Re: Add wait event for CommitDelay

Hi,

> So, my colleague Ants Aasma found that a wait_event is missing for CommitDelay.
> This just looks like it was missed, please enlighten if it is left out intentionally.

I do not know if it was left out intentionally, there are no comments on that
matter.

I am not sure how widely used this GUC is, but from the quick test that I
did using pgench TPC-B workload with 50 clients, it seems useful
since a DBA can set commit_delay too high and you will easily observe
a single backend constantly in this delay which will impact tps.
It's good to show this clearly as a wait event.

As far as the patch goes, It makes sense to put this under "WaitEventTimeout",
but it should be placed after CHECKPOINT_WRITE_DELAY in
alphabetical order, and the description could be improved a bit.
How about? "Waiting for the commit delay before WAL flush."