20 files changed, 284 insertions, 3 deletions
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,