> But even then, we don't actually have to track the *names* of the
> files that have changed, just their RelFileNodes, since there's a
> mapping function from the RelFileNode to the filename.
Right. I have noticed that too and have made changes to my
implementaion.
BTW, you need to track the block number as well. Files > 1GB may be
splitted into separate files (segments).
> > Of course, if there are lots of files, sync() may be faster than
> > opening/fsync/closing all those files.
>
> This is true, and is something I hadn't actually thought of. So it
> sounds like some testing would be in order.
I regard the difference between sync() and fsync() does not affect too
much to the whole performance. Checkpoint process is performed as a
separate process and the fsync() part of checkpoint does nothing with
WAL, that means other backend processes, busy with WAL IO will
not be bothered.
--
Tatsuo Ishii
