Re: Improve WALRead() to suck data directly from WAL buffers when possible

At Mon, 12 Dec 2022 11:57:17 +0900 (JST), Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote in
> This patch copies the bleeding edge WAL page without recording the
> (next) insertion point nor checking whether all in-progress insertion
> behind the target LSN have finished. Thus the copied page may have
> holes. That being said, the sequential-reading nature and the fact
> that WAL buffers are zero-initialized may make it work for recovery,
> but I don't think this also works for replication.

Mmm. I'm a bit dim. Recovery doesn't read concurrently-written
records. Please forget about recovery.

> I remember that the one of the advantage of reading the on-memory WAL
> records is that that allows walsender to presend the unwritten
> records. So perhaps we should manage how far the buffer is filled with
> valid content (or how far we can presend) in this feature.

--
Kyotaro Horiguchi
NTT Open Source Software Center