Adding upstream version 13.4.upstream/13.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

7 files changed, 504 insertions, 0 deletions

diff --git a/contrib/tsm_system_rows/.gitignore b/contrib/tsm_system_rows/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/contrib/tsm_system_rows/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/contrib/tsm_system_rows/Makefile b/contrib/tsm_system_rows/Makefile
new file mode 100644
index 0000000..3192ed5
--- /dev/null
+++ b/contrib/tsm_system_rows/Makefile
@@ -0,0 +1,23 @@
+# contrib/tsm_system_rows/Makefile
+
+MODULE_big = tsm_system_rows
+OBJS = \
+	$(WIN32RES) \
+	tsm_system_rows.o
+PGFILEDESC = "tsm_system_rows - TABLESAMPLE method which accepts number of rows as a limit"
+
+EXTENSION = tsm_system_rows
+DATA = tsm_system_rows--1.0.sql
+
+REGRESS = tsm_system_rows
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/tsm_system_rows
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/tsm_system_rows/expected/tsm_system_rows.out b/contrib/tsm_system_rows/expected/tsm_system_rows.out
new file mode 100644
index 0000000..87b4a8f
--- /dev/null
+++ b/contrib/tsm_system_rows/expected/tsm_system_rows.out
@@ -0,0 +1,83 @@
+CREATE EXTENSION tsm_system_rows;
+CREATE TABLE test_tablesample (id int, name text);
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000)
+  FROM generate_series(0, 30) s(i);
+ANALYZE test_tablesample;
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (0);
+ count 
+-------
+     0
+(1 row)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (1);
+ count 
+-------
+     1
+(1 row)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (10);
+ count 
+-------
+    10
+(1 row)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (100);
+ count 
+-------
+    31
+(1 row)
+
+-- bad parameters should get through planning, but not execution:
+EXPLAIN (COSTS OFF)
+SELECT id FROM test_tablesample TABLESAMPLE system_rows (-1);
+               QUERY PLAN               
+----------------------------------------
+ Sample Scan on test_tablesample
+   Sampling: system_rows ('-1'::bigint)
+(2 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE system_rows (-1);
+ERROR:  sample size must not be negative
+-- fail, this method is not repeatable:
+SELECT * FROM test_tablesample TABLESAMPLE system_rows (10) REPEATABLE (0);
+ERROR:  tablesample method system_rows does not support REPEATABLE
+LINE 1: SELECT * FROM test_tablesample TABLESAMPLE system_rows (10) ...
+                                                   ^
+-- but a join should be allowed:
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+  (VALUES (0),(10),(100)) v(nrows),
+  LATERAL (SELECT count(*) FROM test_tablesample
+           TABLESAMPLE system_rows (nrows)) ss;
+                        QUERY PLAN                        
+----------------------------------------------------------
+ Nested Loop
+   ->  Values Scan on "*VALUES*"
+   ->  Aggregate
+         ->  Sample Scan on test_tablesample
+               Sampling: system_rows ("*VALUES*".column1)
+(5 rows)
+
+SELECT * FROM
+  (VALUES (0),(10),(100)) v(nrows),
+  LATERAL (SELECT count(*) FROM test_tablesample
+           TABLESAMPLE system_rows (nrows)) ss;
+ nrows | count 
+-------+-------
+     0 |     0
+    10 |    10
+   100 |    31
+(3 rows)
+
+CREATE VIEW vv AS
+  SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (20);
+SELECT * FROM vv;
+ count 
+-------
+    20
+(1 row)
+
+DROP EXTENSION tsm_system_rows;  -- fail, view depends on extension
+ERROR:  cannot drop extension tsm_system_rows because other objects depend on it
+DETAIL:  view vv depends on function system_rows(internal)
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
diff --git a/contrib/tsm_system_rows/sql/tsm_system_rows.sql b/contrib/tsm_system_rows/sql/tsm_system_rows.sql
new file mode 100644
index 0000000..e3ab420
--- /dev/null
+++ b/contrib/tsm_system_rows/sql/tsm_system_rows.sql
@@ -0,0 +1,39 @@
+CREATE EXTENSION tsm_system_rows;
+
+CREATE TABLE test_tablesample (id int, name text);
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000)
+  FROM generate_series(0, 30) s(i);
+ANALYZE test_tablesample;
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (0);
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (1);
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (10);
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (100);
