From: Heikki Linnakangas <hlinnaka@iki.fi>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: select_common_typmod
Date: Mon, 26 Oct 2020 11:05:11 +0200
Message-ID: <3152222d-4792-d75b-46a8-de22ebb0de31@iki.fi> (raw)
In-Reply-To: <97df3af9-8b5e-fb7f-a029-3eb7e80d7af9@2ndquadrant.com>
References: <97df3af9-8b5e-fb7f-a029-3eb7e80d7af9@2ndquadrant.com>
On 20/10/2020 11:58, Peter Eisentraut wrote:
> While working on another patch, I figured adding a
> select_common_typmod() to go along with select_common_type() and
> select_common_collation() would be handy. Typmods were previously
> combined using hand-coded logic in several places, and not at all in
> other places. The logic in select_common_typmod() isn't very exciting,
> but it makes the code more compact and readable in a few locations, and
> in the future we can perhaps do more complicated things if desired.
Makes sense.
> There might have been a tiny bug in transformValuesClause() because
> while consolidating the typmods it does not take into account whether
> the types are actually the same (as more correctly done in
> transformSetOperationTree() and buildMergedJoinVar()).
Hmm, it seems so, but I could not come up with a test case to reach that
codepath. I think you'd need to create two types in the same
typcategory, but with different and incompatible typmod formats.
The patch also adds typmod resolution for hypothetical ordered-set
aggregate arguments. I couldn't come up with a test case that would
tickle that codepath either, but it seems like a sensible change. You
might want to mention it in the commit message though.
- Heikki
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To: pgsql-hackers@postgresql.org
Cc: hlinnaka@iki.fi, peter.eisentraut@2ndquadrant.com
Subject: Re: select_common_typmod
In-Reply-To: <3152222d-4792-d75b-46a8-de22ebb0de31@iki.fi>
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