explain analyze reports that my queries are fast but they run very slowly

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От Nikolas Everett
Тема explain analyze reports that my queries are fast but they run very slowly
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Msg-id CAPmjWd2XgV9d3zy3zc8L9PJRdoVM720g2zSQWsDKZsJkOqKMjw@mail.gmail.com
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Ответы Re: explain analyze reports that my queries are fast but they run very slowly  (François Beausoleil <francois@teksol.info>)
Re: explain analyze reports that my queries are fast but they run very slowly  (Tom Lane <tgl@sss.pgh.pa.us>)
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We just upgraded from 8.3 to 9.1 and we're seeing some performance problems.  When we EXPLAIN ANALYZE our queries the explain result claim that the queries are reasonably fast but the wall clock time is way way longer.  Does anyone know why this might happen?

Like so:
db=>\timing
db=>EXPLAIN ANALYZE SELECT max(id) FROM foo WHERE blah_id = 1209123;

The plan is sensible.  The estimates are sensible.  The actual DB time reads like it is very sensible.  But the wall clock time is like 11 seconds and the \timing report confirms it.

Any ideas?

Thanks!

Nik

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