diff options
| -rw-r--r-- | doc/src/sgml/maintenance.sgml | 29 | ||||
| -rw-r--r-- | doc/src/sgml/ref/analyze.sgml | 32 |
2 files changed, 58 insertions, 3 deletions
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml index de71cb456a5..1a4585ef90a 100644 --- a/doc/src/sgml/maintenance.sgml +++ b/doc/src/sgml/maintenance.sgml @@ -291,6 +291,15 @@ </para> <para> + Tuples changed in partitions and inheritance children do not trigger + analyze on the parent table. If the parent table is empty or rarely + changed, it may never be processed by autovacuum, and the statistics for + the inheritance tree as a whole won't be collected. It is necessary to + run <command>ANALYZE</command> on the parent table manually in order to + keep the statistics up to date. + </para> + + <para> As with vacuuming for space recovery, frequent updates of statistics are more useful for heavily-updated tables than for seldom-updated ones. But even for a heavily-updated table, there might be no need for @@ -346,6 +355,19 @@ <command>ANALYZE</command> commands on those tables on a suitable schedule. </para> </tip> + + <tip> + <para> + The autovacuum daemon does not issue <command>ANALYZE</command> commands + for partitioned tables. Inheritance parents will only be analyzed if the + parent itself is changed - changes to child tables do not trigger + autoanalyze on the parent table. If your queries require statistics on + parent tables for proper planning, it is necessary to periodically run + a manual <command>ANALYZE</command> on those tables to keep the statistics + up to date. + </para> + </tip> + </sect2> <sect2 id="vacuum-for-visibility-map"> @@ -799,6 +821,13 @@ analyze threshold = analyze base threshold + analyze scale factor * number of tu </para> <para> + Partitioned tables are not processed by autovacuum. Statistics + should be collected by running a manual <command>ANALYZE</command> when it is + first populated, and again whenever the distribution of data in its + partitions changes significantly. + </para> + + <para> Temporary tables cannot be accessed by autovacuum. Therefore, appropriate vacuum and analyze operations should be performed via session SQL commands. diff --git a/doc/src/sgml/ref/analyze.sgml b/doc/src/sgml/ref/analyze.sgml index 5ac3ba83219..ae04a684cbd 100644 --- a/doc/src/sgml/ref/analyze.sgml +++ b/doc/src/sgml/ref/analyze.sgml @@ -264,9 +264,35 @@ ANALYZE [ VERBOSE ] [ <replaceable class="parameter">table_and_columns</replacea </para> <para> - If any of the child tables are foreign tables whose foreign data wrappers - do not support <command>ANALYZE</command>, those child tables are ignored while - gathering inheritance statistics. + For partitioned tables, <command>ANALYZE</command> gathers statistics by + sampling rows from all partitions; in addition, it will recurse into each + partition and update its statistics. Each leaf partition is analyzed only + once, even with multi-level partitioning. No statistics are collected for + only the parent table (without data from its partitions), because with + partitioning it's guaranteed to be empty. + </para> + + <para> + By constrast, if the table being analyzed has inheritance children, + <command>ANALYZE</command> gathers two sets of statistics: one on the rows + of the parent table only, and a second including rows of both the parent + table and all of its children. This second set of statistics is needed when + planning queries that process the inheritance tree as a whole. The child + tables themselves are not individually analyzed in this case. + </para> + + <para> + The autovacuum daemon does not process partitioned tables, nor does it + process inheritance parents if only the children are ever modified. + It is usually necessary to periodically run a manual + <command>ANALYZE</command> to keep the statistics of the table hierarchy + up to date. + </para> + + <para> + If any child tables or partitions are foreign tables whose foreign + data wrappers do not support <command>ANALYZE</command>, those tables are + ignored while gathering inheritance statistics. </para> <para> |