From: Tom Lane <tgl@sss.pgh.pa.us>
To: Titus von Boxberg <titus@elbe-informatik.de>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: strange and slow joining of nested views
Date: Sat, 04 Feb 2017 00:16:21 -0500
Message-ID: <20264.1486185381@sss.pgh.pa.us> (raw)
In-Reply-To: <e94d7a48bb564ed69feb0affec2d71a4@SOLOWJOW.ELBE.local>
References: <e94d7a48bb564ed69feb0affec2d71a4@SOLOWJOW.ELBE.local>
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Titus von Boxberg <titus@elbe-informatik.de> writes:
> I got the following problem for which I could not find a solution by searching the archives:
> I have Tables Ta, Tb, Tc with primary keys as bigserials.
> Ta references Tb references Tc.
> Not all but most rows in Ta reference exactly one row in Tb.
Hm, your problem query has 11 table scans (not to mention a couple of
subplans) so you're oversimplifying here. Anyway, I think that increasing
join_collapse_limit and/or from_collapse_limit to at least 11 might help.
As-is, you're more or less at the mercy of whether your textual query
structure corresponds to a good join order.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, titus@elbe-informatik.de
Subject: Re: strange and slow joining of nested views
In-Reply-To: <20264.1486185381@sss.pgh.pa.us>
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