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Re: Does RelCache/SysCache shrink except when relations are deleted?

From: Merlin Moncure <mmoncure(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, MauMau <maumau307(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Does RelCache/SysCache shrink except when relations are deleted?
Date: 2011-09-29 15:43:38
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Thu, Sep 29, 2011 at 10:22 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> I can't really explain why people seem to keep wanting to create
> hundreds of thousands or even millions of tables, but it's not like
> MauMau's customer is the first one to try to do this, and I'm sure
> they won't be the last.  I don't want to de-optimize the more common
> (and sensible) cases too much, but "slow" still trumps "fails
> outright".

Yeah -- maybe baby steps in the right direction would be track cache
memory usage and add instrumentation so the user could get a readout
on usage -- this would also help us diagnose memory issues in the
field.  Also, thinking about it more, a DISCARD based cache flush
(DISCARD CACHES TO xyz) wrapping a monolithic LRU sweep could help
users deal with these cases without having to figure out how to make
an implementation that pleases everyone.


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