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Re: Properly initialize negative/empty cache entries in relfilenodemap - Mailing list pgsql-hackers

From didier
Subject Re: Properly initialize negative/empty cache entries in relfilenodemap
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Msg-id CAJRYxuKVt+acXpxFNZ0NkgWJTZ36GmcLSbvVWuft24vZuvvCsA@mail.gmail.com
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In response to Re: Properly initialize negative/empty cache entries in relfilenodemap  ("MauMau" <maumau307@gmail.com>)
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Hi,

On Thu, Aug 29, 2013 at 2:35 PM, MauMau <maumau307@gmail.com> wrote:

Great!  Could anybody find the root cause for the following memory leak problem, and if possible, fix this?

http://www.postgresql.org/message-id/214653D8DF574BFEAA6ED53E545E99E4@maumau

Heiki helped to solve this and found that pg_statistic entries are left in CacheMemoryContext, but we have no idea where and how they are created and left.  This seems difficult to me.

VALGRIND  won't help you for this one
You hit 2 issues
- user can create negative cache entries in pg_statistic with SELECT but they are unbound (at first there was a LRU aging but it was removed in 2006)

- if there's no row in pg_statistic for a relation/column then RemoveStatistics, called by DROP ..., doesn't invalidate the cache (which should remove these negative entries).

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