101 lines
3.4 KiB
Plaintext
101 lines
3.4 KiB
Plaintext
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CREATE EXTENSION tsm_system_time;
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CREATE TABLE test_tablesample (id int, name text);
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INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000)
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FROM generate_series(0, 30) s(i);
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ANALYZE test_tablesample;
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-- It's a bit tricky to test SYSTEM_TIME in a platform-independent way.
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-- We can test the zero-time corner case ...
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SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (0);
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count
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-------
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0
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(1 row)
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-- ... and we assume that this will finish before running out of time:
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SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (100000);
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count
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-------
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31
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(1 row)
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-- bad parameters should get through planning, but not execution:
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EXPLAIN (COSTS OFF)
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SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
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QUERY PLAN
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--------------------------------------------------
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Sample Scan on test_tablesample
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Sampling: system_time ('-1'::double precision)
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(2 rows)
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SELECT id FROM test_tablesample TABLESAMPLE system_time (-1);
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ERROR: sample collection time must not be negative
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-- fail, this method is not repeatable:
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SELECT * FROM test_tablesample TABLESAMPLE system_time (10) REPEATABLE (0);
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ERROR: tablesample method system_time does not support REPEATABLE
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LINE 1: SELECT * FROM test_tablesample TABLESAMPLE system_time (10) ...
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^
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-- since it's not repeatable, we expect a Materialize node in these plans:
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EXPLAIN (COSTS OFF)
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SELECT * FROM
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(VALUES (0),(100000)) v(time),
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LATERAL (SELECT COUNT(*) FROM test_tablesample
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TABLESAMPLE system_time (100000)) ss;
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QUERY PLAN
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------------------------------------------------------------------------
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Nested Loop
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-> Aggregate
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-> Materialize
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-> Sample Scan on test_tablesample
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Sampling: system_time ('100000'::double precision)
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-> Values Scan on "*VALUES*"
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(6 rows)
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SELECT * FROM
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(VALUES (0),(100000)) v(time),
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LATERAL (SELECT COUNT(*) FROM test_tablesample
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TABLESAMPLE system_time (100000)) ss;
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time | count
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--------+-------
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0 | 31
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100000 | 31
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(2 rows)
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EXPLAIN (COSTS OFF)
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SELECT * FROM
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(VALUES (0),(100000)) v(time),
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LATERAL (SELECT COUNT(*) FROM test_tablesample
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TABLESAMPLE system_time (time)) ss;
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QUERY PLAN
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----------------------------------------------------------------
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Nested Loop
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-> Values Scan on "*VALUES*"
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-> Aggregate
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-> Materialize
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-> Sample Scan on test_tablesample
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Sampling: system_time ("*VALUES*".column1)
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(6 rows)
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SELECT * FROM
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(VALUES (0),(100000)) v(time),
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LATERAL (SELECT COUNT(*) FROM test_tablesample
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TABLESAMPLE system_time (time)) ss;
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time | count
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--------+-------
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0 | 0
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100000 | 31
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(2 rows)
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CREATE VIEW vv AS
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SELECT * FROM test_tablesample TABLESAMPLE system_time (20);
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EXPLAIN (COSTS OFF) SELECT * FROM vv;
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QUERY PLAN
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--------------------------------------------------
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Sample Scan on test_tablesample
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Sampling: system_time ('20'::double precision)
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(2 rows)
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DROP EXTENSION tsm_system_time; -- fail, view depends on extension
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ERROR: cannot drop extension tsm_system_time because other objects depend on it
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DETAIL: view vv depends on function system_time(internal)
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HINT: Use DROP ... CASCADE to drop the dependent objects too.
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