Re: "as quickly as possible" (was: remove spurious CREATE INDEX CONCURRENTLY wait)

Hi,

On 2020-11-18 18:41:27 -0300, Alvaro Herrera wrote:
> The amount of stuff that this is doing with ProcArrayLock held
> exclusively seems a bit excessive; it sounds like we could copy the
> values we need first, release the lock, and *then* do all that memory
> allocation and string printing -- it's a lock of code for such a
> contended lock.

Yea, that's a good point.

> Anytime a process sees itself as blocked by autovacuum
> and wants to signal it, there's a ProcArrayLock hiccup (I didn't
> actually measure it, but it's at least five function calls).

I'm a bit doubtful it's that important - it's limited in frequency
by deadlock_timeout. But worth improving anyway.

> We could make this more concurrent by copying lock->tag to a local
> variable, releasing the lock, then doing all the string formatting and
> printing. See attached quickly.patch.

Sounds like a plan.

> Now, when this code was written (d7318d43d, 2012), this was a LOG
> message; it was demoted to DEBUG1 later (d8f15c95bec, 2015). I think it
> would be fair to ... remove the message? Or go back to Simon's original
> formulation from commit acac68b2bca, which had this message as DEBUG2
> without any string formatting.

I don't really have an opinion on this.

Greetings,

Andres Freund