| From: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, PG Hackers <pgsql-hackers(at)postgresql(dot)org>, Greg Stark <stark(at)mit(dot)edu>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, David Fetter <david(at)fetter(dot)org> |
| Subject: | Re: Review: UNNEST (and other functions) WITH ORDINALITY |
| Date: | 2013-07-29 07:56:45 |
| Message-ID: | 51F6203D.4080507@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 07/25/2013 02:01 AM, Andres Freund wrote:
> And much of that can trivially/centrally be rewritten to LATERAL, not
> to speak of the cross-version compatibility problem.
An interesting example of that can be found here:
http://stackoverflow.com/q/12414750/398670
where someone's looking for a way to "zip" two arrays pairwise into an
array of arrays.
As far as I can tell LATERAL won't help with this; you'd need unnest
WITH ORDINALITY then a join on the ordinal, or you'd need full support
for SQL UNNEST with multiple array arguments.
Unless LATERAL provides a way to do lock-step iteration through a pair
(or more) of functions I don't think we can get rid of SRFs-in-FROM just
yet.
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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