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Performance tuning advice for SSI.

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Kevin Grittner, with additional wordsmithing by me.
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Robert Haas 2011-06-21 21:54:36 -04:00
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doc/src/sgml/mvcc.sgml
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@ -658,6 +658,26 @@ ERROR: could not serialize access due to read/write dependencies among transact
protections automatically provided by Serializable transactions. protections automatically provided by Serializable transactions.
</para> </para>
</listitem> </listitem>
<listitem>
<para>
When the system is forced to combine multiple page-level predicate
locks into a single relation-level predicate lock because the predicate
lock table is short of memory, an increase in the rate of serialization
failures may occur. You can avoid this by increasing
<xref linkend="guc-max-pred-locks-per-transaction">.
</para>
</listitem>
<listitem>
<para>
A sequential scan will always necessitate a relation-level predicate
lock. This can result in an increased rate of serialization failures.
It may be helpful to encourage the use of index scans by reducing
<xref linkend="guc-random-page-cost"> and/or increasing
<xref linkend="guc-cpu-tuple-cost">. Be sure to weigh any decrease
in transaction rollbacks and restarts against any overall change in
query execution time.
</para>
</listitem>
</itemizedlist> </itemizedlist>
</para> </para>