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Re: Indexes on expressions with multiple columns and operators

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Frédéric 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>
Date: 2025-09-18T15:32:29Z
Lists: pgsql-performance 
=?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

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Re-allow using statistics for bool-valued functions in WHERE.

  2. Build out the planner support function infrastructure.

  3. Allow planner to use expression-index stats for function calls in WHERE.