ view_query_is_auto_updatable(Query *viewquery, bool check_cols)
 		 base_rte->relkind != RELKIND_VIEW))
 		return gettext_noop("Views that do not select from a single table or view are not automatically updatable.");
 
+	if (base_rte->tablesample)
+		return gettext_noop("Views containing TABLESAMPLE are not automatically updatable.");
+
 	/*
 	 * Check that the view has at least one updatable column. This is required
 	 * for INSERT/UPDATE but not for DELETE.
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 903e80aea35..298eebf5e67 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -32,6 +32,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -345,6 +346,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4220,6 +4223,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8529,6 +8576,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 1dc293297d9..f259751e157 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -32,6 +32,7 @@
 #include "catalog/pg_range.h"
 #include "catalog/pg_statistic.h"
 #include "catalog/pg_transform.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_type.h"
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
@@ -2996,3 +2997,29 @@ get_range_subtype(Oid rangeOid)
 	else
 		return InvalidOid;
 }
+
+/*				---------- PG_TABLESAMPLE_METHOD CACHE ----------			 */
+
+/*
+ * get_tablesample_method_name - given a tablesample method OID,
+ * look up the name or NULL if not found
+ */
+char *
+get_tablesample_method_name(Oid tsmid)
+{
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmid));
+	if (HeapTupleIsValid(tuple))
+	{
+		Form_pg_tablesample_method	tup =
+			(Form_pg_tablesample_method) GETSTRUCT(tuple);
+		char	   *result;
+
+		result = pstrdup(NameStr(tup->tsmname));
+		ReleaseSysCache(tuple);
+		return result;
+	}
+	else
+		return NULL;
+}
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index f58e1cebf2a..7def1be32ae 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -56,6 +56,7 @@
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_replication_origin.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_transform.h"
 #include "catalog/pg_ts_config.h"
@@ -666,6 +667,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
index 1eeabaf1588..9becc63bf82 100644
--- a/src/backend/utils/misc/sampling.c
+++ b/src/backend/utils/misc/sampling.c
@@ -46,6 +46,8 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->n = samplesize;
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
+
+	sampler_random_init_state(randseed, bs->randstate);
 }
 
 bool
@@ -92,7 +94,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract();
+	V = sampler_random_fract(bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -126,8 +128,14 @@ BlockSampler_Next(BlockSampler bs)
 void
 reservoir_init_selection_state(ReservoirState rs, int n)
 {
+	/*
+	 * Reservoir sampling is not used anywhere where it would need to return
+	 * repeatable results so we can initialize it randomly.
+	 */
+	sampler_random_init_state(random(), rs->randstate);
+
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	*rs = exp(-log(sampler_random_fract()) / n);
+	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
 }
 
 double
@@ -142,7 +150,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(); /* Generate V */
+		V = sampler_random_fract(rs->randstate); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -158,7 +166,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 	else
 	{
 		/* Now apply Algorithm Z */
-		double		W = *rs;
+		double		W = rs->W;
 		double		term = t - (double) n + 1;
 
