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postgresql8.3-docs-8.3.6-2mdv2008.1.x86_64.rpm

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><H1
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><A
NAME="CATALOG-PG-AUTOVACUUM"
>44.10. <TT
CLASS="STRUCTNAME"
>pg_autovacuum</TT
></A
></H1
><A
NAME="AEN68839"
></A
><A
NAME="AEN68841"
></A
><P
>   The catalog <TT
CLASS="STRUCTNAME"
>pg_autovacuum</TT
> stores optional
   per-relation configuration parameters for the autovacuum daemon.
   If there is an entry here for a particular relation, the given
   parameters will be used for autovacuuming that table.  If no entry
   is present, the system-wide defaults will be used. For more information
   about the autovacuum daemon, see <A
HREF="routine-vacuuming.html#AUTOVACUUM"
>Section 23.1.4</A
>.
  </P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>    It is likely that <TT
CLASS="STRUCTNAME"
>pg_autovacuum</TT
> will disappear
    in a future release, with the information instead being kept in
    <TT
CLASS="STRUCTNAME"
>pg_class</TT
>.<TT
CLASS="STRUCTFIELD"
>reloptions</TT
> entries.
   </P
></BLOCKQUOTE
></DIV
><DIV
CLASS="TABLE"
><A
NAME="AEN68852"
></A
><P
><B
>Table 44-10. <TT
CLASS="STRUCTNAME"
>pg_autovacuum</TT
> Columns</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Type</TH
><TH
>References</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>vacrelid</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-class.html"
><TT
CLASS="STRUCTNAME"
>pg_class</TT
></A
>.oid</TT
></TD
><TD
>The table this entry is for</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>enabled</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>If false, this table will not be autovacuumed, except
       to prevent transaction ID wraparound</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>vac_base_thresh</TT
></TD
><TD
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
>&nbsp;</TD
><TD
>Minimum number of modified tuples before vacuum</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>vac_scale_factor</TT
></TD
><TD
><TT
CLASS="TYPE"
>float4</TT
></TD
><TD
>&nbsp;</TD
><TD
>Multiplier for <TT
CLASS="STRUCTFIELD"
>reltuples</TT
> to add to
       <TT
CLASS="STRUCTFIELD"
>vac_base_thresh</TT
></TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>anl_base_thresh</TT
></TD
><TD
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
>&nbsp;</TD
><TD
>Minimum number of modified tuples before analyze</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>anl_scale_factor</TT
></TD
><TD
><TT
CLASS="TYPE"
>float4</TT
></TD
><TD
>&nbsp;</TD
><TD
>Multiplier for <TT
CLASS="STRUCTFIELD"
>reltuples</TT
> to add to
       <TT
CLASS="STRUCTFIELD"
>anl_base_thresh</TT
></TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>vac_cost_delay</TT
></TD
><TD
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
>&nbsp;</TD
><TD
>Custom <TT
CLASS="VARNAME"
>vacuum_cost_delay</TT
> parameter</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>vac_cost_limit</TT
></TD
><TD
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
>&nbsp;</TD
><TD
>Custom <TT
CLASS="VARNAME"
>vacuum_cost_limit</TT
> parameter</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>freeze_min_age</TT
></TD
><TD
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
>&nbsp;</TD
><TD
>Custom <TT
CLASS="VARNAME"
>vacuum_freeze_min_age</TT
> parameter</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>freeze_max_age</TT
></TD
><TD
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
>&nbsp;</TD
><TD
>Custom <TT
CLASS="VARNAME"
>autovacuum_freeze_max_age</TT
> parameter</TD
></TR
></TBODY
></TABLE
></DIV
><P
>   The autovacuum daemon will initiate a <TT
CLASS="COMMAND"
>VACUUM</TT
> operation
   on a particular table when the number of updated or deleted tuples
   exceeds <TT
CLASS="STRUCTFIELD"
>vac_base_thresh</TT
> plus
   <TT
CLASS="STRUCTFIELD"
>vac_scale_factor</TT
> times the number of
   live tuples currently estimated to be in the relation.
   Similarly, it will initiate an <TT
CLASS="COMMAND"
>ANALYZE</TT
> operation
   when the number of inserted, updated or deleted tuples
   exceeds <TT
CLASS="STRUCTFIELD"
>anl_base_thresh</TT
> plus
   <TT
CLASS="STRUCTFIELD"
>anl_scale_factor</TT
> times the number of
   live tuples currently estimated to be in the relation.
  </P
><P
>   Also, the autovacuum daemon will perform a <TT
CLASS="COMMAND"
>VACUUM</TT
> operation
   to prevent transaction ID wraparound if the table's
   <TT
CLASS="STRUCTNAME"
>pg_class</TT
>.<TT
CLASS="STRUCTFIELD"
>relfrozenxid</TT
> field attains an age
   of more than <TT
CLASS="STRUCTFIELD"
>freeze_max_age</TT
> transactions, whether the table
   has been changed or not, even if
   <TT
CLASS="STRUCTNAME"
>pg_autovacuum</TT
>.<TT
CLASS="STRUCTFIELD"
>enabled</TT
> is set to
   <TT
CLASS="LITERAL"
>false</TT
> for it.  The system will launch autovacuum to perform
   such <TT
CLASS="COMMAND"
>VACUUM</TT
>s even if autovacuum is otherwise disabled.
   See <A
HREF="routine-vacuuming.html#VACUUM-FOR-WRAPAROUND"
>Section 23.1.3</A
> for more about wraparound
   prevention.
  </P
><P
>   Any of the numerical fields can contain <TT
CLASS="LITERAL"
>-1</TT
> (or indeed
   any negative value) to indicate that the system-wide default should
   be used for this particular value.  Observe that the
   <TT
CLASS="STRUCTFIELD"
>vac_cost_delay</TT
> variable inherits its default value from the
   <A
HREF="runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-COST-DELAY"
>autovacuum_vacuum_cost_delay</A
> configuration parameter,
   or from <A
HREF="runtime-config-resource.html#GUC-VACUUM-COST-DELAY"
>vacuum_cost_delay</A
> if the former is set to a
   negative value.  The same applies to <TT
CLASS="STRUCTFIELD"
>vac_cost_limit</TT
>.
   Also, autovacuum will ignore attempts to set a per-table
   <TT
CLASS="STRUCTFIELD"
>freeze_max_age</TT
> larger than the system-wide setting (it can
   only be set smaller), and the <TT
CLASS="STRUCTFIELD"
>freeze_min_age</TT
> value will be
   limited to half the system-wide <A
HREF="runtime-config-autovacuum.html#GUC-AUTOVACUUM-FREEZE-MAX-AGE"
>autovacuum_freeze_max_age</A
> setting.  Note that while you
   can set <TT
CLASS="STRUCTFIELD"
>freeze_max_age</TT
> very small, or even zero, this
   is usually unwise since it will force frequent vacuuming.
  </P
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