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Skip checkpoints, archiving on idle systems.

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Some background activity (like checkpoints, archive timeout, standby
snapshots) is not supposed to happen on an idle system. Unfortunately
so far it was not easy to determine when a system is idle, which
defeated some of the attempts to avoid redundant activity on an idle
system.

To make that easier, allow to make individual WAL insertions as not
being "important". By checking whether any important activity happened
since the last time an activity was performed, it now is easy to check
whether some action needs to be repeated.

Use the new facility for checkpoints, archive timeout and standby
snapshots.

The lack of a facility causes some issues in older releases, but in my
opinion the consequences (superflous checkpoints / archived segments)
aren't grave enough to warrant backpatching.

Author: Michael Paquier, editorialized by Andres Freund
Reviewed-By: Andres Freund, David Steele, Amit Kapila, Kyotaro HORIGUCHI
Bug: #13685
Discussion:
    https://www.postgresql.org/message-id/20151016203031.3019.72930@wrigleys.postgresql.org
    https://www.postgresql.org/message-id/CAB7nPqQcPqxEM3S735Bd2RzApNqSNJVietAC=6kfkYv_45dKwA@mail.gmail.com
Backpatch: -
This commit is contained in:
Andres Freund
2016-12-22 11:31:50 -08:00
parent 097e41439d
commit 6ef2eba3f5
13 changed files with 173 additions and 77 deletions
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10
doc/src/sgml/config.sgml
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@ -2852,12 +2852,10 @@ include_dir 'conf.d'
parameter is greater than zero, the server will switch to a new
segment file whenever this many seconds have elapsed since the last
segment file switch, and there has been any database activity,
including a single checkpoint. (Increasing
<varname>checkpoint_timeout</> will reduce unnecessary
checkpoints on an idle system.)
Note that archived files that are closed early
due to a forced switch are still the same length as completely full
files. Therefore, it is unwise to use a very short
including a single checkpoint (checkpoints are skipped if there is
no database activity). Note that archived files that are closed
early due to a forced switch are still the same length as completely
full files. Therefore, it is unwise to use a very short
<varname>archive_timeout</> &mdash; it will bloat your archive
storage. <varname>archive_timeout</> settings of a minute or so are
usually reasonable. You should consider using streaming replication,