<para>
These settings control the behavior of the <firstterm>autovacuum</>
- feature. Refer to <xref linkend="autovacuum"> for
- more information.
+ feature. Refer to <xref linkend="autovacuum"> for more information.
+ Note that many of these settings can be overridden on a per-table
+ basis; see <xref linkend="sql-createtable-storage-parameters"
+ endterm="sql-createtable-storage-parameters-title">.
</para>
<variablelist>
<xref linkend="guc-track-counts"> must also be enabled for
autovacuum to work.
This parameter can only be set in the <filename>postgresql.conf</>
- file or on the server command line.
+ file or on the server command line; however, autovacuuming can be
+ disabled for individual tables by changing table storage parameters.
</para>
<para>
Note that even when this parameter is disabled, the system
set to any value other than <literal>-1</literal>, a message will be
logged if an autovacuum action is skipped due to the existence of a
conflicting lock. Enabling this parameter can be helpful
- in tracking autovacuum activity. This setting can only be set in
- the <filename>postgresql.conf</> file or on the server command line.
+ in tracking autovacuum activity. This parameter can only be set in
+ the <filename>postgresql.conf</> file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
</para>
</listitem>
</varlistentry>
<listitem>
<para>
Specifies the maximum number of autovacuum processes (other than the
- autovacuum launcher) which may be running at any one time. The default
+ autovacuum launcher) that may be running at any one time. The default
is three. This parameter can only be set at server start.
</para>
</listitem>
to trigger a <command>VACUUM</> in any one table.
The default is 50 tuples.
This parameter can only be set in the <filename>postgresql.conf</>
- file or on the server command line.
- This setting can be overridden for individual tables by
- changing storage parameters.
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
</para>
</listitem>
</varlistentry>
needed to trigger an <command>ANALYZE</> in any one table.
The default is 50 tuples.
This parameter can only be set in the <filename>postgresql.conf</>
- file or on the server command line.
- This setting can be overridden for individual tables by
- changing storage parameters.
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
</para>
</listitem>
</varlistentry>
when deciding whether to trigger a <command>VACUUM</>.
The default is 0.2 (20% of table size).
This parameter can only be set in the <filename>postgresql.conf</>
- file or on the server command line.
- This setting can be overridden for individual tables by
- changing storage parameters.
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
</para>
</listitem>
</varlistentry>
when deciding whether to trigger an <command>ANALYZE</>.
The default is 0.1 (10% of table size).
This parameter can only be set in the <filename>postgresql.conf</>
- file or on the server command line.
- This setting can be overridden for individual tables by
- changing storage parameters.
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
</para>
</listitem>
</varlistentry>
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 storage parameters.
+ changing table storage parameters.
For more information see <xref linkend="vacuum-for-wraparound">.
</para>
</listitem>
<filename>pg_multixact/members</> and <filename>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 storage parameters.
+ 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 <xref linkend="vacuum-for-multixact-wraparound">.
</para>
</listitem>
<xref linkend="guc-vacuum-cost-delay"> value will be used.
The default value is 20 milliseconds.
This parameter can only be set in the <filename>postgresql.conf</>
- file or on the server command line.
- This setting can be overridden for individual tables by
- changing storage parameters.
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
</para>
</listitem>
</varlistentry>
default), the regular
<xref linkend="guc-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 of
- each worker never exceeds the limit on this variable.
+ 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 <filename>postgresql.conf</>
- file or on the server command line.
- This setting can be overridden for individual tables by
- changing storage parameters.
+ file or on the server command line;
+ but the setting can be overridden for individual tables by
+ changing table storage parameters.
</para>
</listitem>
</varlistentry>
the entries in it to the main GIN data structure in bulk.
The default is four megabytes (<literal>4MB</>). This setting
can be overridden for individual GIN indexes by changing
- storage parameters.
+ index storage parameters.
See <xref linkend="gin-fast-update"> and <xref linkend="gin-tips">
for more information.
</para>
the next database will be processed as soon as the first worker finishes.
Each worker process will check each table within its database and
execute <command>VACUUM</> and/or <command>ANALYZE</> as needed.
- <varname>log_autovacuum_min_duration</varname> can be used to monitor
- autovacuum activity.
