Re: Performance tuning on RedHat Enterprise Linux 3
От | Neil Conway |
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Тема | Re: Performance tuning on RedHat Enterprise Linux 3 |
Дата | |
Msg-id | 1102381333.1494.48.camel@localhost.localdomain обсуждение исходный текст |
Ответ на | Re: Performance tuning on RedHat Enterprise Linux 3 (Paul Tillotson <pntil@shentel.net>) |
Ответы |
Re: Performance tuning on RedHat Enterprise Linux 3
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Список | pgsql-general |
On Mon, 2004-12-06 at 19:37 -0500, Paul Tillotson wrote: > I seem to remember hearing that the memory limit on certain operations, > such as sorts, is not "enforced" (may the hackers correct me if I am > wrong); rather, the planner estimates how much a sort might take by > looking at the statistics for a table. > > If the statistics are wrong, however, the sort doesn't actually stay > within sort memory, and so the process consumes a very large amount of > memory, much more than the sort_mem configuration parameter should allow > it to. AFAIK this is not the case. sort_mem defines the in-memory buffer used _per_ sort operation. The problem you may be referring to is that multiple concurrent sort operations (possibly within a single backend) will each consume up to sort_mem, so the aggregate memory usage for sort operations may be significantly higher than sort_mem. -Neil
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