Re: Numeric performances
От | PFC |
---|---|
Тема | Re: Numeric performances |
Дата | |
Msg-id | op.tteomsebcigqcu@apollo13 обсуждение исходный текст |
Ответ на | Re: Numeric performances (Tom Lane <tgl@sss.pgh.pa.us>) |
Список | pgsql-general |
> If you try it with max() you'd likely get less-surprising answers. So it was in fact the type conversions that got timed. Damn. I got outsmarted XDD Rewind : CREATE TEMPORARY TABLE test AS SELECT a::FLOAT AS f, (a::NUMERIC)*100000000000000 AS n, a::INTEGER AS i, a::BIGINT AS b FROM generate_series( 1,100000 ) AS a; Max and Sort will use comparisons : SELECT max(i) FROM test; SELECT max(b) FROM test; SELECT max(f) FROM test; SELECT max(n) FROM test; Temps : 42,132 ms Temps : 59,499 ms Temps : 58,808 ms Temps : 54,197 ms SELECT * FROM test ORDER BY i LIMIT 1; SELECT * FROM test ORDER BY b LIMIT 1; SELECT * FROM test ORDER BY f LIMIT 1; SELECT * FROM test ORDER BY n LIMIT 1; Temps : 58,723 ms Temps : 60,520 ms Temps : 53,188 ms Temps : 61,779 ms SELECT count(*) FROM test a JOIN test b ON (a.i=b.i); Temps : 275,411 ms SELECT count(*) FROM test a JOIN test b ON (a.b=b.b); Temps : 286,132 ms SELECT count(*) FROM test a JOIN test b ON (a.f=b.f); Temps : 295,956 ms SELECT count(*) FROM test a JOIN test b ON (a.n=b.n); Temps : 321,292 ms SELECT count(*) FROM test a JOIN test b ON (a.i=b.b); Temps : 281,162 ms SELECT count(*) FROM test a JOIN test b ON (a.n=b.i::NUMERIC*100000000000000); Temps : 454,706 ms Now, addition : SELECT count(i+1) FROM test; Temps : 46,973 ms SELECT count(b+1) FROM test; Temps : 60,027 ms SELECT count(f+1) FROM test; Temps : 56,829 ms SELECT count(n+1) FROM test; Temps : 103,316 ms Multiplication : SELECT count(i*1) FROM test; Temps : 46,950 ms SELECT count(b*1) FROM test; Temps : 58,670 ms SELECT count(f*1) FROM test; Temps : 57,058 ms SELECT count(n*1) FROM test; Temps : 108,379 ms SELECT count(i) FROM test; Temps : 38,351 ms SELECT count(i/1234) FROM test; Temps : 48,961 ms SELECT count(b/1234) FROM test; Temps : 62,496 ms SELECT count(n/1234) FROM test; Temps : 186,674 ms Conclusion : numeric seems a bit slower (division being slowest obviously) but nothing that can't be swamped by a few disk seeks...
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