+ <xref linkend="guc-log-autovacuum-min-duration"> can be set to monitor
+ autovacuum workers' activity.
</para>
<para>
If several large tables all become eligible for vacuuming in a short
amount of time, all autovacuum workers might become occupied with
vacuuming those tables for a long period. This would result
- in other tables and databases not being vacuumed until a worker became
+ in other tables and databases not being vacuumed until a worker becomes
available. There is no limit on how many workers might be in a
single database, but workers do try to avoid repeating work that has
already been done by other workers. Note that the number of running
<para>
The default thresholds and scale factors are taken from
<filename>postgresql.conf</filename>, but it is possible to override them
- on a table-by-table basis; see
+ (and many other autovacuum control parameters) on a per-table basis; see
<xref linkend="sql-createtable-storage-parameters"
endterm="sql-createtable-storage-parameters-title"> for more information.
- If a setting
- has been changed via storage parameters, that value is used; otherwise the
- global settings are used. See <xref linkend="runtime-config-autovacuum"> for
- more details on the global settings.
- </para>
-
- <para>
- Besides the base threshold values and scale factors, there are six
- more autovacuum parameters that can be set for each table via
- storage parameters.
- The first parameter, <literal>autovacuum_enabled</>,
- can be set to <literal>false</literal> to instruct the autovacuum daemon
- to skip that particular table entirely. In this case
- autovacuum will only touch the table if it must do so
- to prevent transaction ID wraparound.
- Another two parameters,
- <varname>autovacuum_vacuum_cost_delay</> and
- <varname>autovacuum_vacuum_cost_limit</>, are used to set
- table-specific values for the cost-based vacuum delay feature
- (see <xref linkend="runtime-config-resource-vacuum-cost">).
- <varname>autovacuum_freeze_min_age</>,
- <varname>autovacuum_freeze_max_age</> and
- <varname>autovacuum_freeze_table_age</> are used to set
- values for <xref linkend="guc-vacuum-freeze-min-age">,
- <xref linkend="guc-autovacuum-freeze-max-age"> and
- <xref linkend="guc-vacuum-freeze-table-age"> respectively.
- </para>
-
- <para>
- When multiple workers are running, the cost delay parameters are
+ If a setting has been changed via a table's storage parameters, that value
+ is used when processing that table; otherwise the global settings are
+ used. See <xref linkend="runtime-config-autovacuum"> for more details on
+ the global settings.
+ </para>
+
+ <para>
+ When multiple workers are running, the autovacuum cost delay parameters
+ (see <xref linkend="runtime-config-resource-vacuum-cost">) are
<quote>balanced</quote> among all the running workers, so that the
total I/O impact on the system is the same regardless of the number
of workers actually running. However, any workers processing tables whose
- <literal>autovacuum_vacuum_cost_delay</> or
- <literal>autovacuum_vacuum_cost_limit</> have been set are not considered
- in the balancing algorithm.
+ per-table <literal>autovacuum_vacuum_cost_delay</> or
+ <literal>autovacuum_vacuum_cost_limit</> storage parameters have been set
+ are not considered in the balancing algorithm.
</para>
</sect2>
</sect1>
Storage parameters for
indexes are documented in <xref linkend="SQL-CREATEINDEX">.
The storage parameters currently
- available for tables are listed below. For each parameter, unless noted,
- there is an additional parameter with the same name prefixed with
- <literal>toast.</literal>, which can be used to control the behavior of the
+ available for tables are listed below. For many of these parameters, as
+ shown, there is an additional parameter with the same name prefixed with
+ <literal>toast.</literal>, which controls the behavior of the
table's secondary <acronym>TOAST</> table, if any
(see <xref linkend="storage-toast"> for more information about TOAST).
- Note that the TOAST table uses the parameter values defined for
- the main table, for each parameter applicable to TOAST tables and
- for which no value is set in the TOAST table itself.
+ If a table parameter value is set and the
+ equivalent <literal>toast.</literal> parameter is not, the TOAST table
+ will use the table's parameter value.
</para>
<variablelist>
<term><literal>autovacuum_enabled</>, <literal>toast.autovacuum_enabled</literal> (<type>boolean</>)</term>
<listitem>
<para>
- Enables or disables the autovacuum daemon on a particular table.
