| From: | Michael Paquier <michael(at)paquier(dot)xyz> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, James Coleman <jtc331(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: remove spurious CREATE INDEX CONCURRENTLY wait |
| Date: | 2020-11-10 02:44:23 |
| Message-ID: | 20201110024423.GG1887@paquier.xyz |
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| Lists: | pgsql-hackers |
On Mon, Nov 09, 2020 at 11:31:15PM -0300, Alvaro Herrera wrote:
> Yeah ... it would be much better if we can make it use atomics instead.
> Currently it's an uint8, and in PGPROC itself it's probably not a big
> deal to enlarge that, but I fear that quadrupling the size of the
> mirroring array in PROC_HDR might be bad for performance. However,
> maybe if we use atomics to access it, then we don't need to mirror it
> anymore? That would need some benchmarking of GetSnapshotData.
Hmm. If you worry about the performance impact here, it is possible
to do a small performance test without this patch. vacuum_rel() sets
the flag for a non-full VACUUM, so with one backend running a manual
VACUUM in loop on an empty relation could apply some pressure on any
benchmark, even a simple pgbench.
--
Michael
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