From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Dilger <mark.dilger@enterprisedb.com>
cc: Michael Paquier <michael@paquier.xyz>,
        Andrew Dunstan <andrew@dunslane.net>, Noah Misch <noah@leadboat.com>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Fixing WAL instability in various TAP tests
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Comments: In-reply-to Mark Dilger <mark.dilger@enterprisedb.com>
	message dated "Tue, 28 Sep 2021 11:07:54 -0700"
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Date: Tue, 28 Sep 2021 14:20:18 -0400
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Mark Dilger <mark.dilger@enterprisedb.com> writes:
> Looking closer at the TAP test, it's not ORDERing the result set from th=
e SELECTs on either node, but it is comparing the sets for stringwise equa=
lity, which is certainly order dependent.

Well, it's forcing a bitmap scan, so what we're getting is the native
ordering of a bitmapscan result.  That should match, given that what
we're doing is physical replication.  I think adding ORDER BY would
be more likely to obscure real issues than hide test instability.

			regards, tom lane