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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org, Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Subject: Re: WIP: Faster Expression Processing v4
Date: Wed, 15 Mar 2017 18:16:57 -0400
Message-ID: <9137.1489616217@sss.pgh.pa.us> (raw)
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Andres Freund <andres@anarazel.de> writes:
> On 2017-03-15 17:33:46 -0400, Tom Lane wrote:
>> We could make the planner mark each table scan node with the highest
>> column number that the plan will access, and use that to drive a
>> slot_getsomeattrs call in advance of any access to tuple contents.

> probably isn't sufficient - we build non-virtual tuples in a good number
> of places (sorts, tuplestore using stuff like nodeMaterial, nodeHash.c
> output, ...).  I suspect it'd have measurable negative consequences if
> we removed the deforming logic for all expressions/projections above
> such nodes.  I guess we could just do such a logic for every Plan node?

[ scratches head... ]  What deforming logic do you think I'm proposing
removing?

			regards, tom lane


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