From: Tom Lane <tgl@sss.pgh.pa.us>
To: =?UTF-8?Q?Fr=C3=A9d=C3=A9ric_Yhuel?= <frederic.yhuel@dalibo.com>
cc: "pgsql-performance@lists.postgresql.org"
 <pgsql-performance@lists.postgresql.org>,
        Jehan-Guillaume de Rorthais <jgdr@dalibo.com>,
        Christophe Courtois <christophe.courtois@dalibo.com>,
        Laurenz Albe <laurenz.albe@cybertec.at>
Subject: Re: Indexes on expressions with multiple columns and operators
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Comments: In-reply-to =?UTF-8?Q?Fr=C3=A9d=C3=A9ric_Yhuel?=
 <frederic.yhuel@dalibo.com>
	message dated "Wed, 17 Sep 2025 16:57:26 +0200"
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Date: Thu, 18 Sep 2025 11:32:29 -0400
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=?UTF-8?Q?Fr=C3=A9d=C3=A9ric_Yhuel?= <frederic.yhuel@dalibo.com> writes:
> On 9/17/25 16:41, Tom Lane wrote:
>> =?UTF-8?Q?Fr=C3=A9d=C3=A9ric_Yhuel?= <frederic.yhuel@dalibo.com> writes:
>>> 2) the number of estimated rows is completely off in the second EXPLAIN,
>>> whereas the planner could easily use the statistics of foo_f_idx.

>> Hmm, not sure about that.  Again, boolean-valued indexes aren't
>> something we've worked on too hard, but I don't see why that
>> would affect this case.

> OK, thanks anyway, I think the ju-jitsu mentioned above will do, even 
> though the application code will have to be patched.

Sigh ... so the answer is this used to work (since commit 39df0f150)
and then I carelessly broke it in commit a391ff3c3.  If you try this
test case in versions 9.5..11 you get a spot-on rowcount estimate.
Serves me right for not having a test case I guess, but I'm astonished
that nobody complained sooner.

			regards, tom lane