Re: Fix lwlock.c and wait_event_names.txt discrepancy

Hi,

On Wed, Jul 16, 2025 at 01:33:07PM +0200, Álvaro Herrera wrote:
> On 2025-Jul-16, Michael Paquier wrote:
>
> > On Wed, Jul 16, 2025 at 09:30:31AM +0000, Bertrand Drouvot wrote:
>
> > > Indeed, the wait event names are MultixactOffsetSLRU and MultixactMemberSLRU in
> > > the C file but MultiXactOffsetSLRU and MultiXactMemberSLRU in the text file.
> > >
> > > That breaks joins between pg_stat_activity and pg_wait_events on the wait
> > > event name. PFA a patch to fix those (I'm not able to find other discrepancy
> > > with the "automated" work I'm doing in [1], so I'm confident there is no others).
> >
> > This is in the same line as 08b9b9e043bb, down to v17. For
> > 08b9b9e043bb, we were lucky enough to not be in GA, would people mind
> > to sneak this lwlock tranche name change in v17?
>
> I don't. These names are unlikely to be anywhere other than in the
> output of queries for any length of time, so if we change them now,
> nothing will break permanently. I grant that there might be small
> temporary breakage if somebody is storing wait event samples or similar,
> but I doubt it'll be a problem to change it. Long-term lack of
> joinability between pg_stat_activity and pg_wait_events in the 17 branch
> would likely be a bigger problem.

+1

As a way to prevent this to occur we might want to add extra input file(s)
parameter to generate-wait_event_types.pl (as proposed in [1]).

[1]: https://www.postgresql.org/message-id/flat/aDQdDhcwMHjZRhSV%40ip-10-97-1-34.eu-west-3.compute.internal

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
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