From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Cc: Bossart, Nathan <bossartn@amazon.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: New vacuum option to do only freezing
Date: Tue, 16 Apr 2019 16:00:15 -0400
Message-ID: <7519.1555444815@sss.pgh.pa.us> (raw)
In-Reply-To: <31782.1555433074@sss.pgh.pa.us>
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<31782.1555433074@sss.pgh.pa.us>
I wrote:
> I'm thinking that we really need to upgrade vacuum's reporting totals
> so that it accounts in some more-honest way for pre-existing dead
> line pointers. The patch as it stands has made the reporting even more
> confusing, rather than less so.
Here's a couple of ideas about that:
1. Ignore heap_page_prune's activity altogether, on the grounds that
it's just random chance that any cleanup done there was done during
VACUUM and not some preceding DML operation. Make tups_vacuumed
be the count of dead line pointers removed. The advantage of this
way is that tups_vacuumed would become independent of previous
non-VACUUM pruning activity, as well as preceding index-cleanup-disabled
VACUUMs. But maybe it's hiding too much information.
2. Have heap_page_prune count, and add to tups_vacuumed, only HOT
tuples that it deleted entirely. The action of replacing a DEAD
root tuple with a dead line pointer doesn't count for anything.
Then also add the count of dead line pointers removed to tups_vacuumed.
Approach #2 is closer to the way we've defined tups_vacuumed up to
now, but I think it'd be more realistic in cases where previous
pruning or index-cleanup-disabled vacuums have left lots of dead
line pointers.
I'm not especially wedded to either of these --- any other ideas?
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, andres@anarazel.de, robertmhaas@gmail.com, sawada.mshk@gmail.com, horiguchi.kyotaro@lab.ntt.co.jp, bossartn@amazon.com, alvherre@2ndquadrant.com
Subject: Re: New vacuum option to do only freezing
In-Reply-To: <7519.1555444815@sss.pgh.pa.us>
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