From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Regina Obe <lr(at)pcorp(dot)us>, "'PostgreSQL-development'" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: PostgreSQL 10 changes in exclusion constraints - did something change? CASE WHEN behavior oddity |
Date: | 2017-06-03 02:53:00 |
Message-ID: | 7181.1496458380@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2017-05-28 14:03:26 -0400, Tom Lane wrote:
>> I think it would be possible to teach eval_const_expressions that
>> it must not discard CASE/COALESCE subexpressions that contain SRFs,
>> which would preserve the rule that expression simplification doesn't
>> change the query semantics.
> That sounds like a good idea. Do you want to write up a patch, or
> should I? I can, but I'd want to finish the walsender panic and other
> signal handling stuff first (mostly waiting for review for now).
I think you've got enough on your plate. I can take care of whatever
we decide to do here. What I was looking for was opinions on which
way to address it.
>> Another possibility is to say that we've broken this situation
>> irretrievably and we should start throwing errors for SRFs in
>> places where they'd be conditionally evaluated. That's not real
>> nice perhaps, but it's better than the way things are right now.
> I'd be ok with that too, but I don't really see a strong need so far.
The argument for this way is basically that it's better to break
apps visibly than silently. The behavior for SRF-inside-CASE is
not going to be the same as before even if we implement the fix
I suggest above, and it's arguable that this new behavior is not
at all intuitive.
I'm not really sure which way to jump, which is why I was hoping
for some discussion here.
regards, tom lane
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