Re: RFC: replace pg_stat_activity.waiting with something more descriptive

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Cc: Ildus Kurbangaliev <i(dot)kurbangaliev(at)postgrespro(dot)ru>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Subject: Re: RFC: replace pg_stat_activity.waiting with something more descriptive
Date: 2015-08-04 12:15:07
Message-ID: CA+TgmobET4H3aJ1qQfLPy0fU9rTBTQCmUVEbHaokzPP_U_==mQ@mail.gmail.com
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On Tue, Jul 28, 2015 at 3:28 PM, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
> * The patch requires that the LWLOCK_INDIVIDUAL_NAMES array is kept in sync
> with the list of individual locks in lwlock.h. Sooner or later someone will
> add an LWLock and forget to update the names-array. That needs to be made
> less error-prone, so that the names are maintained in the same place as the
> #defines. Perhaps something like rmgrlist.h.

This is a good idea, but it's not easy to do in the style of
rmgrlist.h, because I don't believe there's any way to define a macro
that expands to a preprocessor directive. Attached is a patch that
instead generates the list of macros from a text file, and also
generates an array inside lwlock.c with the lock names that gets used
by the Trace_lwlocks stuff where applicable.

Any objections to this solution to the problem? If not, I'd like to
go ahead and push this much. I can't test the Windows changes
locally, though, so it would be helpful if someone could check that
out.

> * Instead of having LWLOCK_INDIVIDUAL_NAMES to name "individual" locks, how
> about just giving each one of them a separate tranche?

I don't think it's good to split things up to that degree;
standardizing on one name per fixed lwlock and one per tranche
otherwise seems like a good compromise to me.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Attachment Content-Type Size
lwlocknames-v1.patch text/x-patch 14.1 KB

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