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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Dilger <mark.dilger@enterprisedb.com>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: Andrew Dunstan <andrew@dunslane.net>
Cc: Noah Misch <noah@leadboat.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Fixing WAL instability in various TAP tests
Date: Tue, 28 Sep 2021 14:20:18 -0400
Message-ID: <2855067.1632853218@sss.pgh.pa.us> (raw)
In-Reply-To: <0AE9B97A-EE55-41DD-A913-CDBCAA8E2214@enterprisedb.com>
References: <32A1FDD1-9C7B-43B1-B3EE-49198DD3F887@enterprisedb.com>
	<20210925052151.GA4082552@rfd.leadboat.com>
	<2E9D28A3-1B54-446B-AC12-3BF86A2B522A@enterprisedb.com>
	<2502590.1632579467@sss.pgh.pa.us>
	<2B4C64CF-EE3F-474B-9685-6A927E5E49AE@enterprisedb.com>
	<20210925160039.GA4134968@rfd.leadboat.com>
	<193AC968-C348-4D81-88BC-384560F87500@enterprisedb.com>
	<C1D227C2-C271-4310-8C85-C5368C298622@enterprisedb.com>
	<2769443.1632773967@sss.pgh.pa.us>
	<YVJXEf119KrJDFdq@paquier.xyz>
	<2801531.1632795612@sss.pgh.pa.us>
	<2852500.1632850031@sss.pgh.pa.us>
	<0AE9B97A-EE55-41DD-A913-CDBCAA8E2214@enterprisedb.com>

Mark Dilger <mark.dilger@enterprisedb.com> writes:
> Looking closer at the TAP test, it's not ORDERing the result set from the SELECTs on either node, but it is comparing the sets for stringwise equality, 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





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