Message-ID: <c3a1bd51686c32f399b7f23e48aec4820e8bad15.camel@cybertec.at>
Subject: Re: Avoid Wraparound Failures
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Ron <ronljohnsonjr@gmail.com>, pgsql-admin@lists.postgresql.org
Date: Sat, 26 Mar 2022 05:50:32 +0100
In-Reply-To: <e94006fe-b953-720e-c6b8-a7f76145fa55@gmail.com>
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	 <965a52fe849ec6e5759d349b4063b5077353f24b.camel@cybertec.at>
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On Fri, 2022-03-25 at 23:45 -0500, Ron wrote:
> > If you want to prevent that autovacuum run from happening while your system is
> > busy (which normally also is no problem), you can trigger a manual VACUUM at
> > a time of lower database activity.  But make it a plain VACUUM, not a
> > VACUUM (FREEZE)
> 
> Why not VACUUM FREEZE?

Because then you freeze *all* visible rows, not only those that are older than
"vacuum_freeze_min_age".  That will cause more pages to get dirtied, so there will
be more writing I/O.  And unless all these rows won't get modified in the forseeable
future, that is a waste.  "vacuum_freeze_min_age" is there for a reason: the
expectation is that rows that have not been modified for 50 million transactions
have better odds at not getting modified soon.

Yours,
Laurenz Albe
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