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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
cc: Michael Paquier <michael@paquier.xyz>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>,
        Alexander Lakhin <exclusion@gmail.com>
Subject: Re: A failure in prepared_xacts test
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Comments: In-reply-to Richard Guo <guofenglinux@gmail.com>
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Date: Mon, 29 Apr 2024 21:48:13 -0400
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Richard Guo <guofenglinux@gmail.com> writes:
> +1.  I'm kind of worried that the expansion of parallelization could
> lead to more instances of instability.  Alexander mentioned one such
> case at [1].  I haven't looked into it though.
> [1] https://www.postgresql.org/message-id/cbf0156f-5aa1-91db-5802-82435d=
da03e6%40gmail.com

The mechanism there is pretty obvious: a plancache flush happened
at just the wrong (right?) time and caused the output to change,
as indeed the comment acknowledges:

 -- currently, this fails due to cached plan for "r.f1 + 1" expression
 -- (but if debug_discard_caches is on, it will succeed)

I wonder if we shouldn't just remove that test case as being
too unstable -- especially since it's not proving much anyway.

			regards, tom lane