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-rw-r--r--contrib/tsm_system_time/.gitignore4
-rw-r--r--contrib/tsm_system_time/Makefile25
-rw-r--r--contrib/tsm_system_time/expected/tsm_system_time.out100
-rw-r--r--contrib/tsm_system_time/sql/tsm_system_time.sql51
-rw-r--r--contrib/tsm_system_time/tsm_system_time--1.0.sql9
-rw-r--r--contrib/tsm_system_time/tsm_system_time.c353
-rw-r--r--contrib/tsm_system_time/tsm_system_time.control6
7 files changed, 548 insertions, 0 deletions
diff --git a/contrib/tsm_system_time/.gitignore b/contrib/tsm_system_time/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/contrib/tsm_system_time/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/contrib/tsm_system_time/Makefile b/contrib/tsm_system_time/Makefile
new file mode 100644
index 0000000..6959995
--- /dev/null
+++ b/contrib/tsm_system_time/Makefile
@@ -0,0 +1,25 @@
+# contrib/tsm_system_time/Makefile
+
+MODULE_big = tsm_system_time
+OBJS = \
+ $(WIN32RES) \
+ tsm_system_time.o
+PGFILEDESC = "tsm_system_time - TABLESAMPLE method which accepts time in milliseconds as a limit"
+
+EXTENSION = tsm_system_time
+DATA = tsm_system_time--1.0.sql
+
+REGRESS = tsm_system_time
+
+SHLIB_LINK += $(filter -lm, $(LIBS))
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/tsm_system_time
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/tsm_system_time/expected/tsm_system_time.out b/contrib/tsm_system_time/expected/tsm_system_time.out
new file mode 100644
index 0000000..ac44f30
--- /dev/null
+++ b/contrib/tsm_system_time/expected/tsm_system_time.out
@@ -0,0 +1,100 @@
+CREATE EXTENSION tsm_system_time;
+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;
+-- It's a bit tricky to test SYSTEM_TIME in a platform-independent way.
+-- We can test the zero-time corner case ...
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (0);
+ count
+-------
+ 0
+(1 row)
+
+-- ... and we assume that this will finish before running out of time:
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (100000);
+ count
+-------
+ 31
+(1 row)
+
+-- bad parameters should get through planning, but not execution:
+EXPLAIN (COSTS OFF)
+SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
+ QUERY PLAN
+--------------------------------------------------
+ Sample Scan on test_tablesample
+ Sampling: system_time ('-1'::double precision)
+(2 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
+ERROR: sample collection time must not be negative
+-- fail, this method is not repeatable:
+SELECT * FROM test_tablesample TABLESAMPLE system_time (10) REPEATABLE (0);
+ERROR: tablesample method system_time does not support REPEATABLE
+LINE 1: SELECT * FROM test_tablesample TABLESAMPLE system_time (10) ...
+ ^
+-- since it's not repeatable, we expect a Materialize node in these plans:
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+ (VALUES (0),(100000)) v(time),
+ LATERAL (SELECT COUNT(*) FROM test_tablesample
+ TABLESAMPLE system_time (100000)) ss;
+ QUERY PLAN
+------------------------------------------------------------------------
+ Nested Loop
+ -> Aggregate
+ -> Materialize
+ -> Sample Scan on test_tablesample
+ Sampling: system_time ('100000'::double precision)
+ -> Values Scan on "*VALUES*"
+(6 rows)
+
+SELECT * FROM
+ (VALUES (0),(100000)) v(time),
+ LATERAL (SELECT COUNT(*) FROM test_tablesample
+ TABLESAMPLE system_time (100000)) ss;
+ time | count
+--------+-------
+ 0 | 31
+ 100000 | 31
+(2 rows)
+
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+ (VALUES (0),(100000)) v(time),
+ LATERAL (SELECT COUNT(*) FROM test_tablesample
+ TABLESAMPLE system_time (time)) ss;
+ QUERY PLAN
+----------------------------------------------------------------
+ Nested Loop
+ -> Values Scan on "*VALUES*"
+ -> Aggregate
+ -> Materialize
+ -> Sample Scan on test_tablesample
+ Sampling: system_time ("*VALUES*".column1)
+(6 rows)
+
+SELECT * FROM
+ (VALUES (0),(100000)) v(time),
+ LATERAL (SELECT COUNT(*) FROM test_tablesample
+ TABLESAMPLE system_time (time)) ss;
+ time | count
+--------+-------
+ 0 | 0
+ 100000 | 31
+(2 rows)
+
+CREATE VIEW vv AS
+ SELECT * FROM test_tablesample TABLESAMPLE system_time (20);
+EXPLAIN (COSTS OFF) SELECT * FROM vv;
+ QUERY PLAN
+--------------------------------------------------
+ Sample Scan on test_tablesample
+ Sampling: system_time ('20'::double precision)
+(2 rows)
+
+DROP EXTENSION tsm_system_time; -- fail, view depends on extension
+ERROR: cannot drop extension tsm_system_time because other objects depend on it
+DETAIL: view vv depends on function system_time(internal)
+HINT: Use DROP ... CASCADE to drop the dependent objects too.
