From: Tom Lane <tgl@sss.pgh.pa.us>
To: joan@sanchezsabe.com
cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18851: Queries with xxx NOT IN (SELECT xxx FROM table) fail
 to run (or run very slowly) on v17 (v14 ok)
In-reply-to: <18851-5a0a9801290135d7@postgresql.org>
References: <18851-5a0a9801290135d7@postgresql.org>
Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
	message dated "Fri, 14 Mar 2025 16:16:06 -0000"
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Date: Fri, 14 Mar 2025 12:56:54 -0400
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PG Bug reporting form <noreply@postgresql.org> writes:
> I have experienced a misbehaviour (IMHO) in PostgreSQL 17 that didn't occur
> in PostgreSQL 14.

What have you got work_mem set to in the two installations?

For me, both versions switch to the cheap hashed plan if work_mem
is large enough that the inner table is estimated to fit in it
(somewhere around 10MB-20MB for this specific example).  If anything
the newer code seems to have a smaller threshold.

			regards, tom lane