From: Tom Lane <tgl@sss.pgh.pa.us>
To: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
cc: Tomas Vondra <tomas@vondra.me>, pgsql-performance@lists.postgresql.org,
        "P.Groidis" <itdev@gatewaynet.com>
Subject: Re: tds_fdw : Severe performance degradation from postgresql 10.23 to
 16.4
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Comments: In-reply-to Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
	message dated "Tue, 12 Nov 2024 20:24:09 +0200"
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Date: Tue, 12 Nov 2024 14:37:36 -0500
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Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> writes:
> Our sysadm created the system debian Debian GNU/Linux 12 (bookworm)with 
> postgres as user 1000. Now at some point we realized that whenever we 
> run a pgsql cluster with another user (I found that after spending two 
> good days testing), the above query runs in about 1 second. With user 
> postgres 1000 in 30 seconds. As you saw the perf output are completely 
> different.

Don't recall details offhand, but in some situations where the calling
SQL user doesn't have permissions to read particular columns, the
planner will not consult statistics for those columns.  That can lead
to a different, less optimal plan being used.  Maybe something like
that is happening here?

			regards, tom lane