diff --git a/contrib/tsm_system_time/sql/tsm_system_time.sql b/contrib/tsm_system_time/sql/tsm_system_time.sql
new file mode 100644
index 0000000..117de16
--- /dev/null
+++ b/contrib/tsm_system_time/sql/tsm_system_time.sql
@@ -0,0 +1,51 @@
+CREATE EXTENSION tsm_system_time;
+
+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;
+
+-- It's a bit tricky to test SYSTEM_TIME in a platform-independent way.
+-- We can test the zero-time corner case ...
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (0);
+-- ... and we assume that this will finish before running out of time:
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (100000);
+
+-- bad parameters should get through planning, but not execution:
+EXPLAIN (COSTS OFF)
+SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
+
+SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
+
+-- fail, this method is not repeatable:
+SELECT * FROM test_tablesample TABLESAMPLE system_time (10) REPEATABLE (0);
+
+-- since it's not repeatable, we expect a Materialize node in these plans:
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+ (VALUES (0),(100000)) v(time),
+ LATERAL (SELECT COUNT(*) FROM test_tablesample
+ TABLESAMPLE system_time (100000)) ss;
+
+SELECT * FROM
+ (VALUES (0),(100000)) v(time),
+ LATERAL (SELECT COUNT(*) FROM test_tablesample
+ TABLESAMPLE system_time (100000)) ss;
+
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+ (VALUES (0),(100000)) v(time),
+ LATERAL (SELECT COUNT(*) FROM test_tablesample
+ TABLESAMPLE system_time (time)) ss;
+
+SELECT * FROM
+ (VALUES (0),(100000)) v(time),
+ LATERAL (SELECT COUNT(*) FROM test_tablesample
+ TABLESAMPLE system_time (time)) ss;
+
+CREATE VIEW vv AS
+ SELECT * FROM test_tablesample TABLESAMPLE system_time (20);
+
+EXPLAIN (COSTS OFF) SELECT * FROM vv;
+
+DROP EXTENSION tsm_system_time; -- fail, view depends on extension
diff --git a/contrib/tsm_system_time/tsm_system_time--1.0.sql b/contrib/tsm_system_time/tsm_system_time--1.0.sql
new file mode 100644
index 0000000..c59d2e8
--- /dev/null
+++ b/contrib/tsm_system_time/tsm_system_time--1.0.sql
@@ -0,0 +1,9 @@
+/* contrib/tsm_system_time/tsm_system_time--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_system_time" to load this file. \quit
+
+CREATE FUNCTION system_time(internal)
+RETURNS tsm_handler
+AS 'MODULE_PATHNAME', 'tsm_system_time_handler'
+LANGUAGE C STRICT;
diff --git a/contrib/tsm_system_time/tsm_system_time.c b/contrib/tsm_system_time/tsm_system_time.c
new file mode 100644
index 0000000..0b50807
--- /dev/null
+++ b/contrib/tsm_system_time/tsm_system_time.c
@@ -0,0 +1,353 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_system_time.c
+ * support routines for SYSTEM_TIME tablesample method
+ *
+ * The desire here is to produce a random sample with as many rows as possible
+ * in no more than the specified amount of time. 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 time dependence, this method is necessarily unrepeatable.
