103 lines
3.8 KiB
PL/PgSQL
103 lines
3.8 KiB
PL/PgSQL
CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10);
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-- use fillfactor so we don't have to load too much data to get multiple pages
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INSERT INTO test_tablesample
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SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i);
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SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (0);
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (0);
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
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SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (0);
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SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (0);
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-- 100% should give repeatable count results (ie, all rows) in any case
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SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
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SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (1+2);
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SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (0.4);
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CREATE VIEW test_tablesample_v1 AS
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
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CREATE VIEW test_tablesample_v2 AS
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
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\d+ test_tablesample_v1
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\d+ test_tablesample_v2
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-- check a sampled query doesn't affect cursor in progress
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BEGIN;
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DECLARE tablesample_cur CURSOR FOR
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
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FETCH FIRST FROM tablesample_cur;
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FETCH NEXT FROM tablesample_cur;
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FETCH NEXT FROM tablesample_cur;
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (0);
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FETCH NEXT FROM tablesample_cur;
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FETCH NEXT FROM tablesample_cur;
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FETCH NEXT FROM tablesample_cur;
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FETCH FIRST FROM tablesample_cur;
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FETCH NEXT FROM tablesample_cur;
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FETCH NEXT FROM tablesample_cur;
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FETCH NEXT FROM tablesample_cur;
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FETCH NEXT FROM tablesample_cur;
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FETCH NEXT FROM tablesample_cur;
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CLOSE tablesample_cur;
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END;
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EXPLAIN (COSTS OFF)
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (2);
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EXPLAIN (COSTS OFF)
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SELECT * FROM test_tablesample_v1;
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-- check inheritance behavior
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explain (costs off)
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select count(*) from person tablesample bernoulli (100);
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select count(*) from person tablesample bernoulli (100);
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select count(*) from person;
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-- check that collations get assigned within the tablesample arguments
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SELECT count(*) FROM test_tablesample TABLESAMPLE bernoulli (('1'::text < '0'::text)::int);
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-- check behavior during rescans, as well as correct handling of min/max pct
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select * from
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(values (0),(100)) v(pct),
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lateral (select count(*) from tenk1 tablesample bernoulli (pct)) ss;
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select * from
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(values (0),(100)) v(pct),
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lateral (select count(*) from tenk1 tablesample system (pct)) ss;
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explain (costs off)
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select pct, count(unique1) from
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(values (0),(100)) v(pct),
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lateral (select * from tenk1 tablesample bernoulli (pct)) ss
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group by pct;
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select pct, count(unique1) from
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(values (0),(100)) v(pct),
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lateral (select * from tenk1 tablesample bernoulli (pct)) ss
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group by pct;
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select pct, count(unique1) from
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(values (0),(100)) v(pct),
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lateral (select * from tenk1 tablesample system (pct)) ss
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group by pct;
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-- errors
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SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (NULL);
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
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SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (-1);
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SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (200);
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (-1);
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SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (200);
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SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
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INSERT INTO test_tablesample_v1 VALUES(1);
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WITH query_select AS (SELECT * FROM test_tablesample)
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SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
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SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
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