Re: Making all nbtree entries unique by having heap TIDs participate in comparisons

From: Andrey Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru>
To: Peter Geoghegan <pg(at)bowt(dot)ie>
Cc: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru>
Subject: Re: Making all nbtree entries unique by having heap TIDs participate in comparisons
Date: 2018-10-23 10:35:21
Message-ID: a3b46cc4-8767-a718-a9df-0aa166bd3378@postgrespro.ru
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On 19.10.2018 0:54, Peter Geoghegan wrote:
> I would welcome any theories as to what could be the problem here. I'm
> think that this is fixable, since the picture for the patch is very
> positive, provided you only focus on bgwriter/checkpoint activity and
> on-disk sizes. It seems likely that there is a very specific gap in my
> understanding of how the patch affects buffer cleaning.

I have same problem with background heap & index cleaner (based on your
patch). In this case the bottleneck is WAL-record which I need to write
for each cleaned block and locks which are held during the WAL-record
writing process.
Maybe you will do a test without writing any data to disk?

--
Andrey Lepikhov
Postgres Professional
https://postgrespro.com
The Russian Postgres Company

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