 		for (;;)
@@ -174,7 +182,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract();
+			U = sampler_random_fract(rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -203,11 +211,11 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract(rs->randstate)) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
-		*rs = W;
+		rs->W = W;
 	}
 	return S;
 }
@@ -217,10 +225,17 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  * Random number generator used by sampling
  *----------
  */
+void
+sampler_random_init_state(long seed, SamplerRandomState randstate)
+{
+	randstate[0] = RAND48_SEED_0;
+	randstate[1] = (unsigned short) seed;
+	randstate[2] = (unsigned short) (seed >> 16);
+}
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract()
+sampler_random_fract(SamplerRandomState randstate)
 {
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+	return pg_erand48(randstate);
 }
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 49c8ca4d66e..eec7c95b218 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -114,8 +114,12 @@ extern HeapScanDesc heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync);
 extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key);
+extern HeapScanDesc heap_beginscan_sampling(Relation relation,
+						Snapshot snapshot, int nkeys, ScanKey key,
+						bool allow_strat, bool allow_pagemode);
 extern void heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk,
 		   BlockNumber endBlk);
+extern void heapgetpage(HeapScanDesc scan, BlockNumber page);
 extern void heap_rescan(HeapScanDesc scan, ScanKey key);
 extern void heap_endscan(HeapScanDesc scan);
 extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 5a0d724aca5..1b9b2993957 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -29,6 +29,7 @@ typedef struct HeapScanDescData
 	int			rs_nkeys;		/* number of scan keys */
 	ScanKey		rs_key;			/* array of scan key descriptors */
 	bool		rs_bitmapscan;	/* true if this is really a bitmap scan */
+	bool		rs_samplescan;	/* true if this is really a sample scan */
 	bool		rs_pageatatime; /* verify visibility page-at-a-time? */
 	bool		rs_allow_strat; /* allow or disallow use of access strategy */
 	bool		rs_allow_sync;	/* allow or disallow use of syncscan */
diff --git a/src/include/access/tablesample.h b/src/include/access/tablesample.h
new file mode 100644
index 00000000000..222fa8d5561
--- /dev/null
+++ b/src/include/access/tablesample.h
@@ -0,0 +1,60 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.h
+ *        Public header file for TABLESAMPLE clause interface
+ *
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/tablesample.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+#include "access/relscan.h"
+#include "executor/executor.h"
+
+typedef struct TableSampleDesc {
+	HeapScanDesc	heapScan;
+	TupleDesc		tupDesc;	/* Mostly useful for tsmexaminetuple */
+
+	void		   *tsmdata;	/* private method data */
+
+	/* These point to he function of the TABLESAMPLE Method. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmexaminetuple;
+	FmgrInfo		tsmreset;
+	FmgrInfo		tsmend;
+} TableSampleDesc;
+
+
+extern TableSampleDesc *tablesample_init(SampleScanState *scanstate,
+										 TableSampleClause *tablesample);
+extern HeapTuple tablesample_getnext(TableSampleDesc *desc);
+extern void tablesample_reset(TableSampleDesc *desc);
+extern void tablesample_end(TableSampleDesc *desc);
+extern HeapTuple tablesample_source_getnext(TableSampleDesc *desc);
+extern HeapTuple tablesample_source_gettup(TableSampleDesc *desc, ItemPointer tid,
+										   bool *visible);
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+
+#endif
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index 71e0010a6f8..f20567ed5f5 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -316,6 +316,11 @@ DECLARE_UNIQUE_INDEX(pg_replication_origin_roiident_index, 6001, on pg_replicati
 DECLARE_UNIQUE_INDEX(pg_replication_origin_roname_index, 6002, on pg_replication_origin using btree(roname varchar_pattern_ops));
 #define ReplicationOriginNameIndex 6002
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3331, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3331
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3332, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3332
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 1c9edbc3b37..c2185bd9add 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5297,6 +5297,33 @@ DESCR("get an individual replication origin's replication progress");
 DATA(insert OID = 6014 ( pg_show_replication_origin_status PGNSP PGUID 12 1 100 0 0 f f f f f t v 0 0 2249 "" "{26,25,3220,3220}" "{o,o,o,o}" "{local_id, external_id, remote_lsn, local_lsn}" _null_ _null_ pg_show_replication_origin_status _null_ _null_ _null_ ));
 DESCR("get progress for all replication origins");
 