+
+-- bad parameters should get through planning, but not execution:
+EXPLAIN (COSTS OFF)
+SELECT id FROM test_tablesample TABLESAMPLE system_rows (-1);
+
+SELECT id FROM test_tablesample TABLESAMPLE system_rows (-1);
+
+-- fail, this method is not repeatable:
+SELECT * FROM test_tablesample TABLESAMPLE system_rows (10) REPEATABLE (0);
+
+-- but a join should be allowed:
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+  (VALUES (0),(10),(100)) v(nrows),
+  LATERAL (SELECT count(*) FROM test_tablesample
+           TABLESAMPLE system_rows (nrows)) ss;
+
+SELECT * FROM
+  (VALUES (0),(10),(100)) v(nrows),
+  LATERAL (SELECT count(*) FROM test_tablesample
+           TABLESAMPLE system_rows (nrows)) ss;
+
+CREATE VIEW vv AS
+  SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (20);
+
+SELECT * FROM vv;
+
+DROP EXTENSION tsm_system_rows;  -- fail, view depends on extension
diff --git a/contrib/tsm_system_rows/tsm_system_rows--1.0.sql b/contrib/tsm_system_rows/tsm_system_rows--1.0.sql
new file mode 100644
index 0000000..de508ed
--- /dev/null
+++ b/contrib/tsm_system_rows/tsm_system_rows--1.0.sql
@@ -0,0 +1,9 @@
+/* contrib/tsm_system_rows/tsm_system_rows--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_system_rows" to load this file. \quit
+
+CREATE FUNCTION system_rows(internal)
+RETURNS tsm_handler
+AS 'MODULE_PATHNAME', 'tsm_system_rows_handler'
+LANGUAGE C STRICT;
diff --git a/contrib/tsm_system_rows/tsm_system_rows.c b/contrib/tsm_system_rows/tsm_system_rows.c
new file mode 100644
index 0000000..8bf0b20
--- /dev/null
+++ b/contrib/tsm_system_rows/tsm_system_rows.c
@@ -0,0 +1,340 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_system_rows.c
+ *	  support routines for SYSTEM_ROWS tablesample method
+ *
+ * The desire here is to produce a random sample with a given number of rows
+ * (or the whole relation, if that is fewer rows).  We use a block-sampling
+ * approach.  To ensure that the whole relation will be visited if necessary,
+ * we start at a randomly chosen block and then advance with a stride that
+ * is randomly chosen but is relatively prime to the relation's nblocks.
+ *
+ * Because of the dependence on nblocks, this method cannot be repeatable
+ * across queries.  (Even if the user hasn't explicitly changed the relation,
+ * maintenance activities such as autovacuum might change nblocks.)  However,
+ * we can at least make it repeatable across scans, by determining the
+ * sampling pattern only once on the first scan.  This means that rescans
+ * won't visit blocks added after the first scan, but that is fine since
+ * such blocks shouldn't contain any visible tuples anyway.
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  contrib/tsm_system_rows/tsm_system_rows.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "access/tsmapi.h"
+#include "catalog/pg_type.h"
+#include "miscadmin.h"
+#include "optimizer/optimizer.h"
+#include "utils/sampling.h"
+
+PG_MODULE_MAGIC;
+
+PG_FUNCTION_INFO_V1(tsm_system_rows_handler);
+
+
+/* Private state */
+typedef struct
+{
+	uint32		seed;			/* random seed */
+	int64		ntuples;		/* number of tuples to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	BlockNumber doneblocks;		/* number of already-scanned blocks */
+	BlockNumber lb;				/* last block visited */
+	/* these three values are not changed during a rescan: */
+	BlockNumber nblocks;		/* number of blocks in relation */
+	BlockNumber firstblock;		/* first block to sample from */
+	BlockNumber step;			/* step size, or 0 if not set yet */
+} SystemRowsSamplerData;
+
+static void system_rows_samplescangetsamplesize(PlannerInfo *root,
+												RelOptInfo *baserel,
+												List *paramexprs,
+												BlockNumber *pages,
+												double *tuples);
+static void system_rows_initsamplescan(SampleScanState *node,
+									   int eflags);
+static void system_rows_beginsamplescan(SampleScanState *node,
+										Datum *params,
+										int nparams,
+										uint32 seed);
+static BlockNumber system_rows_nextsampleblock(SampleScanState *node, BlockNumber nblocks);
+static OffsetNumber system_rows_nextsampletuple(SampleScanState *node,
+												BlockNumber blockno,
+												OffsetNumber maxoffset);
+static uint32 random_relative_prime(uint32 n, SamplerRandomState randstate);
+
+
+/*
+ * Create a TsmRoutine descriptor for the SYSTEM_ROWS method.
