From: Tom Lane <tgl@sss.pgh.pa.us>
To: Noah Misch <noah@leadboat.com>
Cc: Francesco Degrassi <francesco.degrassi@optionfactory.net>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: Leader backend hang on IPC/ParallelFinish when LWLock held at parallel query start
Date: Wed, 18 Sep 2024 01:45:31 -0400
Message-ID: <1748003.1726638331@sss.pgh.pa.us> (raw)
In-Reply-To: <20240918053026.79.nmisch@google.com>
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<20240918030159.2a.nmisch@google.com>
<1737570.1726633422@sss.pgh.pa.us>
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<1744648.1726636728@sss.pgh.pa.us>
<20240918053026.79.nmisch@google.com>
Noah Misch <noah@leadboat.com> writes:
> What if we just ignored the plancache when uninterruptible? The new planner
> check would then suffice.
Only if you believe that parallel-query is the only problem,
which is something I seriously doubt. I fear that the
committed patch is just a band-aid over one symptom of the
general problem that we can't permit arbitrary operations
to be invoked from a btree comparison function. It's late
here so I'm not sufficiently awake to think of examples,
but I'm sure there are some.
However ... clearly a maliciously-coded btree support function can
do arbitrarily bad stuff. We restrict creation of opclasses to
superusers for exactly that reason. If our ambitions are only
to prevent support functions from *accidentally* causing problems,
is disabling parallel query enough? I'm still pretty uncomfortable
about it, but it's less obviously insufficient than in the general
case.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, noah@leadboat.com, francesco.degrassi@optionfactory.net, pgsql-bugs@lists.postgresql.org
Subject: Re: Leader backend hang on IPC/ParallelFinish when LWLock held at parallel query start
In-Reply-To: <1748003.1726638331@sss.pgh.pa.us>
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