+/* tablesample */
+DATA(insert OID = 3335 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	_null_ tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3336 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_ _null_ tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3337 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	_null_ tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3338 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_ _null_ tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3339 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_ _null_ tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3340 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_ _null_ tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3341 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	_null_ tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3342 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3343 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	_null_ tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3344 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3345 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3346 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_ _null_ tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
+
 /*
  * Symbolic values for provolatile column: these indicate whether the result
  * of a function is dependent *only* on the values of its explicit arguments,
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 00000000000..968d1e696ab
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,78 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+#include "catalog/objectaddress.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3330
+
+CATALOG(pg_tablesample_method,3330)
+{
+	NameData	tsmname;		/* tablesample method name */
+	bool		tsmseqscan;		/* does this method scan whole table sequentially? */
+	bool		tsmpagemode;	/* does this method scan page at a time? */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmexaminetuple;	/* optional function which can examine tuple contents and
+								   decide if tuple should be returned or not */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method					10
+#define Anum_pg_tablesample_method_tsmname			1
+#define Anum_pg_tablesample_method_tsmseqscan		2
+#define Anum_pg_tablesample_method_tsmpagemode		3
+#define Anum_pg_tablesample_method_tsminit			4
+#define Anum_pg_tablesample_method_tsmnextblock		5
+#define Anum_pg_tablesample_method_tsmnexttuple		6
+#define Anum_pg_tablesample_method_tsmexaminetuple	7
+#define Anum_pg_tablesample_method_tsmend			8
+#define Anum_pg_tablesample_method_tsmreset			9
+#define Anum_pg_tablesample_method_tsmcost			10
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3333 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3334 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 00000000000..4b769daec8b
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index fcfe1107f92..972368019a9 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1238,6 +1238,15 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState	ss;
+	struct TableSampleDesc *tsdesc;
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 768f413a451..8b275f6e263 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -419,6 +421,8 @@ typedef enum NodeTag
 	T_OnConflictClause,
 	T_CommonTableExpr,
 	T_RoleSpec,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 053f1b01213..6723f46f3f1 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -336,6 +336,26 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	bool		tsmseqscan;
+	bool		tsmpagemode;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmexaminetuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -536,6 +556,22 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * SQL Standard specifies only one parameter which is percentage. But we allow
+ * custom tablesample methods which may need different input arguments so we
+ * accept list of arguments.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -772,6 +808,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 65f71d81705..4e655b0e6c1 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -287,6 +287,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b15aa..24003ae3591 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0eb3ea..89c8deda95c 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+									Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index faea99108c4..7d5f857ae59 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -368,6 +368,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 32646918e20..40c007c35fc 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,11 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args,
+										   int location);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/port.h b/src/include/port.h
index 3787cbfb761..71113c03944 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -357,6 +357,10 @@ extern off_t ftello(FILE *stream);
 #endif
 #endif
 
+#define RAND48_SEED_0	(0x330e)
+#define RAND48_SEED_1	(0xabcd)
+#define RAND48_SEED_2	(0x1234)
+
 extern double pg_erand48(unsigned short xseed[3]);
 extern long pg_lrand48(void);
 extern void pg_srand48(long seed);
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index ffbaa61e5e2..e2e5734ea7b 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -156,6 +156,7 @@ extern void free_attstatsslot(Oid atttype,
 extern char *get_namespace_name(Oid nspid);
 extern char *get_namespace_name_or_temp(Oid nspid);
 extern Oid	get_range_subtype(Oid rangeOid);
+extern char *get_tablesample_method_name(Oid tsmid);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 9e17d87413d..fd40366bcda 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index e3e7f9cf6ae..4ac208dc364 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -15,7 +15,12 @@
 
 #include "storage/bufmgr.h"
 
-extern double sampler_random_fract(void);
+/* Random generator for sampling code */
+typedef unsigned short SamplerRandomState[3];
+
+extern void sampler_random_init_state(long seed,
+									  SamplerRandomState randstate);
+extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 /* Data structure for Algorithm S from Knuth 3.4.2 */
@@ -25,6 +30,7 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
+	SamplerRandomState randstate; /* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
@@ -35,7 +41,12 @@ extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
 /* Reservoid sampling methods */
-typedef double ReservoirStateData;
+typedef struct
+{
+	double	W;
+	SamplerRandomState randstate; /* random generator state */
+} ReservoirStateData;
+
 typedef ReservoirStateData *ReservoirState;
 
 extern void reservoir_init_selection_state(ReservoirState rs, int n);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index 6634099cbe2..2dbd38488b6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -81,6 +81,8 @@ enum SysCacheIdentifier
 	REPLORIGNAME,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TRFOID,
 	TRFTYPELANG,
diff --git a/src/port/erand48.c b/src/port/erand48.c
index 9d471197c35..12efd8193c4 100644
--- a/src/port/erand48.c
+++ b/src/port/erand48.c
@@ -33,9 +33,6 @@
 
