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Re: anti-join chosen even when slower than old plan

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: anti-join chosen even when slower than old plan
Date: 2010-11-09 23:24:48
Message-ID: 4CD983E002000025000374D7@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-performance
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
 
> However, you'd have to be spending a lot of time chasing through
> long HOT chains before that would happen enough to make this a
> hotspot...
 
That makes it all the more mysterious, then.  These tables are
insert-only except for a weekly delete of one week of the oldest
data.  The parent table, with the date, is deleted first, then this
table deletes "where not exists" a corresponding parent.  I can't
see how we'd ever have a HOT chain in these tables.
 
Is there anything in particular you'd like me to check?
 
-Kevin

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Subject: Re: Huge overestimation in rows expected results in bad plan
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