Re: Hints WAS: Index Tuning Features
От | Zeugswetter Andreas ADI SD |
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Тема | Re: Hints WAS: Index Tuning Features |
Дата | |
Msg-id | E1539E0ED7043848906A8FF995BDA579016A09CC@m0143.s-mxs.net обсуждение исходный текст |
Ответ на | Re: Hints WAS: Index Tuning Features (Josh Berkus <josh@agliodbs.com>) |
Список | pgsql-hackers |
> And, to give you a starting point: the discussion has morphed into: > "What manual ways can we come up with for the DBA to > influence the planner and fix planner "bugs" which won't have > the fragility of query-based hints ala Oracle?" I see a few downsides though: 1. it lacks a way to try out different plans in one sessionwithout actually influencing other sessions. Maybe the way to do this is:begin work;add statistics hintsexplain analyze your selectrollback work; this is not enough to try a whole program with a new manual correction though. 2. To try out sensible plans would only work if there where ways that allow all nodetypes (on specific tables/where clauses) to be made more/less expensive individually. 3. the manual entry may negatively influence other queries that previously were fastthus a typical tuning measure for one bad query plan imposes high risk 4. sometimes I know as a developer that certain queries only run in case of abnormal skew in data (e.g. I expect to get a lot of rows even if usually i would get few) Andreas
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