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38d81760c4
There is already a version of this in contrib/tablefunc, but it seems sufficiently widely useful to justify having it in core. Paul Ramsey Discussion: https://postgr.es/m/CACowWR0DqHAvOKUCNxTrASFkWsDLqKMd6WiXvVvaWg4pV1BMnQ@mail.gmail.com
68 lines
1.8 KiB
SQL
68 lines
1.8 KiB
SQL
--
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-- RANDOM
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-- Test the random function
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--
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-- count the number of tuples originally, should be 1000
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SELECT count(*) FROM onek;
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-- pick three random rows, they shouldn't match
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(SELECT unique1 AS random
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FROM onek ORDER BY random() LIMIT 1)
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INTERSECT
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(SELECT unique1 AS random
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FROM onek ORDER BY random() LIMIT 1)
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INTERSECT
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(SELECT unique1 AS random
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FROM onek ORDER BY random() LIMIT 1);
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-- count roughly 1/10 of the tuples
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CREATE TABLE RANDOM_TBL AS
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SELECT count(*) AS random
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FROM onek WHERE random() < 1.0/10;
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-- select again, the count should be different
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INSERT INTO RANDOM_TBL (random)
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SELECT count(*)
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FROM onek WHERE random() < 1.0/10;
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-- select again, the count should be different
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INSERT INTO RANDOM_TBL (random)
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SELECT count(*)
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FROM onek WHERE random() < 1.0/10;
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-- select again, the count should be different
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INSERT INTO RANDOM_TBL (random)
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SELECT count(*)
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FROM onek WHERE random() < 1.0/10;
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-- now test that they are different counts
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SELECT random, count(random) FROM RANDOM_TBL
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GROUP BY random HAVING count(random) > 3;
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SELECT AVG(random) FROM RANDOM_TBL
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HAVING AVG(random) NOT BETWEEN 80 AND 120;
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-- now test random_normal()
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TRUNCATE random_tbl;
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INSERT INTO random_tbl (random)
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SELECT count(*)
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FROM onek WHERE random_normal(0, 1) < 0;
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INSERT INTO random_tbl (random)
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SELECT count(*)
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FROM onek WHERE random_normal(0) < 0;
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INSERT INTO random_tbl (random)
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SELECT count(*)
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FROM onek WHERE random_normal() < 0;
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INSERT INTO random_tbl (random)
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SELECT count(*)
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FROM onek WHERE random_normal(stddev => 1, mean => 0) < 0;
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-- expect similar, but not identical values
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SELECT random, count(random) FROM random_tbl
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GROUP BY random HAVING count(random) > 3;
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-- approximately check expected distribution
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SELECT AVG(random) FROM random_tbl
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HAVING AVG(random) NOT BETWEEN 400 AND 600;
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