From: | Andres Freund <andres(at)anarazel(dot)de> |
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To: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Changed SRF in targetlist handling |
Date: | 2016-08-22 19:01:01 |
Message-ID: | 20160822190101.5r3thmffjl62tn3f@alap3.anarazel.de |
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Thread: | |
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
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