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Diffstat (limited to 'doc/src/sgml/maintenance.sgml')
| -rw-r--r-- | doc/src/sgml/maintenance.sgml | 76 |
1 files changed, 26 insertions, 50 deletions
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml index ad9c38da55b..2b6f53bcffa 100644 --- a/doc/src/sgml/maintenance.sgml +++ b/doc/src/sgml/maintenance.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.89 2009/01/16 13:27:23 heikki Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.90 2009/02/09 20:57:59 alvherre Exp $ --> <chapter id="maintenance"> <title>Routine Database Maintenance Tasks</title> @@ -573,7 +573,9 @@ HINT: Stop the postmaster and use a standalone backend to VACUUM in "mydb". <para> Tables whose <structfield>relfrozenxid</> value is more than <varname>autovacuum_freeze_max_age</> transactions old are always - vacuumed. Otherwise, if the number of tuples obsoleted since the last + vacuumed (this also applies to those tables whose freeze max age has + been modified via storage parameters; see below). Otherwise, if the + number of tuples obsoleted since the last <command>VACUUM</command> exceeds the <quote>vacuum threshold</quote>, the table is vacuumed. The vacuum threshold is defined as: <programlisting> @@ -604,66 +606,40 @@ analyze threshold = analyze base threshold + analyze scale factor * number of tu <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 by making entries in the system catalog - <link - linkend="catalog-pg-autovacuum"><structname>pg_autovacuum</></link>. - If a <structname>pg_autovacuum</structname> row exists for a particular - table, the settings it specifies are applied; otherwise the global - settings are used. See <xref linkend="runtime-config-autovacuum"> for + on a table-by-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 five - more parameters that can be set for each table in - <structname>pg_autovacuum</structname>. - The first, <structname>pg_autovacuum</>.<structfield>enabled</>, + 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. - The next two parameters, the vacuum cost delay - (<structname>pg_autovacuum</structname>.<structfield>vac_cost_delay</structfield>) - and the vacuum cost limit - (<structname>pg_autovacuum</structname>.<structfield>vac_cost_limit</structfield>), - are used to set table-specific values for the - <xref linkend="runtime-config-resource-vacuum-cost" endterm="runtime-config-resource-vacuum-cost-title"> + Another two parameters, + <literal>autovacuum_vacuum_cost_delay</literal> and + <literal>autovacuum_vacuum_cost_limit</literal>, are used to set + table-specific values for the + <xref linkend="runtime-config-resource-vacuum-cost" + endterm="runtime-config-resource-vacuum-cost-title"> feature. - The last two parameters, - (<structname>pg_autovacuum</structname>.<structfield>freeze_min_age</structfield>) - and - (<structname>pg_autovacuum</structname>.<structfield>freeze_max_age</structfield>), - are used to set table-specific values for - <xref linkend="guc-vacuum-freeze-min-age"> and - <xref linkend="guc-autovacuum-freeze-max-age"> respectively. + <literal>autovacuum_freeze_min_age</literal>, + <literal>autovacuum_freeze_max_age</literal> and + <literal>autovacuum_freeze_table_age</literal> 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> - If any of the values in <structname>pg_autovacuum</structname> - are set to a negative number, or if a row is not present at all in - <structname>pg_autovacuum</structname> for any particular table, the - corresponding values from <filename>postgresql.conf</filename> are used. - </para> - - <para> - There is not currently any support for making - <structname>pg_autovacuum</structname> entries, except by doing - manual <command>INSERT</>s into the catalog. This feature will be - improved in future releases, and it is likely that the catalog - definition will change. - </para> - - <caution> - <para> - The contents of the <structname>pg_autovacuum</structname> system - catalog are currently not saved in database dumps created by the - tools <application>pg_dump</> and <application>pg_dumpall</>. If - you want to preserve them across a dump/reload cycle, make sure - you dump the catalog manually. - </para> - </caution> - - <para> When multiple workers are running, the cost limit is <quote>balanced</quote> among all the running workers, so that the total impact on the system is the same, regardless of the number |