+ */
+Datum
+tsm_system_rows_handler(PG_FUNCTION_ARGS)
+{
+	TsmRoutine *tsm = makeNode(TsmRoutine);
+
+	tsm->parameterTypes = list_make1_oid(INT8OID);
+
+	/* See notes at head of file */
+	tsm->repeatable_across_queries = false;
+	tsm->repeatable_across_scans = true;
+
+	tsm->SampleScanGetSampleSize = system_rows_samplescangetsamplesize;
+	tsm->InitSampleScan = system_rows_initsamplescan;
+	tsm->BeginSampleScan = system_rows_beginsamplescan;
+	tsm->NextSampleBlock = system_rows_nextsampleblock;
+	tsm->NextSampleTuple = system_rows_nextsampletuple;
+	tsm->EndSampleScan = NULL;
+
+	PG_RETURN_POINTER(tsm);
+}
+
+/*
+ * Sample size estimation.
+ */
+static void
+system_rows_samplescangetsamplesize(PlannerInfo *root,
+									RelOptInfo *baserel,
+									List *paramexprs,
+									BlockNumber *pages,
+									double *tuples)
+{
+	Node	   *limitnode;
+	int64		ntuples;
+	double		npages;
+
+	/* Try to extract an estimate for the limit rowcount */
+	limitnode = (Node *) linitial(paramexprs);
+	limitnode = estimate_expression_value(root, limitnode);
+
+	if (IsA(limitnode, Const) &&
+		!((Const *) limitnode)->constisnull)
+	{
+		ntuples = DatumGetInt64(((Const *) limitnode)->constvalue);
+		if (ntuples < 0)
+		{
+			/* Default ntuples if the value is bogus */
+			ntuples = 1000;
+		}
+	}
+	else
+	{
+		/* Default ntuples if we didn't obtain a non-null Const */
+		ntuples = 1000;
+	}
+
+	/* Clamp to the estimated relation size */
+	if (ntuples > baserel->tuples)
+		ntuples = (int64) baserel->tuples;
+	ntuples = clamp_row_est(ntuples);
+
+	if (baserel->tuples > 0 && baserel->pages > 0)
+	{
+		/* Estimate number of pages visited based on tuple density */
+		double		density = baserel->tuples / (double) baserel->pages;
+
+		npages = ntuples / density;
+	}
+	else
+	{
+		/* For lack of data, assume one tuple per page */
+		npages = ntuples;
+	}
+
+	/* Clamp to sane value */
+	npages = clamp_row_est(Min((double) baserel->pages, npages));
+
+	*pages = npages;
+	*tuples = ntuples;
+}
+
+/*
+ * Initialize during executor setup.
+ */
+static void
+system_rows_initsamplescan(SampleScanState *node, int eflags)
+{
+	node->tsm_state = palloc0(sizeof(SystemRowsSamplerData));
+	/* Note the above leaves tsm_state->step equal to zero */
+}
+
+/*
+ * Examine parameters and prepare for a sample scan.
+ */
+static void
+system_rows_beginsamplescan(SampleScanState *node,
+							Datum *params,
+							int nparams,
+							uint32 seed)
+{
+	SystemRowsSamplerData *sampler = (SystemRowsSamplerData *) node->tsm_state;
+	int64		ntuples = DatumGetInt64(params[0]);
+
+	if (ntuples < 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
+				 errmsg("sample size must not be negative")));
+
+	sampler->seed = seed;
+	sampler->ntuples = ntuples;
+	sampler->lt = InvalidOffsetNumber;
+	sampler->doneblocks = 0;
+	/* lb will be initialized during first NextSampleBlock call */
+	/* we intentionally do not change nblocks/firstblock/step here */
+
+	/*
+	 * We *must* use pagemode visibility checking in this module, so force
+	 * that even though it's currently default.
+	 */
+	node->use_pagemode = true;
+}
+
+/*
+ * Select next block to sample.
+ *
+ * Uses linear probing algorithm for picking next block.
