Horton

Re: patch submission: truncate trailing nulls from heap rows to reduce the size of the null bitmap [Review]

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Josh Berkus <josh@agliodbs.com>
Cc: Jamie Martin <jameisonb@yahoo.com>, Amit Kapila <amit.kapila@huawei.com>, Andres Freund <andres@2ndquadrant.com>, Craig Ringer <craig@2ndquadrant.com>, Noah Misch <noah@leadboat.com>, Simon Riggs <simon@2ndquadrant.com>, Kevin Grittner <kgrittn@mail.com>, "<robertmhaas@gmail.com>" <robertmhaas@gmail.com>, "<pgsql-hackers@postgresql.org>" <pgsql-hackers@postgresql.org>
Date: 2013-06-27T18:11:59Z
Lists: pgsql-hackers 
Josh Berkus <josh@agliodbs.com> writes:
> So, is this patch currently depending on performance testing, or not?
> Like I said, it'll be a chunk of time to set up what I beleive is a
> realistic performance test, so I don't want to do it if the patch is
> likely to be bounced for other reasons.

AFAICS, the threshold question here is whether the patch helps usefully
for tables with typical numbers of columns (ie, not 800 ;-)), and
doesn't hurt materially in any common scenario.  If it does, I think
we'd take it.  I've not read the patch, so I don't know if there are
minor cosmetic or correctness issues, but at bottom this seems to be a
very straightforward performance tradeoff.

			regards, tom lane

Commits

  1. Don't assume that a tuple's header size is unchanged during toasting.