| From: | p(dot)luzanov(at)postgrespro(dot)ru |
|---|---|
| To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
| Cc: | pluzanov(at)postgrespro(dot)ru, pgsql-docs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: max_wal_size |
| Date: | 2020-05-27 16:17:23 |
| Message-ID: | 92491c6d07a3216ef2caee8ef55c02b5@postgrespro.ru |
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| Thread: | |
| Lists: | pgsql-docs |
David,
> This setting is the indirect means to ensure that the WAL directory
> doesn't get too large by forcing a checkpoint thus allowing the
> corresponding WAL to be removed.
This is a soft limit, ok.
But the question is a little different.
Suppose we have: version >= 11, no replication slots, archive_mode =
off.
Checkpoint_timeout is big enough, so checkpoints triggered only by
max_wal_size (1GB).
checkpoint_completion_target = 1.
What size of WAL files will be generated between checkpoints?
1GB or 0.5GB?
As I understand the description of max_wal_size(Maximum size to let the
WAL grow to between automatic WAL checkpoints), the answer is 1GB.
But it seems that the right answer is 0.5GB.
-----
Pavel Luzanov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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