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Add contrib/pgbench extension exposing benchmark functions in SCHEMA pgbench
Add a new contrib extension `pgbench` that exposes the extracted distribution, permutation, and hashing functions as SQL-callable routines in schema `pgbench`: - pgbench.random(min, max) - pgbench.random_gaussian(min, max, parameter) - pgbench.random_exponential(min, max, parameter) - pgbench.random_zipfian(min, max, parameter) - pgbench.random_poisson(center) - pgbench.hash_murmur2(val, seed) - pgbench.hash_fnv1a(val, seed) - pgbench.hash(val, seed) - pgbench.permute(val, size, seed) - pgbench.setseed(seed) Includes regression test suite and build definitions for both Make and Meson.
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‎contrib/Makefile‎

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@@ -44,6 +44,7 @@ SUBDIRS = \
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pgstattuple \
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pg_visibility \
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pg_walinspect \
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pgbench \
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postgres_fdw \
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seg \
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spi \

‎contrib/meson.build‎

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@@ -58,6 +58,7 @@ subdir('pg_surgery')
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subdir('pg_trgm')
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subdir('pg_visibility')
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subdir('pg_walinspect')
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subdir('pgbench')
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subdir('postgres_fdw')
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subdir('seg')
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subdir('sepgsql')

‎contrib/pgbench/Makefile‎

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# contrib/pgbench/Makefile
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MODULE_big = pgbench
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OBJS = \
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$(WIN32RES) \
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pgbench.o \
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pgbench_funcs.o
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EXTENSION = pgbench
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DATA = pgbench--1.0.sql
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PGFILEDESC = "pgbench - random distributions and benchmarking utilities"
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REGRESS = pgbench
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EXTRA_CLEAN = pgbench_funcs.c
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ifdef USE_PGXS
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PG_CONFIG = pg_config
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PGXS := $(shell $(PG_CONFIG) --pgxs)
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include $(PGXS)
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else
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subdir = contrib/pgbench
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top_builddir = ../..
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include $(top_builddir)/src/Makefile.global
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include $(top_srcdir)/contrib/contrib-global.mk
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endif
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# pgbench_funcs.c is shared from src/common
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pgbench_funcs.c: % : $(top_srcdir)/src/common/%
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rm -f $@ && $(LN_S) $< .

