Antonin Houska <ah@cybertec.at> wrote:
> Andres Freund <andres@anarazel.de> wrote:
> > But I'm not sure it's quite the right idea. I'm not sure I fully
> > understand the design of 0dc8ead46, but it looks to me like it's
> > intended to allow users of the interface to have different ways of
> > opening files. If we just close() the fd that'd be a bit more limited.
>
> It should have allowed users to have different ways to *locate the segment*
> file. The WALSegmentOpen callback could actually return file path instead of
> the file descriptor and let WALRead() perform the opening/closing, but then
> the WALRead function would need to be aware whether it is executing in backend
> or in frontend (so it can use the correct function to open/close the file).
Well, #ifdef FRONTEND can be used to distinguish the caller of
WALRead(). However now that I tried to adjust the API, I see that
pg_waldump.c:WALDumpOpenSegment uses specific logic to open the file. So if
the callback only returned the file name, there would be no suitable place for
the things that WALDumpOpenSegment does.
--
Antonin Houska
Web: https://www.cybertec-postgresql.com
