Re: Implement targetlist SRFs using ROWS FROM() (was Changed SRF in targetlist handling)

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

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org
Date: 2016-09-12T17:48:05Z
Lists: pgsql-hackers
Andres Freund <andres@anarazel.de> writes:
> On 2016-09-12 13:26:20 -0400, Tom Lane wrote:
>> Andres Freund <andres@anarazel.de> writes:
> On 2016-09-12 12:10:01 -0400, Tom Lane wrote:
>>>> I can't say that I like the proposed syntax much.

>>> Me neither. But I haven't really found a better approach.  It seems
>>> kinda consistent to have ROWS FROM (... AS ()) change the picked out
>>> columns to 0, and just return the whole thing.

>> I just remembered that we allow zero-column composite types, which
>> makes this proposal formally ambiguous.  So we really need a different
>> syntax.  I'm not especially in love with the cast-to-record idea, but
>> it does dodge that problem.

> I kind of like ROWS FROM (... AS VALUE), that seems to confer the
> meaning quite well. As VALUE isn't a reserved keyword, that'd afaik only
> really work inside ROWS FROM() where AS is required.

Hm, wouldn't ... AS RECORD convey the meaning better?

(Although once you look at it that way, it's just a cast spelled in
an idiosyncratic fashion.)

			regards, tom lane


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.