On 2016-09-12 11:29:37 -0400, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: > > 0002-Shore-up-some-weird-corner-cases-for-targetlist-SRFs.patch > > Forbid UPDATE ... SET foo = SRF() and ORDER BY / GROUP BY containing > > SRFs that would change the number of returned rows. Without the > > latter e.g. SELECT 1 ORDER BY generate_series(1,10); returns 10 rows. > > I'm on board with disallowing SRFs in UPDATE, because it produces > underdetermined and unspecified results; but the other restriction > seems 100% arbitrary. There is no semantic difference between > SELECT a, b FROM ... ORDER BY srf(); > and > SELECT a, b, srf() FROM ... ORDER BY 3; > except that in the first case the ordering column doesn't get returned to > the client. I do not see why that's so awful that we should make it fail > after twenty years of allowing it.
I do think it's awful that an ORDER BY / GROUP BY changes the number of rows processed. This should never have been allowed. You just need a little typo somewhere that makes the targetlist entry not match the ORDER/GROUP BY anymore and your results will differ in weird ways - rather hard to debug in the GROUP BY case. > And I certainly don't see why there > would be an implementation reason why we couldn't support it anymore > if we can still do the second one. There's nothing requiring this here, indeed. Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