 #include <math.h>
 
-#define RAND48_SEED_0	(0x330e)
-#define RAND48_SEED_1	(0xabcd)
-#define RAND48_SEED_2	(0x1234)
 #define RAND48_MULT_0	(0xe66d)
 #define RAND48_MULT_1	(0xdeec)
 #define RAND48_MULT_2	(0x0005)
diff --git a/src/test/regress/expected/rowsecurity.out b/src/test/regress/expected/rowsecurity.out
index 82bc47895a8..0ae555783bd 100644
--- a/src/test/regress/expected/rowsecurity.out
+++ b/src/test/regress/expected/rowsecurity.out
@@ -101,6 +101,17 @@ NOTICE:  f_leak => great manga
   44 |   8 |      1 | rls_regress_user2 | great manga           | manga
 (4 rows)
 
+SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
+NOTICE:  f_leak => my first novel
+NOTICE:  f_leak => my first manga
+NOTICE:  f_leak => great science fiction
+ did | cid | dlevel |      dauthor      |        dtitle         
+-----+-----+--------+-------------------+-----------------------
+   1 |  11 |      1 | rls_regress_user1 | my first novel
+   4 |  44 |      1 | rls_regress_user1 | my first manga
+   6 |  22 |      1 | rls_regress_user2 | great science fiction
+(3 rows)
+
 -- viewpoint from rls_regress_user2
 SET SESSION AUTHORIZATION rls_regress_user2;
 SELECT * FROM document WHERE f_leak(dtitle) ORDER BY did;
@@ -145,6 +156,21 @@ NOTICE:  f_leak => great manga
   44 |   8 |      1 | rls_regress_user2 | great manga           | manga
 (8 rows)
 
+SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
+NOTICE:  f_leak => my first novel
+NOTICE:  f_leak => my second novel
+NOTICE:  f_leak => my first manga
+NOTICE:  f_leak => great science fiction
+NOTICE:  f_leak => great technology book
+ did | cid | dlevel |      dauthor      |        dtitle         
+-----+-----+--------+-------------------+-----------------------
+   1 |  11 |      1 | rls_regress_user1 | my first novel
+   2 |  11 |      2 | rls_regress_user1 | my second novel
+   4 |  44 |      1 | rls_regress_user1 | my first manga
+   6 |  22 |      1 | rls_regress_user2 | great science fiction
+   7 |  33 |      2 | rls_regress_user2 | great technology book
+(5 rows)
+
 EXPLAIN (COSTS OFF) SELECT * FROM document WHERE f_leak(dtitle);
                         QUERY PLAN                        
 ----------------------------------------------------------
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index eb0bc88ef1f..14acd16da3b 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -128,6 +128,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_transform|t
 pg_trigger|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 00000000000..04e5eb8b807
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,231 @@
+CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+CLOSE tablesample_cur;
+END;
+EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+                                  QUERY PLAN                                   
+-------------------------------------------------------------------------------
+ Sample Scan (system) on test_tablesample  (cost=0.00..26.35 rows=635 width=4)
+(1 row)
+
+EXPLAIN SELECT * FROM test_tablesample_v1;
+                                  QUERY PLAN                                   
+-------------------------------------------------------------------------------
+ Sample Scan (system) on test_tablesample  (cost=0.00..10.54 rows=254 width=4)
+(1 row)
+
+-- errors
+SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
+ERROR:  tablesample method "foobar" does not exist
+LINE 1: SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
+                       ^
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
+ERROR:  REPEATABLE clause must be NOT NULL numeric value
+LINE 1: ... test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
+                                                                 ^
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (-1);
+ERROR:  invalid sample size
+HINT:  Sample size must be numeric value between 0 and 100 (inclusive).
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (200);
+ERROR:  invalid sample size
+HINT:  Sample size must be numeric value between 0 and 100 (inclusive).
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (-1);
+ERROR:  invalid sample size
+HINT:  Sample size must be numeric value between 0 and 100 (inclusive).
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (200);
+ERROR:  invalid sample size
+HINT:  Sample size must be numeric value between 0 and 100 (inclusive).
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+ERROR:  TABLESAMPLE clause can only be used on tables and materialized views
+LINE 1: SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1)...
+                       ^
+INSERT INTO test_tablesample_v1 VALUES(1);
+ERROR:  cannot insert into view "test_tablesample_v1"
+DETAIL:  Views containing TABLESAMPLE are not automatically updatable.
+HINT:  To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.
+WITH query_select AS (SELECT * FROM test_tablesample)
+SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ERROR:  TABLESAMPLE clause can only be used on tables and materialized views
+LINE 2: SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEA...
+                      ^
+SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
+ERROR:  syntax error at or near "TABLESAMPLE"
+LINE 1: ...CT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPL...
+                                                             ^
+-- catalog sanity
+SELECT *
+FROM pg_tablesample_method
+WHERE tsminit IS NULL
+   OR tsmseqscan IS NULL
+   OR tsmpagemode IS NULL
+   OR tsmnextblock IS NULL
+   OR tsmnexttuple IS NULL
+   OR tsmend IS NULL
+   OR tsmreset IS NULL
+   OR tsmcost IS NULL;
+ tsmname | tsmseqscan | tsmpagemode | tsminit | tsmnextblock | tsmnexttuple | tsmexaminetuple | tsmend | tsmreset | tsmcost 
+---------+------------+-------------+---------+--------------+--------------+-----------------+--------+----------+---------
+(0 rows)
+
+-- done
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index b0ebb6b3f4c..f39b73abc2a 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -84,7 +84,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 8409c0f3ef2..9441b97e3a6 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -154,3 +154,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/rowsecurity.sql b/src/test/regress/sql/rowsecurity.sql
index e8c5932b201..fdadf99fd62 100644
--- a/src/test/regress/sql/rowsecurity.sql
+++ b/src/test/regress/sql/rowsecurity.sql
@@ -94,11 +94,15 @@ SET row_security TO ON;
 SELECT * FROM document WHERE f_leak(dtitle) ORDER BY did;
 SELECT * FROM document NATURAL JOIN category WHERE f_leak(dtitle) ORDER BY did;
 
+SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
+
 -- viewpoint from rls_regress_user2
 SET SESSION AUTHORIZATION rls_regress_user2;
 SELECT * FROM document WHERE f_leak(dtitle) ORDER BY did;
 SELECT * FROM document NATURAL JOIN category WHERE f_leak(dtitle) ORDER BY did;
 
+SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
+
 EXPLAIN (COSTS OFF) SELECT * FROM document WHERE f_leak(dtitle);
 EXPLAIN (COSTS OFF) SELECT * FROM document NATURAL JOIN category WHERE f_leak(dtitle);
 
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 00000000000..7b3eb9bedf7
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,74 @@
+CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+CLOSE tablesample_cur;
+END;
+
+EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+EXPLAIN SELECT * FROM test_tablesample_v1;
+
+-- errors
+SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (-1);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (200);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (-1);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (200);
+
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+INSERT INTO test_tablesample_v1 VALUES(1);
+
+WITH query_select AS (SELECT * FROM test_tablesample)
+SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
+
+-- catalog sanity
+
+SELECT *
+FROM pg_tablesample_method
+WHERE tsminit IS NULL
+   OR tsmseqscan IS NULL
+   OR tsmpagemode IS NULL
+   OR tsmnextblock IS NULL
+   OR tsmnexttuple IS NULL
+   OR tsmend IS NULL
+   OR tsmreset IS NULL
+   OR tsmcost IS NULL;
+
+-- done
+DROP TABLE test_tablesample CASCADE;