Re: archive status ".ready" files may be created too early

The thing I still don't understand about this patch is why we call
RegisterSegmentBoundaryEntry and NotifySegmentsReadyForArchive in
XLogInsertRecord.

My model concept of this would have these routines called only in
XLogFlush / XLogWrite, which are conceptually about transferring data
from in-memory WAL buffers into the on-disk WAL store (pg_xlog files).
As I understand, XLogInsertRecord is about copying bytes from the
high-level operation (heap insert etc) into WAL buffers. So doing the
register/notify dance in both places should be redundant and
unnecessary.

In the NotifySegmentsReadyForArchive() call at the bottom of XLogWrite,
we use flushed=InvalidXLogRecPtr. Why is that? Surely we can use
LogwrtResult.Flush, just like in the other callsite there? (If we're
covering for somebody advancing FlushRecPtr concurrently, I think we
add a comment to explain that. But why do we need to do that in the
first place?)

--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
"The eagle never lost so much time, as
when he submitted to learn of the crow." (William Blake)