Re: [BUGS] BUG #14750: Seq Scan instead of Index Scan works without limitation
От | buhhunyx@tut.by |
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Тема | Re: [BUGS] BUG #14750: Seq Scan instead of Index Scan works without limitation |
Дата | |
Msg-id | 714641500536440@web1m.yandex.ru обсуждение исходный текст |
Ответ на | Re: [BUGS] BUG #14750: Seq Scan instead of Index Scan works without limitation (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: [BUGS] BUG #14750: Seq Scan instead of Index Scan works without limitation
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Список | pgsql-bugs |
Seq Scan is fine except its ignore PRIMARY KEY and UNIQUE CONSTRAINT: in case result is found it should be immediatly returnedto avoid scan rest of data: # explain analyze select accountid from accounts where accountname = 'accountId50';Seq Scan on accounts (cost=0.00..2.50rows=1 width=12) (actual time=0.018..0.029 rows=1 loops=1) Filter: ((accountname)::text = 'accountId50'::text) Rows Removed by Filter: 119Planning time: 0.075 msExecution time: 0.048 ms In product no 'LIMIT 1' specified because first found result expected; in case of huge amout simple queries difference isvaluable: # explain analyze select accountid from accounts where accountname = 'accountId50' limit 1;Limit (cost=0.00..2.50 rows=1width=12) (actual time=0.016..0.016 rows=1 loops=1) -> Seq Scan on accounts (cost=0.00..2.50 rows=1 width=12) (actualtime=0.014..0.014 rows=1 loops=1) Filter: ((accountname)::text = 'accountId50'::text) Rows Removed byFilter: 50Planning time: 0.084 msExecution time: 0.035 ms -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
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