| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Jakub Wartak <jakub(dot)wartak(at)enterprisedb(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Peter Eisentraut <peter(at)eisentraut(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Performance degradation on concurrent COPY into a single relation in PG16. |
| Date: | 2023-09-25 19:48:30 |
| Message-ID: | 20230925194830.fr2fn43h63w5fyyu@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2023-09-25 15:42:26 -0400, Tom Lane wrote:
> I just did a git bisect run to discover when the failure documented
> in bug #18130 [1] started. And the answer is commit 82a4edabd.
> Now, it's pretty obvious that that commit didn't in itself cause
> problems like this:
>
> postgres=# \copy test from 'bug18130.csv' csv
> ERROR: could not read block 5 in file "base/5/17005": read only 0 of 8192 bytes
> CONTEXT: COPY test, line 472: "0,185647715,222655,489637,2,2023-07-31,9100.0000000,302110385,2023-07-30 14:16:36.750981+00,14026347..."
Ugh.
> IMO there must be some very nasty bug lurking in the new
> multiple-block extension logic, that happens to be exposed by this
> test case with 82a4edabd's adjustments to the when-to-extend choices
> but wasn't before that.
> To save other people the trouble of extracting the in-line data
> in the bug submission, I've attached the test files I was using.
Thanks, looking at this now.
> The DDL is simplified slightly from what was submitted. I'm not
> entirely sure why a no-op trigger is needed to provoke the bug...
A trigger might prevent using the multi-insert API, which would lead to
different execution paths...
Greetings,
Andres Freund
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