+ * However, we do what we can to reduce surprising behavior by selecting
+ * the sampling pattern just once per query, much as in tsm_system_rows.
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ * contrib/tsm_system_time/tsm_system_time.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.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"
+#include "utils/spccache.h"
+
+PG_MODULE_MAGIC;
+
+PG_FUNCTION_INFO_V1(tsm_system_time_handler);
+
+
+/* Private state */
+typedef struct
+{
+ uint32 seed; /* random seed */
+ double millis; /* time limit for sampling */
+ instr_time start_time; /* scan start time */
+ 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 */
+} SystemTimeSamplerData;
+
+static void system_time_samplescangetsamplesize(PlannerInfo *root,
+ RelOptInfo *baserel,
+ List *paramexprs,
+ BlockNumber *pages,
+ double *tuples);
+static void system_time_initsamplescan(SampleScanState *node,
+ int eflags);
+static void system_time_beginsamplescan(SampleScanState *node,
+ Datum *params,
+ int nparams,
+ uint32 seed);
+static BlockNumber system_time_nextsampleblock(SampleScanState *node, BlockNumber nblocks);
+static OffsetNumber system_time_nextsampletuple(SampleScanState *node,
+ BlockNumber blockno,
+ OffsetNumber maxoffset);
+static uint32 random_relative_prime(uint32 n, pg_prng_state *randstate);
+
+
+/*
+ * Create a TsmRoutine descriptor for the SYSTEM_TIME method.
+ */
+Datum
+tsm_system_time_handler(PG_FUNCTION_ARGS)
+{
+ TsmRoutine *tsm = makeNode(TsmRoutine);
+
+ tsm->parameterTypes = list_make1_oid(FLOAT8OID);
+
+ /* See notes at head of file */
+ tsm->repeatable_across_queries = false;
+ tsm->repeatable_across_scans = false;
+
+ tsm->SampleScanGetSampleSize = system_time_samplescangetsamplesize;
+ tsm->InitSampleScan = system_time_initsamplescan;
+ tsm->BeginSampleScan = system_time_beginsamplescan;
+ tsm->NextSampleBlock = system_time_nextsampleblock;
+ tsm->NextSampleTuple = system_time_nextsampletuple;
+ tsm->EndSampleScan = NULL;
+
+ PG_RETURN_POINTER(tsm);
+}
+
+/*
+ * Sample size estimation.
+ */
+static void
+system_time_samplescangetsamplesize(PlannerInfo *root,
+ RelOptInfo *baserel,
+ List *paramexprs,
+ BlockNumber *pages,
+ double *tuples)
+{
+ Node *limitnode;
+ double millis;
+ double spc_random_page_cost;
+ double npages;
+ double ntuples;
+
+ /* Try to extract an estimate for the limit time spec */
+ limitnode = (Node *) linitial(paramexprs);
+ limitnode = estimate_expression_value(root, limitnode);
+
+ if (IsA(limitnode, Const) &&
+ !((Const *) limitnode)->constisnull)
+ {
+ millis = DatumGetFloat8(((Const *) limitnode)->constvalue);
+ if (millis < 0 || isnan(millis))
+ {
+ /* Default millis if the value is bogus */
+ millis = 1000;
+ }
+ }
+ else
+ {
+ /* Default millis if we didn't obtain a non-null Const */
+ millis = 1000;
+ }
+
+ /* Get the planner's idea of cost per page read */
+ get_tablespace_page_costs(baserel->reltablespace,
+ &spc_random_page_cost,
+ NULL);
+
+ /*
+ * Estimate the number of pages we can read by assuming that the cost
+ * figure is expressed in milliseconds. This is completely, unmistakably
+ * bogus, but we have to do something to produce an estimate and there's
+ * no better answer.
