Alfred Perlstein <bright@wintelcom.net> writes:
> postgresql has 3 files open (a, b, c), so will the syncer.
The syncer must have all the files open that are open in any backend?
What happens when it runs into the FDs-per-process limit?
> backend 1 completes a request, communicates to the syncer that a flush
> is needed.
> syncer starts by fsync'ing 'a'
> backend 2 completes a request, communicates to the syncer
> syncer continues with 'b' then 'c'
> syncer responds to backend 1 that it's safe to proceed.
> syncer fsyncs 'a' again
> syncer responds to backend 2 that it's all completed.
> effectively the fsync of 'b' and 'c' have been batched.
And it's safe to update pg_log when?
I'm failing to see where the advantage is compared to the backends
issuing their own fsyncs...
regards, tom lane