Horton

Re: Changed SRF in targetlist handling

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Craig Ringer <craig@2ndquadrant.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2016-08-22T19:01:01Z
Lists: pgsql-hackers 
Hi,

On 2016-05-23 09:26:03 +0800, Craig Ringer wrote:
> SRFs-in-tlist are a lot faster for lockstep iteration etc. They're also
> much simpler to write, though if the result result rowcount differs
> unexpectedly between the functions you get exciting and unexpected
> behaviour.
> 
> WITH ORDINALITY provides what I think is the last of the functionality
> needed to replace SRFs-in-from, but at a syntatactic complexity and
> performance cost. The following example demonstrates that, though it
> doesn't do anything that needs LATERAL etc. I'm aware the following aren't
> semantically identical if the rowcounts differ.

I think here you're just missing ROWS FROM (generate_series(..), generate_series(...))

Andres

Commits

  1. Remove obsoleted code relating to targetlist SRF evaluation.

  2. Doc: improve documentation of new SRF-in-tlist behavior.

  3. Move targetlist SRF handling from expression evaluation to new executor node.

  4. Don't split up SRFs when choosing to postpone SELECT output expressions.