+ */
+ if (spc_random_page_cost > 0)
+ npages = millis / spc_random_page_cost;
+ else
+ npages = millis; /* even more bogus, but whatcha gonna do? */
+
+ /* Clamp to sane value */
+ npages = clamp_row_est(Min((double) baserel->pages, npages));
+
+ if (baserel->tuples > 0 && baserel->pages > 0)
+ {
+ /* Estimate number of tuples returned based on tuple density */
+ double density = baserel->tuples / (double) baserel->pages;
+
+ ntuples = npages * density;
+ }
+ else
+ {
+ /* For lack of data, assume one tuple per page */
+ ntuples = npages;
+ }
+
+ /* Clamp to the estimated relation size */
+ ntuples = clamp_row_est(Min(baserel->tuples, ntuples));
+
+ *pages = npages;
+ *tuples = ntuples;
+}
+
+/*
+ * Initialize during executor setup.
+ */
+static void
+system_time_initsamplescan(SampleScanState *node, int eflags)
+{
+ node->tsm_state = palloc0(sizeof(SystemTimeSamplerData));
+ /* Note the above leaves tsm_state->step equal to zero */
+}
+
+/*
+ * Examine parameters and prepare for a sample scan.
+ */
+static void
+system_time_beginsamplescan(SampleScanState *node,
+ Datum *params,
+ int nparams,
+ uint32 seed)
+{
+ SystemTimeSamplerData *sampler = (SystemTimeSamplerData *) node->tsm_state;
+ double millis = DatumGetFloat8(params[0]);
+
+ if (millis < 0 || isnan(millis))
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
+ errmsg("sample collection time must not be negative")));
+
+ sampler->seed = seed;
+ sampler->millis = millis;
+ sampler->lt = InvalidOffsetNumber;
+ sampler->doneblocks = 0;
+ /* start_time, lb will be initialized during first NextSampleBlock call */
+ /* we intentionally do not change nblocks/firstblock/step here */
+}
+
+/*
+ * Select next block to sample.
+ *
+ * Uses linear probing algorithm for picking next block.
+ */
+static BlockNumber
+system_time_nextsampleblock(SampleScanState *node, BlockNumber nblocks)
+{
+ SystemTimeSamplerData *sampler = (SystemTimeSamplerData *) node->tsm_state;
+ instr_time cur_time;
+
+ /* First call within scan? */
+ if (sampler->doneblocks == 0)
+ {
+ /* First scan within query? */
+ if (sampler->step == 0)
+ {
+ /* Initialize now that we have scan descriptor */
+ pg_prng_state 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 and start_time */
+ sampler->lb = sampler->firstblock;
+ INSTR_TIME_SET_CURRENT(sampler->start_time);
+ }
+
+ /* If we've read all blocks in relation, we're done */
+ if (++sampler->doneblocks > sampler->nblocks)
+ return InvalidBlockNumber;
+
+ /* If we've used up all the allotted time, we're done */
+ INSTR_TIME_SET_CURRENT(cur_time);
+ INSTR_TIME_SUBTRACT(cur_time, sampler->start_time);
+ if (INSTR_TIME_GET_MILLISEC(cur_time) >= sampler->millis)
+ 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_time_nextsampletuple(SampleScanState *node,
+ BlockNumber blockno,
+ OffsetNumber maxoffset)
+{
+ SystemTimeSamplerData *sampler = (SystemTimeSamplerData *) node->tsm_state;
+ OffsetNumber tupoffset = sampler->lt;
+
+ /* 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, pg_prng_state *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_time/tsm_system_time.control b/contrib/tsm_system_time/tsm_system_time.control
new file mode 100644
index 0000000..b1b9789
--- /dev/null
+++ b/contrib/tsm_system_time/tsm_system_time.control
@@ -0,0 +1,6 @@
+# tsm_system_time extension
+comment = 'TABLESAMPLE method which accepts time in milliseconds as a limit'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_system_time'
+relocatable = true
+trusted = true
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-06 20:34:25 +0000