45 lines
1.4 KiB
SQL
45 lines
1.4 KiB
SQL
--
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-- SELECT_DISTINCT_ON
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--
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SELECT DISTINCT ON (string4) string4, two, ten
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FROM onek
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ORDER BY string4 using <, two using >, ten using <;
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-- this will fail due to conflict of ordering requirements
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SELECT DISTINCT ON (string4, ten) string4, two, ten
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FROM onek
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ORDER BY string4 using <, two using <, ten using <;
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SELECT DISTINCT ON (string4, ten) string4, ten, two
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FROM onek
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ORDER BY string4 using <, ten using >, two using <;
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-- bug #5049: early 8.4.x chokes on volatile DISTINCT ON clauses
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select distinct on (1) floor(random()) as r, f1 from int4_tbl order by 1,2;
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--
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-- Test the planner's ability to use a LIMIT 1 instead of a Unique node when
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-- all of the distinct_pathkeys have been marked as redundant
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--
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-- Ensure we also get a LIMIT plan with DISTINCT ON
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EXPLAIN (COSTS OFF)
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SELECT DISTINCT ON (four) four,two
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FROM tenk1 WHERE four = 0 ORDER BY 1;
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-- and check the result of the above query is correct
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SELECT DISTINCT ON (four) four,two
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FROM tenk1 WHERE four = 0 ORDER BY 1;
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-- Ensure a Sort -> Limit is used when the ORDER BY contains additional cols
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EXPLAIN (COSTS OFF)
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SELECT DISTINCT ON (four) four,two
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FROM tenk1 WHERE four = 0 ORDER BY 1,2;
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-- Same again but use a column that is indexed so that we get an index scan
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-- then a limit
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EXPLAIN (COSTS OFF)
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SELECT DISTINCT ON (four) four,hundred
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FROM tenk1 WHERE four = 0 ORDER BY 1,2;
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