Feedback-ID: ie3de48e3:Fastmail
Date: Thu, 17 Sep 2026 16:55:44 +0200
From: =?utf-8?Q?=C3=81lvaro?= Herrera <alvherre@kurilemu.de>
To: Manuel Reyes Bravo <manuelreyesbravo@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	Fujii Masao <masao.fujii@gmail.com>, Adam Lee <adam8157@gmail.com>
Subject: Re: Add a test for index_rebuild_count of REPACK (CONCURRENTLY)
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Hello,

On 2026-Sep-16, Manuel Reyes Bravo wrote:

> I would like to work on the framework for v20, if nobody else is.

Sounds good.

> Some facts that make it look tractable:
> 
> - Every write to st_progress_param goes through backend_progress.c
>   (pgstat_progress_update_param, _incr_param, _parallel_incr_param,
>   _update_multi_param, plus start/end_command).  There are 163 calls in
>   23 files, and none of them writes the array directly, so one hook
>   there sees every update.

Yep.

> - There is precedent for the switch in the DEVELOPER_OPTIONS trace_*
>   settings (trace_locks, trace_notify, trace_sort, ...).

I think those are all pretty archaic, so I wouldn't necessarily base a
design on them.

> Before writing anything, three questions, so that I build what you have
> in mind:
> 
> 1. A runtime developer setting (say trace_progress, like trace_notify)
>    or something compiled in only for debug builds (like LOCK_DEBUG
>    around trace_locks)?

I think a compile option is enough.  We'll want a buildfarm animal that
runs with that option set, but things set up in such a way that the
(limited amount of) debug code is compiled out for regular developer
builds, so that this doesn't cause "meson test" to be any slower.

> 2. Should tests read the lines from the server log in TAP tests, or
>    from the client with client_min_messages in the regression suite?
>    Counters such as blocks scanned vary between runs, so I assume a test
>    would match phases and selected counters rather than every line.

No opinion on this.  Maybe a good frame would be a TAP test that runs
REPACK/COPY/etc and then reads the debug output to see if the order of
phase switching is from A to B to C, and that block numbers in column
such-and-such are monotonically increasing within one phase, and that
they get back to 0 when changing to phase X, etc.

> 3. One line per call, or only when a value actually changes?

I think emitting a line when nothing has changed would be pointless
noise.

> The first users would be VACUUM and REPACK, including the two
> index_rebuild_count cases from this week.

Sure, as long as it's not restricted to only cover them.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/