+ */
+static BlockNumber
+system_rows_nextsampleblock(SampleScanState *node, BlockNumber nblocks)
+{
+	SystemRowsSamplerData *sampler = (SystemRowsSamplerData *) node->tsm_state;
+
+	/* First call within scan? */
+	if (sampler->doneblocks == 0)
+	{
+		/* First scan within query? */
+		if (sampler->step == 0)
+		{
+			/* Initialize now that we have scan descriptor */
+			SamplerRandomState randstate;
+
+			/* If relation is empty, there's nothing to scan */
+			if (nblocks == 0)
+				return InvalidBlockNumber;
+
+			/* We only need an RNG during this setup step */
+			sampler_random_init_state(sampler->seed, randstate);
+
+			/* Compute nblocks/firstblock/step only once per query */
+			sampler->nblocks = nblocks;
+
+			/* Choose random starting block within the relation */
+			/* (Actually this is the predecessor of the first block visited) */
+			sampler->firstblock = sampler_random_fract(randstate) *
+				sampler->nblocks;
+
+			/* Find relative prime as step size for linear probing */
+			sampler->step = random_relative_prime(sampler->nblocks, randstate);
+		}
+
+		/* Reinitialize lb */
+		sampler->lb = sampler->firstblock;
+	}
+
+	/* If we've read all blocks or returned all needed tuples, we're done */
+	if (++sampler->doneblocks > sampler->nblocks ||
+		node->donetuples >= sampler->ntuples)
+		return InvalidBlockNumber;
+
+	/*
+	 * It's probably impossible for scan->rs_nblocks to decrease between scans
+	 * within a query; but just in case, loop until we select a block number
+	 * less than scan->rs_nblocks.  We don't care if scan->rs_nblocks has
+	 * increased since the first scan.
+	 */
+	do
+	{
+		/* Advance lb, using uint64 arithmetic to forestall overflow */
+		sampler->lb = ((uint64) sampler->lb + sampler->step) % sampler->nblocks;
+	} while (sampler->lb >= nblocks);
+
+	return sampler->lb;
+}
+
+/*
+ * Select next sampled tuple in current block.
+ *
+ * In block sampling, we just want to sample all the tuples in each selected
+ * block.
+ *
+ * When we reach end of the block, return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+static OffsetNumber
+system_rows_nextsampletuple(SampleScanState *node,
+							BlockNumber blockno,
+							OffsetNumber maxoffset)
+{
+	SystemRowsSamplerData *sampler = (SystemRowsSamplerData *) node->tsm_state;
+	OffsetNumber tupoffset = sampler->lt;
+
+	/* Quit if we've returned all needed tuples */
+	if (node->donetuples >= sampler->ntuples)
+		return InvalidOffsetNumber;
+
+	/* Advance to next possible offset on page */
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/* Done? */
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	return tupoffset;
+}
+
+/*
+ * Compute greatest common divisor of two uint32's.
+ */
+static uint32
+gcd(uint32 a, uint32 b)
+{
+	uint32		c;
+
+	while (a != 0)
+	{
+		c = a;
+		a = b % a;
+		b = c;
+	}
+
+	return b;
+}
+
+/*
+ * Pick a random value less than and relatively prime to n, if possible
+ * (else return 1).
+ */
+static uint32
+random_relative_prime(uint32 n, SamplerRandomState randstate)
+{
+	uint32		r;
+
+	/* Safety check to avoid infinite loop or zero result for small n. */
+	if (n <= 1)
+		return 1;
+
+	/*
+	 * This should only take 2 or 3 iterations as the probability of 2 numbers
+	 * being relatively prime is ~61%; but just in case, we'll include a
+	 * CHECK_FOR_INTERRUPTS in the loop.
+	 */
+	do
+	{
+		CHECK_FOR_INTERRUPTS();
+		r = (uint32) (sampler_random_fract(randstate) * n);
+	} while (r == 0 || gcd(r, n) > 1);
+
+	return r;
+}
diff --git a/contrib/tsm_system_rows/tsm_system_rows.control b/contrib/tsm_system_rows/tsm_system_rows.control
new file mode 100644
index 0000000..b495fb1
--- /dev/null
+++ b/contrib/tsm_system_rows/tsm_system_rows.control
@@ -0,0 +1,6 @@
+# tsm_system_rows extension
+comment = 'TABLESAMPLE method which accepts number of rows as a limit'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_system_rows'
+relocatable = true
+trusted = true