Re: BUG #19449: Massive performance degradation for complex query on Postgres 16+ (few seconds -> multiple hours)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Tomas Vondra <tomas(at)vondra(dot)me>
Cc: Adrian Mönnich <adrian(dot)moennich(at)cern(dot)ch>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-bugs(at)lists(dot)postgresql(dot)org, Tomas Vondra <tv(at)fuzzy(dot)cz>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Subject: Re: BUG #19449: Massive performance degradation for complex query on Postgres 16+ (few seconds -> multiple hours)
Date: 2026-04-02 22:43:36
Message-ID: 3675338.1775169816@sss.pgh.pa.us
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Tomas Vondra <tomas(at)vondra(dot)me> writes:
> An interesting question is "What changed in PG16?" causing the query to
> fail, when it worked OK on earlier versions.

"git bisect" could be informative here. I agree with trying to
minimize the query first, though --- else you may waste time
going down blind alleys, as a result of planner changes changing
the join order without affecting the critical executor behavior.

regards, tom lane

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