Re: Query performance issue

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От Greg Sabino Mullane
Тема Re: Query performance issue
Дата
Msg-id CAKAnmmKMzXaUeVg-WLVReCOD-=+8GUq8=Uc7a0jfU6DgzPZ_Yg@mail.gmail.com
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Ответ на Re: Query performance issue  (yudhi s <learnerdatabase99@gmail.com>)
Ответы Re: Query performance issue
Re: Query performance issue
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To be frank, there is so much wrong with this query that it is hard to know where to start. But a few top items:

* Make sure all of the tables involved have been analyzed. You might want to bump default_statistics_target up and see if that helps.

* As mentioned already, increase work_mem, as you have things spilling to disk (e.g. external merge Disk: 36280kB)

* Don't use the "FROM table1, table2, table3" syntax but use "FROM table1 JOIN table2 ON (...) JOIN table3 ON (...)

* Try not to use subselects. Things like WHERE x IN (SELECT ...) are expensive and hard to optimize.

* You have useless GROUP BY clauses in there. Remove to simplify the query

* There is no LIMIT. Does the client really need all 135,214 rows?

Cheers,
Greg

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