At Fri, 4 Feb 2022 14:50:57 -0800, Nathan Bossart <nathandboss...@gmail.com> wrote in > On Fri, Feb 04, 2022 at 09:17:54AM -0500, Robert Haas wrote: > > On Fri, Feb 4, 2022 at 9:05 AM Ashutosh Bapat > > <ashutosh.bapat....@gmail.com> wrote: > >> And it gives some surprising results as well > >> --- > >> #select pg_walfile_name('0/0'::pg_lsn); > >> pg_walfile_name > >> -------------------------- > >> 00000001FFFFFFFF000000FF > >> (1 row) > >> ---- > > > > Yeah, that seems wrong. > > It looks like it's been this way for a while (704ddaa). > pg_walfile_name_offset() has the following comment: > > * Note that a location exactly at a segment boundary is taken to be in > * the previous segment. This is usually the right thing, since the > * expected usage is to determine which xlog file(s) are ready to archive. > > I see a couple of discussions about this as well [0] [1]. > > [0] > https://www.postgresql.org/message-id/flat/1154384790.3226.21.camel%40localhost.localdomain > [1] > https://www.postgresql.org/message-id/flat/15952.1154827205%40sss.pgh.pa.us
Yes, its the deliberate choice of design, or a kind of questionable-but-unoverturnable decision. I think there are many external tools conscious of this behavior. It is also described in the documentation. https://www.postgresql.org/docs/current/functions-admin.html > When the given write-ahead log location is exactly at a write-ahead > log file boundary, both these functions return the name of the > preceding write-ahead log file. This is usually the desired behavior > for managing write-ahead log archiving behavior, since the preceding > file is the last one that currently needs to be archived. regards. -- Kyotaro Horiguchi NTT Open Source Software Center