mirror of
https://github.com/postgres/postgres.git
synced 2026-02-03 20:40:14 -05:00
bed9ef5a16
As suggested by Tom Lane, avoid printing specific estimated cost values, because they vary across architectures; instead, verify plan shapes (in this case, HashAggregate vs. GroupAggregate), as we do in other planner tests. We can now remove expected/stats_ext_1.out. Author: Tomas Vondra
165 lines
4.5 KiB
SQL
165 lines
4.5 KiB
SQL
-- Generic extended statistics support
|
|
|
|
-- We will be checking execution plans without/with statistics, so
|
|
-- let's make sure we get simple non-parallel plans. Also set the
|
|
-- work_mem low so that we can use small amounts of data.
|
|
SET max_parallel_workers = 0;
|
|
SET max_parallel_workers_per_gather = 0;
|
|
SET work_mem = '128kB';
|
|
|
|
-- Ensure stats are dropped sanely
|
|
CREATE TABLE ab1 (a INTEGER, b INTEGER, c INTEGER);
|
|
CREATE STATISTICS ab1_a_b_stats ON (a, b) FROM ab1;
|
|
DROP STATISTICS ab1_a_b_stats;
|
|
|
|
CREATE SCHEMA regress_schema_2;
|
|
CREATE STATISTICS regress_schema_2.ab1_a_b_stats ON (a, b) FROM ab1;
|
|
|
|
-- Let's also verify the pg_get_statisticsextdef output looks sane.
|
|
SELECT pg_get_statisticsextdef(oid) FROM pg_statistic_ext WHERE staname = 'ab1_a_b_stats';
|
|
|
|
DROP STATISTICS regress_schema_2.ab1_a_b_stats;
|
|
|
|
-- Ensure statistics are dropped when columns are
|
|
CREATE STATISTICS ab1_b_c_stats ON (b, c) FROM ab1;
|
|
CREATE STATISTICS ab1_a_b_c_stats ON (a, b, c) FROM ab1;
|
|
CREATE STATISTICS ab1_a_b_stats ON (a, b) FROM ab1;
|
|
ALTER TABLE ab1 DROP COLUMN a;
|
|
\d ab1
|
|
DROP TABLE ab1;
|
|
|
|
-- Ensure things work sanely with SET STATISTICS 0
|
|
CREATE TABLE ab1 (a INTEGER, b INTEGER);
|
|
ALTER TABLE ab1 ALTER a SET STATISTICS 0;
|
|
INSERT INTO ab1 SELECT a, a%23 FROM generate_series(1, 1000) a;
|
|
CREATE STATISTICS ab1_a_b_stats ON (a, b) FROM ab1;
|
|
ANALYZE ab1;
|
|
ALTER TABLE ab1 ALTER a SET STATISTICS -1;
|
|
ANALYZE ab1;
|
|
DROP TABLE ab1;
|
|
|
|
|
|
-- n-distinct tests
|
|
CREATE TABLE ndistinct (
|
|
filler1 TEXT,
|
|
filler2 NUMERIC,
|
|
a INT,
|
|
b INT,
|
|
filler3 DATE,
|
|
c INT,
|
|
d INT
|
|
);
|
|
|
|
-- over-estimates when using only per-column statistics
|
|
INSERT INTO ndistinct (a, b, c, filler1)
|
|
SELECT i/100, i/100, i/100, cash_words((i/100)::money)
|
|
FROM generate_series(1,30000) s(i);
|
|
|
|
ANALYZE ndistinct;
|
|
|
|
-- Group Aggregate, due to over-estimate of the number of groups
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY b, c;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d;
|
|
|
|
-- unknown column
|
|
CREATE STATISTICS s10 ON (unknown_column) FROM ndistinct;
|
|
|
|
-- single column
|
|
CREATE STATISTICS s10 ON (a) FROM ndistinct;
|
|
|
|
-- single column, duplicated
|
|
CREATE STATISTICS s10 ON (a,a) FROM ndistinct;
|
|
|
|
-- two columns, one duplicated
|
|
CREATE STATISTICS s10 ON (a, a, b) FROM ndistinct;
|
|
|
|
-- correct command
|
|
CREATE STATISTICS s10 ON (a, b, c) FROM ndistinct;
|
|
|
|
ANALYZE ndistinct;
|
|
|
|
SELECT staenabled, standistinct
|
|
FROM pg_statistic_ext WHERE starelid = 'ndistinct'::regclass;
|
|
|
|
-- Hash Aggregate, thanks to estimates improved by the statistic
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY b, c;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c;
|
|
|
|
-- last two plans keep using Group Aggregate, because 'd' is not covered
|
|
-- by the statistic and while it's NULL-only we assume 200 values for it
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d;
|
|
|
|
TRUNCATE TABLE ndistinct;
|
|
|
|
-- under-estimates when using only per-column statistics
|
|
INSERT INTO ndistinct (a, b, c, filler1)
|
|
SELECT mod(i,50), mod(i,51), mod(i,32),
|
|
cash_words(mod(i,33)::int::money)
|
|
FROM generate_series(1,10000) s(i);
|
|
|
|
ANALYZE ndistinct;
|
|
|
|
SELECT staenabled, standistinct
|
|
FROM pg_statistic_ext WHERE starelid = 'ndistinct'::regclass;
|
|
|
|
-- plans using Group Aggregate, thanks to using correct esimates
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, d;
|
|
|
|
DROP STATISTICS s10;
|
|
|
|
SELECT staenabled, standistinct
|
|
FROM pg_statistic_ext WHERE starelid = 'ndistinct'::regclass;
|
|
|
|
-- dropping the statistics switches the plans to Hash Aggregate,
|
|
-- due to under-estimates
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, b, c, d;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY b, c, d;
|
|
|
|
EXPLAIN (COSTS off)
|
|
SELECT COUNT(*) FROM ndistinct GROUP BY a, d;
|
|
|
|
DROP TABLE ndistinct;
|