Re: Need help understanding pg_locks

Florian Pflug <fgp(at)phlo(dot)org> writes:
> On Jul11, 2011, at 17:11 , Tom Lane wrote:
>> Yeah, I think this patch is going in the wrong direction altogether.
>> It would be better to modify the description of virtualtransaction
>> and pid to say that those are the "locking" entity.

> Hm, we already kinda of say that. Both descriptions include the phrase
> "... holding or awaiting this lock.". The column "mode" says
> "... held or desired by this process", which I guess is similar enough
> to make it clear that these are related.

> Its the columns which refer to the locked object which simply say
> "object", and thus leave it open if that means locked or a locking.

> Could we split that table in two parts, one for the fields referring
> to the locked object and one for the locking entity, or does that depart
> too far from the way we document other system catalogs and views?

Then you'd have to join them, which would not be an improvement from
anybody's standpoint.

Maybe we could just add a paragraph above the "pg_locks Columns" table
that says explicitly that virtualtransaction and pid describe the entity
holding or awaiting the lock, and the others describe the object being
locked? Any way you slice it, putting this information into the
per-column table is going to be repetitive.

regards, tom lane