Re: WIP: new system catalog pg_wait_event

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: "Drouvot, Bertrand" <bertranddrouvot(dot)pg(at)gmail(dot)com>
Cc: Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, tgl(at)sss(dot)pgh(dot)pa(dot)us, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: WIP: new system catalog pg_wait_event
Date: 2023-08-14 04:37:14
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On Thu, Aug 10, 2023 at 08:09:34PM +0200, Drouvot, Bertrand wrote:
> Agree that's worth it given the fact that iterating one more time is not that
> costly here.

I have reviewed v4, and finished by putting my hands on it to see what
I could do.

+ printf $wc "\telement = (wait_event_element *) palloc(sizeof(wait_event_element));\n";
+ printf $wc "\telement->wait_event_type = \"%s\";\n", $last;
+ printf $wc "\telement->wait_event_name = \"%s\";\n", $wev->[1];
+ printf $wc "\telement->wait_event_description = \"%s\";\n\n", $new_desc;
+ printf $wc "\twait_event = lappend(wait_event, element);\n\n";
+ }

This is simpler than the previous versions, still I am not much a fan
of implying the use of a list and these pallocs. There are two things
that we could do:
- Hide that behind a macro defined in wait_event_funcs.c.
- Feed the data generated here into a static structure, like:
+static const struct
+ const char *type;
+ const char *name;
+ const char *description;

After experimenting with both, I've found the latter a tad cleaner, so
the attached version does that.

+ <structfield>description</structfield> <type>texte</type>
This one was difficult to see..

I am not sure that "pg_wait_event" is a good idea for the name if the
new view. How about "pg_wait_events" instead, in plural form? There
is more than one wait event listed.

One log entry in has missed the addition of a reference to

And.. src/backend/Makefile missed two updates for maintainer-clean & co,

One thing that the patch is still missing is the handling of custom
wait events for extensions. So this still requires more code. I was
thinking about listed these events as:
- Type: "Extension"
- Name: What a module has registered.
- Description: "Custom wait event \"%Name%\" defined by extension".

For now I am attaching a v5.

Attachment Content-Type Size
v5-0001-pg_wait_event.patch text/x-diff 17.8 KB

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