Re: pgstat include expansion

Hi,

On 2026-02-16 17:18:36 +0100, Alvaro Herrera wrote:
> Yeah, I intended not to add access/transam.h here and instead
> forward-declare FullTransactionId, but forgot to actually remove it
> before pushing.  So +1 for what you're doing here with that.  Same with
> relcache.h and most of the other changes you're doing here.

Ah, great.


> I don't think the removal of pg_list.h works terribly well though, as
> that is something that I would expect to be pretty much everywhere, so
> it seems somewhat pointless to try to avoid it in this file.

Yea, I was on the fence about that one.

It does seem pretty crappy that pg_list.h is so widely included and in turn
includes nodes/nodes.h, which then depends on the generated nodetags.h.  For
one it forces an unnecessary rebuild of too much if you add a new node type,
but it also just aesthetically feels wrong.

But avoiding it just here does, as you say, not save very much.



> I think we should in addition remove some includes that were kept during
> recent IWYU hacking "for backwards compatibility", and instead include
> them explicitly wherever they are needed.  The attached does that.

FWIW, the "for backwards compatibility" includes are from prep work towards
shared memory stats. Before that all the stuff in backend_status.h,
backend_progress.h and wait_event.h was in pgstat.h, which was quite
unwieldy. The creation of those headers would have broken a lot of extensions
if we had not provided those backward compat includes from pgstat.h.

I suspect it would still break a fair number of extensions if removed those
includes today. Not sure if the improvement is worth it?  But even if we
decide not to remove the backward compat includes, I think we should fix our
own code to include the right headers directly, rather than rely on doing so
via pgstat.h.


FWIW, your patch that you sent subsequently doesn't seem to apply cleanly for
me? I think it's perhaps based on an older tree, it doesn't know about the
conflict.h include yet...  And it fails to build e.g. due to miscadmin.h
defines around BackendType not being indirectly included in pgstat.h anymore,
but there are many other failures...

Greetings,

Andres Freund