| From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Noah Misch <noah(at)leadboat(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Antonin Houska <ah(at)cybertec(dot)at>, Srinath Reddy Sadipiralla <srinath2133(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Mihail Nikalayeu <mihailnikalayeu(at)gmail(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Robert Treat <rob(at)xzilla(dot)net> |
| Subject: | Re: Adding REPACK [concurrently] |
| Date: | 2026-04-06 21:59:59 |
| Message-ID: | 202604062121.ijkompbo4ezj@alvherre.pgsql |
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| Lists: | pgsql-hackers |
On 2026-Apr-06, Andres Freund wrote:
> I just saw this got committed and wanted to briefly play with it. It works
> nicely!
Yeah, I have to say that Antonin did a great job here.
> Except that at first I tried this in a debugging build, and was briefly rather
> dismayed by the performance. It was really slow. But it's not really related
> to repack / the patches here.
>
> In that config, the assert single-handled increases the time for a repack by
> 35% or so.
Yeah, I saw it was kinda sluggish, but wow, I didn't see *that* much
overhead.
> It's totally valid to not have done so initially, this is a quite complicated
> feature:
>
> I saw this is using individual heap_insert()s during the
> heapam_relation_copy_for_cluster(). Doing individual WAL logged inserts isn't
> exactly cheap or efficient from a WAL volume perspective...
>
> Is there anything other than round tuits preventing us from using
> multi_insert?
>
> That actually would also reduce the cost in the REPACK decoding worker, due to
> having to parse far fewer WAL records.
Nope, not really ... but I don't have any :-(
--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
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