Re: BUG #17916: Expression IN list translates to unqualified operator

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: rekgrpth(at)gmail(dot)com
Cc: pgsql-bugs(at)lists(dot)postgresql(dot)org
Subject: Re: BUG #17916: Expression IN list translates to unqualified operator
Date: 2023-05-03 13:40:44
Message-ID: 2956974.1683121244@sss.pgh.pa.us
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PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> create operator qwe.= (leftarg = char, rightarg = text, function =
> qwe.chartexteq, commutator = operator(qwe.=), hashes, merges);
> set search_path = qwe;
> explain (costs off, verbose on) select i from generate_series(1, 10) i where
> i::char in (2::text);

> I expected, that IN list translates to pg_catalog.=

Why would you expect that? It'd make it impossible to use IN
with user-defined data types. In this case, you made an operator
that is a closer match to the given datatypes (ie, "char = text")
than the native "text = text" operator, so it used that one.

I've not checked the code, but my recollection is that X IN (Y) just
resolves to the same equality operator you'd get by writing X = Y.
There's been some discussion about allowing a schema qualifier to
be included in the syntax, but nothing's been done about that.

regards, tom lane

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