On Wed, Mar 2, 2022 at 7:44 PM Japin Li <japi...@hotmail.com> wrote: > > Hi, hackers > > When I try to change wal_level to minimal and restart the database, it > complains > max_wal_senders > 0. > > 2022-03-03 10:10:16.938 CST [6389] FATAL: WAL streaming (max_wal_senders > > 0) requires wal_level "replica" or "logical" > > However, the documentation about wal_level [1] doesn't mentation this. > How about adding a sentence to describe how to set max_wal_senders when > setting wal_level to minimal? > > [1] https://www.postgresql.org/docs/devel/runtime-config-wal.html > > I would suggest a wording more like:
"A precondition for using minimal WAL is to disable WAL archiving and streaming replication by setting max_wal_senders to 0, and archive_mode to off." While accurate, the phrase "you must set" just doesn't feel right to me. I also don't like how the proposed sentence (either one) is added separately as opposed to being included in the immediately preceding paragraph. While this limited patch is probably sufficient I would suggest trying to work out a slightly larger patch the improves the wording on the entire existing paragraph while incorporating the reference to max_wal_senders. Note, we seem to be missing the documentation of the default setting for archive_mode. In addition, max_wal_senders could also be changed, adding a sentence like: "If setting max_wal_senders to 0 consider also reducing the amount of WAL produced by changing wal_level to minimal." At least insofar as core is concerned without a wal sender the additional wal of replica is not actually able to be leveraged as pg_basebackup will not work (at noted in its own description). David J.
