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help / color / mirror / Atom feedFrom: MichaelDBA <[email protected]>
To: Tom Lane <[email protected]>
Cc: Wells Oliver <[email protected]>
Cc: pgsql-admin <[email protected]>
Subject: Re: CTEs and temp_buffers?
Date: Tue, 26 Apr 2022 14:55:54 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CAOC+FBXvpUcTwH5ec0KK7A+MOmRkXDC3xy069ykzEC1asDKi3A@mail.gmail.com>
<[email protected]>
Hi Tom,
Of course, you're right! I got sidetracked thinking about temp_buffers
with respect to temporary tables and not CTEs where work_mem stuff would
apply. But back to the temp_buffers thing. Can you acknowledge that my
thinking is right about that? That temporary table buffers if exceeding
temp_buffers gets logged to the *<datadir>/base/pgsql_tmp* area and is
not logged in the logs at all? My testing seems to confirm that.
Tom Lane wrote on 4/26/2022 2:03 PM:
> Wells Oliver <[email protected]> writes:
>> Out of curiosity, does the value of temp_buffers apply to how CTEs are
>> generated under the hood?
> No. Intermediate results within a query (whether CTE or not) might
> get spilled to disk in a "temporary file", but that's a distinct
> mechanism from temp tables, which is what temp_buffers applies to.
>
> Bruce's nearby answer explains how you can control/monitor temp
> files, but he didn't actually answer your question ;-)
>
> regards, tom lane
>
>
Regards,
Michael Vitale, Sr. PostgreSQL DBA
[email protected] <mailto:[email protected]>
703-600-9343
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