These settings control the behavior of the autovacuum feature. Refer to Section 24.1.6 for more information. Note that many of these settings can be overridden on a per-table basis; see Storage Parameters.
autovacuum (boolean)
Controls whether the server should run the
autovacuum launcher daemon. This is on by default; however,
track_counts must also be enabled for
autovacuum to work.
This parameter can only be set in the postgresql.conf
file or on the server command line; however, autovacuuming can be
disabled for individual tables by changing table storage parameters.
Note that even when this parameter is disabled, the system will launch autovacuum processes if necessary to prevent transaction ID wraparound. See Section 24.1.5 for more information.
log_autovacuum_min_duration (integer)
Causes each action executed by autovacuum to be logged if it ran for at
least the specified amount of time. Setting this to zero logs
all autovacuum actions. -1 (the default) disables
logging autovacuum actions.
If this value is specified without units, it is taken as milliseconds.
For example, if you set this to
250ms then all automatic vacuums and analyzes that run
250ms or longer will be logged. In addition, when this parameter is
set to any value other than -1, a message will be
logged if an autovacuum action is skipped due to a conflicting lock or a
concurrently dropped relation. Enabling this parameter can be helpful
in tracking autovacuum activity. This parameter can only be set in
the postgresql.conf file or on the server command line;
but the setting can be overridden for individual tables by
changing table storage parameters.
autovacuum_max_workers (integer)
Specifies the maximum number of autovacuum processes (other than the autovacuum launcher) that may be running at any one time. The default is three. This parameter can only be set at server start.
autovacuum_naptime (integer)
Specifies the minimum delay between autovacuum runs on any given
database. In each round the daemon examines the
database and issues VACUUM and ANALYZE commands
as needed for tables in that database.
If this value is specified without units, it is taken as seconds.
The default is one minute (1min).
This parameter can only be set in the postgresql.conf
file or on the server command line.
autovacuum_vacuum_threshold (integer)
Specifies the minimum number of updated or deleted tuples needed
to trigger a VACUUM in any one table.
The default is 50 tuples.
This parameter can only be set in the postgresql.conf
file or on the server command line;
but the setting can be overridden for individual tables by
changing table storage parameters.
autovacuum_analyze_threshold (integer)
Specifies the minimum number of inserted, updated or deleted tuples
needed to trigger an ANALYZE in any one table.
The default is 50 tuples.
This parameter can only be set in the postgresql.conf
file or on the server command line;
but the setting can be overridden for individual tables by
changing table storage parameters.
autovacuum_vacuum_scale_factor (floating point)
Specifies a fraction of the table size to add to
autovacuum_vacuum_threshold
when deciding whether to trigger a VACUUM.
The default is 0.2 (20% of table size).
This parameter can only be set in the postgresql.conf
file or on the server command line;
but the setting can be overridden for individual tables by
changing table storage parameters.
autovacuum_analyze_scale_factor (floating point)
Specifies a fraction of the table size to add to
autovacuum_analyze_threshold
when deciding whether to trigger an ANALYZE.
The default is 0.1 (10% of table size).
This parameter can only be set in the postgresql.conf
file or on the server command line;
but the setting can be overridden for individual tables by
changing table storage parameters.
autovacuum_freeze_max_age (integer)
Specifies the maximum age (in transactions) that a table's
pg_class.relfrozenxid field can
attain before a VACUUM operation is forced
to prevent transaction ID wraparound within the table.
Note that the system will launch autovacuum processes to
prevent wraparound even when autovacuum is otherwise disabled.
Vacuum also allows removal of old files from the
pg_xact subdirectory, which is why the default
is a relatively low 200 million transactions.
This parameter can only be set at server start, but the setting
can be reduced for individual tables by
changing table storage parameters.
For more information see Section 24.1.5.
autovacuum_multixact_freeze_max_age (integer)
Specifies the maximum age (in multixacts) that a table's
pg_class.relminmxid field can
attain before a VACUUM operation is forced to
prevent multixact ID wraparound within the table.
Note that the system will launch autovacuum processes to
prevent wraparound even when autovacuum is otherwise disabled.
Vacuuming multixacts also allows removal of old files from the
pg_multixact/members and pg_multixact/offsets
subdirectories, which is why the default is a relatively low
400 million multixacts.
This parameter can only be set at server start, but the setting can
be reduced for individual tables by changing table storage parameters.
For more information see Section 24.1.5.1.
autovacuum_vacuum_cost_delay (floating point)
Specifies the cost delay value that will be used in automatic
VACUUM operations. If -1 is specified, the regular
vacuum_cost_delay value will be used.
If this value is specified without units, it is taken as milliseconds.
The default value is 2 milliseconds.
This parameter can only be set in the postgresql.conf
file or on the server command line;
but the setting can be overridden for individual tables by
changing table storage parameters.
autovacuum_vacuum_cost_limit (integer)
Specifies the cost limit value that will be used in automatic
VACUUM operations. If -1 is specified (which is the
default), the regular
vacuum_cost_limit value will be used. Note that
the value is distributed proportionally among the running autovacuum
workers, if there is more than one, so that the sum of the limits for
each worker does not exceed the value of this variable.
This parameter can only be set in the postgresql.conf
file or on the server command line;
but the setting can be overridden for individual tables by
changing table storage parameters.