From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org, Atri Sharma <atri(dot)jiit(at)gmail(dot)com> |
Subject: | Re: Re: Patch to add functionality to specify ORDER BY in CREATE FUNCTION for SRFs |
Date: | 2015-01-05 17:54:41 |
Message-ID: | 1330.1420480481@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> Atri Sharma wrote
>> If order of result rows is not the same as required, an error is raised:
>>
>> SELECT * FROM incorrect_order_nulls() ORDER BY e NULLS LAST;
>> ERROR: Order not same as specified
> First reaction for the error was unfavorable but (see below) it likely is
> the best option and does adequately cover the reason for failure -
> programmer error.
TBH, my first reaction to this entire patch is unfavorable: it's a
solution in search of a problem. It adds substantial complication not
only for users but for PG developers in order to solve a rather narrow
performance issue.
What would make sense to me is to teach the planner about inlining
SQL functions that include ORDER BY clauses, so that the performance
issue of a double sort could be avoided entirely transparently to
the user.
regards, tom lane
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