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From: Alvaro Herrera <[email protected]>
To: Andres Freund <[email protected]>
Cc: Noah Misch <[email protected]>
Cc: vignesh C <[email protected]>
Cc: Antonin Houska <[email protected]>
Cc: Srinath Reddy Sadipiralla <[email protected]>
Cc: Amit Kapila <[email protected]>
Cc: Mihail Nikalayeu <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: Pg Hackers <[email protected]>
Cc: Robert Treat <[email protected]>
Subject: Re: Adding REPACK [concurrently]
Date: Mon, 6 Apr 2026 23:59:59 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <pbqm52nsviwojptiszg2g6pqntbhnhaotbxshiysnensshnuv5@v6pmney4jror>

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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