Thread: max_wal_size
Hello,
About parameter max_wal_size the documentation says: "Maximum size to let the WAL grow to between automatic WAL checkpoints."
Is it correct?
The size between automatic WAL checkpoints or the size of all WAL files in the pg_wal directory?
About parameter max_wal_size the documentation says: "Maximum size to let the WAL grow to between automatic WAL checkpoints."
Is it correct?
The size between automatic WAL checkpoints or the size of all WAL files in the pg_wal directory?
----- Pavel Luzanov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
Am 27.05.20 um 12:11 schrieb Pavel Luzanov: > Hello, > > About parameter max_wal_size the documentation > <https://www.postgresql.org/docs/current/runtime-config-wal.html#GUC-MAX-WAL-SIZE> > says: "Maximum size to let the WAL grow to between automatic WAL > checkpoints." > Is it correct? > > The size between automatic WAL checkpoints or the size of all WAL > files in the pg_wal directory? size between checkpoints, size of all wal's can be higher, see wal_keep_segments. Regards, Andreas -- 2ndQuadrant - The PostgreSQL Support Company. www.2ndQuadrant.com
Andreas,
Hm, I also thought, but after looking at the source, it seems like this is a restriction on all files in pg_wal.
size between checkpoints, size of all wal's can be higher, see wal_keep_segments.
Hm, I also thought, but after looking at the source, it seems like this is a restriction on all files in pg_wal.
----- Pavel Luzanov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
On 27.05.2020 13:16, Andreas Kretschmer wrote: > > Am 27.05.20 um 12:11 schrieb Pavel Luzanov: >> Hello, >> >> About parameter max_wal_size the documentation >> <https://www.postgresql.org/docs/current/runtime-config-wal.html#GUC-MAX-WAL-SIZE> >> says: "Maximum size to let the WAL grow to between automatic WAL >> checkpoints." >> Is it correct? >> >> The size between automatic WAL checkpoints or the size of all WAL >> files in the pg_wal directory? > > size between checkpoints, size of all wal's can be higher, see > wal_keep_segments. > It is clear that total size can be higher due to wal_keep_segments, replications slots, archive_command etc. But does max_wal_size relate to the (a) two subsequent checkpoints (as you may read the wording in the docs) or (b) to the past completed checkpoint AND the current yet-uncompleted checkpoint (which together may be up to TWO checkpoint intervals)? If I read CalculateCheckpointSegments() in xlog.c correctly, the answer is (b), and hence the documentation is misleading. Regards, Egor.