pg.ddx.io pgsql-hackers@postgresql.org mailing list archive help / color / mirror / Atom feed From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: Jesper Pedersen <jesper.pedersen@redhat.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: POC: converting Lists into arrays
Date: Sun, 21 Jul 2019 10:45:32 -0400
Message-ID: <1733.1563720332@sss.pgh.pa.us> (raw )
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David Rowley <david.rowley@2ndquadrant.com> writes:
> On Wed, 17 Jul 2019 at 11:06, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> (Actually, I doubt that any of these changes will really move the
>> performance needle in the real world. It's more a case of wanting
>> the code to present good examples not bad ones.)
> In spirit with the above, I'd quite like to fix a small bad example
> that I ended up with in nodeAppend.c and nodeMergeappend.c for
> run-time partition pruning.
I didn't test the patch, but just by eyeball it looks sane,
and I concur it should win if the bitmap is sparse.
One small question is whether it loses if most of the subplans
are present in the bitmap. I imagine that would be close enough
to break-even, but it might be worth trying to test to be sure.
(I'd think about breaking out just the loops in question and
testing them stand-alone, or else putting in an outer loop to
repeat them, since as you say the surrounding work probably
dominates.)
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, david.rowley@2ndquadrant.com, jesper.pedersen@redhat.com, andres@anarazel.de, robertmhaas@gmail.com, pgsql-hackers@lists.postgresql.org
Subject: Re: POC: converting Lists into arrays
In-Reply-To: <1733.1563720332@sss.pgh.pa.us>
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