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@ -1,5 +1,5 @@ |
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<!-- |
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$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.272 2004/08/05 23:32:10 tgl Exp $ |
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$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.273 2004/08/06 04:15:07 momjian Exp $ |
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--> |
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<Chapter Id="runtime"> |
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@ -1074,7 +1074,7 @@ SET ENABLE_SEQSCAN TO OFF; |
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cost reaches a limit (specified by |
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<varname>vacuum_cost_limit</varname>), the process performing |
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the operation will sleep for a while (specified by |
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<varname>vacuum_cost_naptime</varname>). Then it will reset the |
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<varname>vacuum_cost_delay</varname>). Then it will reset the |
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counter and continue execution. |
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</para> |
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@ -1092,7 +1092,7 @@ SET ENABLE_SEQSCAN TO OFF; |
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<para> |
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This feature is disabled by default. To enable it, set the |
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<varname>vacuum_cost_naptime</varname> variable to a nonzero |
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<varname>vacuum_cost_delay</varname> variable to a nonzero |
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value. |
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</para> |
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@ -1143,8 +1143,8 @@ SET ENABLE_SEQSCAN TO OFF; |
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</listitem> |
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</varlistentry> |
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<varlistentry id="guc-vacuum-cost-naptime" xreflabel="vacuum_cost_naptime"> |
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<term><varname>vacuum_cost_naptime</varname> (<type>integer</type>)</term> |
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<varlistentry id="guc-vacuum-cost-delay" xreflabel="vacuum_cost_delay"> |
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<term><varname>vacuum_cost_delay</varname> (<type>integer</type>)</term> |
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<listitem> |
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<para> |
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The length of time, in milliseconds, that the process will nap |
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@ -1153,7 +1153,7 @@ SET ENABLE_SEQSCAN TO OFF; |
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delay feature. Positive values enable cost-based vacuuming. |
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Note however that on many systems, the effective resolution |
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of sleep delays is 10 milliseconds; setting |
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<varname>vacuum_cost_naptime</varname> to a value that is |
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<varname>vacuum_cost_delay</varname> to a value that is |
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not a multiple of 10 may have the same results as setting it |
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to the next higher multiple of 10. |
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</para> |
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@ -1168,10 +1168,10 @@ SET ENABLE_SEQSCAN TO OFF; |
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delays do not occur during such operations. Therefore it is |
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possible that the cost accumulates far higher than the specified |
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limit. To avoid uselessly long delays in such cases, the actual |
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naptime is calculated as <varname>vacuum_cost_naptime</varname> * |
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delay is calculated as <varname>vacuum_cost_delay</varname> * |
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<varname>accumulated_balance</varname> / |
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<varname>vacuum_cost_limit</varname> with a maximum of |
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<varname>vacuum_cost_naptime</varname> * 4. |
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<varname>vacuum_cost_delay</varname> * 4. |
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</para> |
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</note> |
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