- If true, the autovacuum daemon will initiate a <command>VACUUM</> operation
- on a particular table when the number of updated or deleted tuples exceeds
- <literal>autovacuum_vacuum_threshold</> plus
- <literal>autovacuum_vacuum_scale_factor</> times the number of live tuples
- currently estimated to be in the relation.
- Similarly, it will initiate an <command>ANALYZE</> operation when the
- number of inserted, updated or deleted tuples exceeds
- <literal>autovacuum_analyze_threshold</> plus
- <literal>autovacuum_analyze_scale_factor</> times the number of live tuples
- currently estimated to be in the relation.
+ Enables or disables the autovacuum daemon for a particular table.
+ If true, the autovacuum daemon will perform automatic <command>VACUUM</>
+ and/or <command>ANALYZE</> operations on this table following the rules
+ discussed in <xref linkend="autovacuum">.
If false, this table will not be autovacuumed, except to prevent
- transaction Id wraparound. See <xref linkend="vacuum-for-wraparound"> for
+ transaction ID wraparound. See <xref linkend="vacuum-for-wraparound"> for
more about wraparound prevention.
- Observe that this variable inherits its value from the <xref
- linkend="guc-autovacuum"> setting.
+ Note that the autovacuum daemon does not run at all (except to prevent
+ transaction ID wraparound) if the <xref linkend="guc-autovacuum">
+ parameter is false; setting individual tables' storage parameters does
+ not override that. Therefore there is seldom much point in explicitly
+ setting this storage parameter to <literal>true</>, only
+ to <literal>false</>.
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_vacuum_threshold</>, <literal>toast.autovacuum_vacuum_threshold</literal> (<type>integer</>)</term>
<listitem>
<para>
- Minimum number of updated or deleted tuples before initiate a
- <command>VACUUM</> operation on a particular table.
+ Per-table value for <xref linkend="guc-autovacuum-vacuum-threshold">
+ parameter.
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_vacuum_scale_factor</>, <literal>toast.autovacuum_vacuum_scale_factor</literal> (<type>float4</>)</term>
<listitem>
<para>
- Multiplier for <structfield>reltuples</> to add to
- <literal>autovacuum_vacuum_threshold</>.
+ Per-table value for <xref linkend="guc-autovacuum-vacuum-scale-factor">
+ parameter.
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_analyze_threshold</> (<type>integer</>)</term>
<listitem>
<para>
- Minimum number of inserted, updated, or deleted tuples before initiate an
- <command>ANALYZE</> operation on a particular table.
+ Per-table value for <xref linkend="guc-autovacuum-analyze-threshold">
+ parameter.
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_analyze_scale_factor</> (<type>float4</>)</term>
<listitem>
<para>
- Multiplier for <structfield>reltuples</> to add to
- <literal>autovacuum_analyze_threshold</>.
+ Per-table value for <xref linkend="guc-autovacuum-analyze-scale-factor">
+ parameter.
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_vacuum_cost_delay</>, <literal>toast.autovacuum_vacuum_cost_delay</literal> (<type>integer</>)</term>
<listitem>
<para>
- Custom <xref linkend="guc-autovacuum-vacuum-cost-delay"> parameter.
+ Per-table value for <xref linkend="guc-autovacuum-vacuum-cost-delay">
+ parameter.
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_vacuum_cost_limit</>, <literal>toast.autovacuum_vacuum_cost_limit</literal> (<type>integer</>)</term>
<listitem>
<para>
- Custom <xref linkend="guc-autovacuum-vacuum-cost-limit"> parameter.
+ Per-table value for <xref linkend="guc-autovacuum-vacuum-cost-limit">
+ parameter.
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_freeze_min_age</>, <literal>toast.autovacuum_freeze_min_age</literal> (<type>integer</>)</term>
<listitem>
<para>
- Custom <xref linkend="guc-vacuum-freeze-min-age"> parameter. Note that
- autovacuum will ignore attempts to set a per-table
- <literal>autovacuum_freeze_min_age</> larger than half the system-wide
- <xref linkend="guc-autovacuum-freeze-max-age"> setting.
