Subject: Re: Flaky vacuum truncate test in reloptions.sql
To: Michael Paquier <michael@paquier.xyz>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
References: <87tuotr2hh.fsf@ars-thinkpad> <YGLOWsO2bV7KLvh7@paquier.xyz>
From: Arseny Sher <a.sher@postgrespro.ru>
Message-ID: <78aad736-c653-92fd-45ac-4482729459c6@postgrespro.ru>
Date: Tue, 30 Mar 2021 16:22:18 +0300
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On 3/30/21 10:12 AM, Michael Paquier wrote:

 > Yep, this is the same problem as the one discussed for c2dc1a7, where
 > a concurrent checkpoint may cause a page to be skipped, breaking the
 > test.

Indeed, Alexander Lakhin pointed me to that commit after I wrote the 
message.

 > Why not just using DISABLE_PAGE_SKIPPING instead here?

I think this is not enough. DISABLE_PAGE_SKIPPING disables vm consulting 
(sets
aggressive=true in the routine); however, if the page is locked and
lazy_check_needs_freeze says there is nothing to freeze on it, we again 
don't
look at its contents closely.


-- cheers, arseny