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From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
To: pgsql-performance@postgresql.org
Subject: Re: [HACKERS] Slow count(*) again...
Date: Fri, 04 Feb 2011 14:28:08 +1300
Message-ID: <4D4B5628.8030100@catalyst.net.nz> (raw)
In-Reply-To: <4D4B4D30.2060007@wizmail.org>
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On 04/02/11 13:49, Jeremy Harris wrote:
> On 2011-02-03 21:51, Mark Kirkwood wrote:
>> The cases I've seen in production typically involve "outgrowing" 
>> optimizer parameter settings: (e.g work_mem, effective_cache_size) as 
>> the application dataset gets bigger over time.
>
> An argument in favour of the DBMS maintaining a running estimate of 
> such things.

That is an interesting idea - I'm not quite sure how it could apply to 
server config settings (e.g work_mem) for which it would be dangerous to 
allow the server to increase on the fly, but it sure would be handy to 
have some sort of query execution "memory" so that alerts like:

"STATEMENT: SELECT blah  : PARAMETERS blah: using temp file(s), last 
execution used memory"

could be generated (this could be quite complex I guess, requiring some 
sort of long lived statement plan cache).

Cheers

Mark

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