Re: BUG #15609: synchronous_commit=off insert performance regression with secondary indexes

From: Peter Geoghegan <pg(at)bowt(dot)ie>
To: "Saul, Jean Paolo" <paolo(dot)saul(at)verizonconnect(dot)com>
Cc: Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: BUG #15609: synchronous_commit=off insert performance regression with secondary indexes
Date: 2019-02-11 00:44:39
Message-ID: CAH2-Wznf1uVBguutwrvR+6NcXTKYhagvNOY3-dg9dzcYiu_vKw@mail.gmail.com
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On Sun, Feb 10, 2019 at 3:05 PM Saul, Jean Paolo
<paolo(dot)saul(at)verizonconnect(dot)com> wrote:
> Can anyone please shed some light as to why this works?
> The only thing I could think of is a locking issue with the leaf nodes.

I describe why in the original thread about the problem and my
approach, though it's very low level stuff. See:

https://www.postgresql.org/message-id/flat/CAH2-Wzmf0fvVhU+SSZpGW4Qe9t--j_DmXdX3it5JcdB8FF2EsA(at)mail(dot)gmail(dot)com

> How much testing is required for this to be considered a proper bug?

You haven't really demonstrated a substantial regression across
versions (17361.186258 tps on v11, down from 20137.416962 tps on 9.5),
which is the only way that this could get classified as a bug. It's a
*far* smaller difference than the difference that you show between
otherwise-similar high cardinality and low cardinality indexes. In
general, I'm confused about why you're concerned about v11 in
particular here.

--
Peter Geoghegan

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