From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alexander Okulovich <aokulovich@stiltsoft.com>
cc: pgsql-performance@postgresql.org
Subject: Re: Postgres 15 SELECT query doesn't use index under RLS
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Comments: In-reply-to Alexander Okulovich <aokulovich@stiltsoft.com>
	message dated "Wed, 18 Oct 2023 16:07:38 +0200"
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Date: Wed, 18 Oct 2023 16:35:50 -0400
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Alexander Okulovich <aokulovich@stiltsoft.com> writes:
> We used the product with the default settings. The requests are simple. 
> We didn't change the hardware (actually, we use even more performant 
> hardware because of that issue) and DDL. I've checked the request on old 
> and new databases. Requests that rely on this index execute more than 10 
> times longer. Planner indeed used Index Scan before, but now it doesn't.

> So, from my perspective, the only reason we experience that is database 
> logic change.

[ shrug... ]  Maybe, but it's still not clear if it's a bug, or an
intentional change, or just a cost estimate that was on the hairy
edge before and your luck ran out.

If you could provide a self-contained test case that performs 10x worse
under v15 than v12, we'd surely take a look at it.  But with the
information you've given so far, little is possible beyond speculation.

			regards, tom lane