‎contrib/pgbench/expected/pgbench.out‎

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CREATE EXTENSION pgbench;
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-- Check schema and functions
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\dx+ pgbench
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Objects in extension "pgbench"
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Object description
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---------------------------------------------------------------------
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function pgbench.hash(bigint,bigint)
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function pgbench.hash_fnv1a(bigint,bigint)
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function pgbench.hash_murmur2(bigint,bigint)
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function pgbench.permute(bigint,bigint,bigint)
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function pgbench.random(bigint,bigint)
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function pgbench.random_exponential(bigint,bigint,double precision)
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function pgbench.random_gaussian(bigint,bigint,double precision)
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function pgbench.random_poisson(double precision)
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function pgbench.random_zipfian(bigint,bigint,double precision)
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function pgbench.setseed(bigint)
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function pgbench.setseed(double precision)
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(11 rows)
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-- Test Hashing functions
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SELECT pgbench.hash_murmur2(12345, 0);
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hash_murmur2
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----------------------
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-8599128181304237022
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(1 row)
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SELECT pgbench.hash_murmur2(12345, 42);
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hash_murmur2
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---------------------
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-591810079667318857
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(1 row)
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SELECT pgbench.hash_fnv1a(12345, 0);
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hash_fnv1a
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----------------------
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-1792800413050876852
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(1 row)
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SELECT pgbench.hash_fnv1a(12345, 42);
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hash_fnv1a
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----------------------
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-5267424053501251834
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(1 row)
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-- pgbench.hash is alias for hash_murmur2
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SELECT pgbench.hash(12345, 0) = pgbench.hash_murmur2(12345, 0);
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?column?
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----------
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t
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(1 row)
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SELECT pgbench.hash(12345, 42) = pgbench.hash_murmur2(12345, 42);
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?column?
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----------
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t
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(1 row)
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-- Test Permutation function (bijective mapping over 0..9)
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SELECT array_agg(pgbench.permute(i, 10, 42) ORDER BY i) FROM generate_series(0, 9) i;
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array_agg
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-----------------------
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{1,7,0,4,3,8,6,5,9,2}
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(1 row)
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SELECT count(DISTINCT pgbench.permute(i, 10, 42)) = 10 FROM generate_series(0, 9) i;
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?column?
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----------
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t
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(1 row)
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SELECT count(DISTINCT pgbench.permute(i, 100, 12345)) = 100 FROM generate_series(0, 99) i;
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?column?
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----------
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t
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(1 row)
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-- Test setseed and reproducibility
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SELECT pgbench.setseed(0.5);
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setseed
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---------
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(1 row)
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SELECT pgbench.random(1, 100) AS r_unif,
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pgbench.random_gaussian(1, 100, 2.5) AS r_gauss,
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pgbench.random_exponential(1, 100, 3.0) AS r_exp,
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pgbench.random_zipfian(1, 100, 1.5) AS r_zipf,
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pgbench.random_poisson(50.0) AS r_poiss;
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r_unif | r_gauss | r_exp | r_zipf | r_poiss
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--------+---------+-------+--------+---------
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17 | 60 | 61 | 50 | 36
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(1 row)
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-- Reset seed and verify exact same values
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SELECT pgbench.setseed(0.5);
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setseed
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---------
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(1 row)
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SELECT pgbench.random(1, 100) AS r_unif,
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pgbench.random_gaussian(1, 100, 2.5) AS r_gauss,
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pgbench.random_exponential(1, 100, 3.0) AS r_exp,
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pgbench.random_zipfian(1, 100, 1.5) AS r_zipf,
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pgbench.random_poisson(50.0) AS r_poiss;
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r_unif | r_gauss | r_exp | r_zipf | r_poiss
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--------+---------+-------+--------+---------
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17 | 60 | 61 | 50 | 36
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(1 row)
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-- Test bigint setseed
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SELECT pgbench.setseed(123456789::bigint);
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setseed
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---------
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(1 row)
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SELECT pgbench.random(1, 100);
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random
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--------
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(1 row)
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SELECT pgbench.setseed(123456789::bigint);
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setseed
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---------
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(1 row)
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SELECT pgbench.random(1, 100);
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random
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--------
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(1 row)
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-- Error cases: parameter boundaries
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SELECT pgbench.random(10, 5);
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ERROR: empty range given to random: lower bound 10 is greater than upper bound 5
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SELECT pgbench.random_gaussian(1, 10, 1.5);
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ERROR: gaussian parameter must be at least 2.000000 (not 1.500000)
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SELECT pgbench.random_exponential(1, 10, 0.0);
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ERROR: exponential parameter must be greater than zero (not 0.000000)
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SELECT pgbench.random_zipfian(1, 10, 1.0);
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ERROR: zipfian parameter must be in range [1.001, 1000] (not 1.000000)
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SELECT pgbench.random_zipfian(1, 10, 1001.0);
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ERROR: zipfian parameter must be in range [1.001, 1000] (not 1001.000000)
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SELECT pgbench.random_poisson(0.0);
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ERROR: poisson center parameter must be greater than zero (not 0.000000)
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SELECT pgbench.permute(5, 0, 42);
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ERROR: permute size parameter must be greater than zero
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SELECT pgbench.setseed(1.5);
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ERROR: setseed parameter 1.5 is out of allowed range [-1,1]
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DROP EXTENSION pgbench;

