Re: speed of querry?
От | Tom Lane |
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Тема | Re: speed of querry? |
Дата | |
Msg-id | 8324.1113604689@sss.pgh.pa.us обсуждение исходный текст |
Ответ на | Re: speed of querry? ("Joel Fradkin" <jfradkin@wazagua.com>) |
Список | pgsql-performance |
"Joel Fradkin" <jfradkin@wazagua.com> writes: > Turning off merg joins seems to of done it but what do I need to do so I am > not telling the system explicitly not to use them, I must be missing some > setting? > " -> Hash Left Join (cost=185.57..226218.77 rows=177236 width=75) (actual > time=21.147..2221.098 rows=177041 loops=1)" > " Hash Cond: (("outer".jobtitleid = "inner".id) AND > (("outer".clientnum)::text = ("inner".clientnum)::text))" It's overestimating the cost of this join for some reason ... and I think I see why. It's not accounting for the combined effect of the two hash clauses, only for the "better" one. What are the statistics for tbljobtitle.id and tbljobtitle.clientnum --- how many distinct values of each, and are the distributions skewed to a few popular values? regards, tom lane
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