From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: Isaac Morland <isaac.morland@gmail.com>,
        Alvaro Herrera <alvherre@2ndquadrant.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Our naming of wait events is a disaster.
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Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Thu, 14 May 2020 14:16:29 -0400"
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Date: Thu, 14 May 2020 14:54:42 -0400
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Robert Haas <robertmhaas@gmail.com> writes:
> I tend to prefer that modules register their own tranches rather than
> having a central table someplace, because I like the idea that the
> things that a particular module knows about are contained within its
> own source files and not spread all over the code base. I think that
> we've done rather badly with this in a number of places, lwlock.c
> among them, and I don't like it much.

Well, we could solve this problem very easily by ripping out everything
having to do with wait-state monitoring ... and personally I'd be a lot
in favor of that, because I haven't seen anything about either the
design or documentation of the feature that I thought was very well
done.  However, if you'd like to have wait-state monitoring, and you'd
like the documentation for it to be more useful than "go read the code",
then I don't see any way around the conclusion that there are going to
be centralized lists of the possible wait states.

That being the case, refusing to use a centralized list in the
implementation seems rather pointless; and having some aspects of the
implementation use centralized lists (see the enums in lwlock.h and
elsewhere) while other aspects don't is just schizophrenic.

> In some sense, the lack of naming consistency here is
> a manifestation of an underlying chaos in the code: we've created many
> different ways of waiting for things with many different
> characteristics and little thought to consistency, and this mechanism
> has exposed that underlying problem.

Yeah, agreed.  Nonetheless, now we have a problem.

			regards, tom lane