‎contrib/pgbench/meson.build‎

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# Copyright (c) 2026, PostgreSQL Global Development Group
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pgbench_ext_sources = files(
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'pgbench.c',
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'../../src/common/pgbench_funcs.c',
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)
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if host_system == 'windows'
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pgbench_ext_sources += rc_lib_gen.process(win32ver_rc, extra_args: [
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'--NAME', 'pgbench',
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'--FILEDESC', 'pgbench - random distributions and benchmarking utilities',])
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endif
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pgbench_ext = shared_module('pgbench',
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pgbench_ext_sources,
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c_pch: pch_postgres_h,
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kwargs: contrib_mod_args,
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)
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contrib_targets += pgbench_ext
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install_data(
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'pgbench.control',
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'pgbench--1.0.sql',
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kwargs: contrib_data_args,
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)
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tests += {
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'name': 'pgbench_ext',
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'sd': meson.current_source_dir(),
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'bd': meson.current_build_dir(),
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'regress': {
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'sql': [
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'pgbench',
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],
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},
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}

‎contrib/pgbench/pgbench--1.0.sql‎

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/* contrib/pgbench/pgbench--1.0.sql */
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-- complain if script is sourced in psql, rather than via CREATE EXTENSION
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\echo Use "CREATE EXTENSION pgbench" to load this file. \quit
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-- PRNG Seeding
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CREATE FUNCTION setseed(seed double precision)
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RETURNS void
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AS 'MODULE_PATHNAME', 'pgbench_setseed_double'
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LANGUAGE C STRICT VOLATILE PARALLEL RESTRICTED;
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CREATE FUNCTION setseed(seed bigint)
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RETURNS void
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AS 'MODULE_PATHNAME', 'pgbench_setseed_int64'
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LANGUAGE C STRICT VOLATILE PARALLEL RESTRICTED;
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-- Uniform Random
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CREATE FUNCTION random(min bigint, max bigint)
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RETURNS bigint
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AS 'MODULE_PATHNAME', 'pgbench_random_int64'
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LANGUAGE C STRICT VOLATILE PARALLEL RESTRICTED;
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-- Gaussian (Normal) Random
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CREATE FUNCTION random_gaussian(min bigint, max bigint, parameter double precision)
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RETURNS bigint
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AS 'MODULE_PATHNAME', 'pgbench_random_gaussian_int64'
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LANGUAGE C STRICT VOLATILE PARALLEL RESTRICTED;
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-- Exponential Random
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CREATE FUNCTION random_exponential(min bigint, max bigint, parameter double precision)
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RETURNS bigint
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AS 'MODULE_PATHNAME', 'pgbench_random_exponential_int64'
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LANGUAGE C STRICT VOLATILE PARALLEL RESTRICTED;
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-- Zipfian Random
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CREATE FUNCTION random_zipfian(min bigint, max bigint, parameter double precision)
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RETURNS bigint
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AS 'MODULE_PATHNAME', 'pgbench_random_zipfian_int64'
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LANGUAGE C STRICT VOLATILE PARALLEL RESTRICTED;
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-- Poisson Random
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CREATE FUNCTION random_poisson(center double precision)
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RETURNS bigint
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AS 'MODULE_PATHNAME', 'pgbench_random_poisson_int64'
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LANGUAGE C STRICT VOLATILE PARALLEL RESTRICTED;
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-- MurmurHash2 (64-bit)
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CREATE FUNCTION hash_murmur2(val bigint, seed bigint DEFAULT 0)
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RETURNS bigint
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AS 'MODULE_PATHNAME', 'pgbench_hash_murmur2_int64'
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LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;
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-- FNV-1a Hash (64-bit)
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CREATE FUNCTION hash_fnv1a(val bigint, seed bigint DEFAULT 0)
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RETURNS bigint
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AS 'MODULE_PATHNAME', 'pgbench_hash_fnv1a_int64'
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LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;
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-- Alias for hash_murmur2
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CREATE FUNCTION hash(val bigint, seed bigint DEFAULT 0)
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RETURNS bigint
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AS 'MODULE_PATHNAME', 'pgbench_hash_murmur2_int64'
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LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;
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-- Pseudorandom Permutation
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CREATE FUNCTION permute(val bigint, size bigint, seed bigint DEFAULT 0)
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RETURNS bigint
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AS 'MODULE_PATHNAME', 'pgbench_permute_int64'
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LANGUAGE C STRICT IMMUTABLE PARALLEL SAFE;

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