Re: WALWriteLock contention

Robert Haas <robertmhaas@gmail.com> writes:
> WALWriteLock contention is measurable on some workloads.  In studying
> the problem briefly, a couple of questions emerged:

> 1. Doesn't it suck to rewrite an entire 8kB block every time, instead
> of only the new bytes (and maybe a few bytes following that to spoil
> any old data that might be there)?

It does, but it's not clear how to avoid torn-write conditions without
that.

> 2. I don't really understand why WALWriteLock is set up to prohibit
> two backends from flushing WAL at the same time.  That seems
> unnecessary.

Hm, perhaps so.
        regards, tom lane