At Mon, 07 Feb 2022 13:21:53 +0900 (JST), Kyotaro Horiguchi <horikyota....@gmail.com> wrote in > 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.
I forgot to mentino, but I don't think we need to handle the wrap-around case of the function. regards. -- Kyotaro Horiguchi NTT Open Source Software Center