Re: fast defaults in heap_getattr vs heap_deform_tuple

From: Andres Freund <andres(at)anarazel(dot)de>
To: Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>
Cc: Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: fast defaults in heap_getattr vs heap_deform_tuple
Date: 2019-02-09 10:54:00
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On 2019-02-06 03:39:19 -0800, Andres Freund wrote:
> On 2019-02-06 10:25:56 +0000, Andrew Gierth wrote:
> > >>>>> "Andres" == Andres Freund <andres(at)anarazel(dot)de> writes:
> >
> > >> Cool. Here's the patch that I, after some commit message polishing,
> > >> plan to commit to 11 and master to fix the issue at hand.
> >
> > Andres> And pushed.
> >
> > Sorry I didn't spot this earlier, but... in the backpatch to v11, is the
> > expansion of the trigger tuple really unnecessary now? Since
> > heap_getattr is a macro, C-language triggers that aren't recompiled
> > won't see the default? So perhaps the expansion should be left in?
> There was some IRC conversation about this:
> RhodiumToad | andres: ping?
> RhodiumToad | n/m, sent mail
> andres | RhodiumToad: IDK, there's a lot of other heap_getattr calls, and most of them don't go
> | through GetTupleForTrigger(). So extensions need to be recompiled either way.
> andres | (I'll write that in a bit on list, in meeting now)
> RhodiumToad | right, but those other calls were already broken.
> RhodiumToad | whereas in a trigger, they'd have worked previously, but then break with your fix
> Myon | the list of packages in Debian where heap_getattr appears is postgresql-11, pglogical,
> | pgextwlist, citus, postgresql-plsh, wal2json, pg-cron, postgresql-rum
> RhodiumToad | it's not an encouraged interface
> I'm mildly disinclined to re-add the heap_expand_tuple, because it's not
> the only case, and the extensions named above don't seem like they'd
> specifically affected by the trigger path, but I'm not sure.

I put the expansion back for 11. Seems harmless enough. I'm planning to
send a reply to the minor release info to -packagers informing people
that extensions compiled after the minor release might not be compatible
with older servers (because they depend on getmissingattr() which
previously wasn't an exposed function)


Andres Freund

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