+ Per-table value for <xref linkend="guc-vacuum-freeze-min-age">
+ parameter. Note that autovacuum will ignore
+ per-table <literal>autovacuum_freeze_min_age</> parameters that are
+ larger than half the
+ system-wide <xref linkend="guc-autovacuum-freeze-max-age"> setting.
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_freeze_max_age</>, <literal>toast.autovacuum_freeze_max_age</literal> (<type>integer</>)</term>
<listitem>
<para>
- Custom <xref linkend="guc-autovacuum-freeze-max-age"> parameter. Note that
- autovacuum will ignore attempts to set a per-table
- <literal>autovacuum_freeze_max_age</> larger than the system-wide setting
- (it can only be set smaller).
+ Per-table value for <xref linkend="guc-autovacuum-freeze-max-age">
+ parameter. Note that autovacuum will ignore
+ per-table <literal>autovacuum_freeze_max_age</> parameters that are
+ larger than the system-wide setting (it can only be set smaller).
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_freeze_table_age</literal>, <literal>toast.autovacuum_freeze_table_age</literal> (<type>integer</type>)</term>
<listitem>
<para>
- Custom <xref linkend="guc-vacuum-freeze-table-age"> parameter.
+ Per-table value for <xref linkend="guc-vacuum-freeze-table-age">
+ parameter.
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_multixact_freeze_min_age</literal>, <literal>toast.autovacuum_multixact_freeze_min_age</literal> (<type>integer</type>)</term>
<listitem>
<para>
- Custom <xref linkend="guc-vacuum-multixact-freeze-min-age"> parameter.
- Note that autovacuum will ignore attempts to set a per-table
- <literal>autovacuum_multixact_freeze_min_age</> larger than half the
+ Per-table value for <xref linkend="guc-vacuum-multixact-freeze-min-age">
+ parameter. Note that autovacuum will ignore
+ per-table <literal>autovacuum_multixact_freeze_min_age</> parameters
+ that are larger than half the
system-wide <xref linkend="guc-autovacuum-multixact-freeze-max-age">
setting.
</para>
<term><literal>autovacuum_multixact_freeze_max_age</literal>, <literal>toast.autovacuum_multixact_freeze_max_age</literal> (<type>integer</type>)</term>
<listitem>
<para>
- Custom <xref linkend="guc-autovacuum-multixact-freeze-max-age"> parameter. Note
- that autovacuum will ignore attempts to set a per-table
- <literal>autovacuum_multixact_freeze_max_age</> larger than the
- system-wide setting (it can only be set smaller).
+ Per-table value
+ for <xref linkend="guc-autovacuum-multixact-freeze-max-age"> parameter.
+ Note that autovacuum will ignore
+ per-table <literal>autovacuum_multixact_freeze_max_age</> parameters
+ that are larger than the system-wide setting (it can only be set
+ smaller).
</para>
</listitem>
</varlistentry>
<term><literal>autovacuum_multixact_freeze_table_age</literal>, <literal>toast.autovacuum_multixact_freeze_table_age</literal> (<type>integer</type>)</term>
<listitem>
<para>
- Custom <xref linkend="guc-vacuum-multixact-freeze-table-age"> parameter.
+ Per-table value
+ for <xref linkend="guc-vacuum-multixact-freeze-table-age"> parameter.
</para>
</listitem>
</varlistentry>
<term><literal>log_autovacuum_min_duration</literal>, <literal>toast.log_autovacuum_min_duration</literal> (<type>integer</type>)</term>
<listitem>
<para>
- Custom <xref linkend="guc-log-autovacuum-min-duration"> parameter.
+ Per-table value for <xref linkend="guc-log-autovacuum-min-duration">
+ parameter.
</para>
</listitem>
</varlistentry>
<term><literal>user_catalog_table</literal> (<type>boolean</type>)</term>
<listitem>
<para>
- Declare a table as an additional catalog table, e.g. for the purpose of
+ Declare the table as an additional catalog table for purposes of
logical replication. See
<xref linkend="logicaldecoding-capabilities"> for details.
This parameter cannot be set for TOAST tables.
projects / users / heikki / postgres.git / commitdiff