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doc: simplify docs about analyze and inheritance/partitions 

Discussion: https://postgr.es/m/YxAqYijOsLzgLQgy@momjian.us

Backpatch-through: 10
This commit is contained in:
Bruce Momjian 2022-09-02 23:32:18 -04:00
parent b9dce0d8ae
commit e5a5b97052
1 changed files with 7 additions and 15 deletions
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22
doc/src/sgml/ref/analyze.sgml
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@ -200,12 +200,13 @@ ANALYZE [ VERBOSE ] [ <replaceable class="PARAMETER">table_name</replaceable> [
</para>
<para>
If the table being analyzed has one or more children,
<command>ANALYZE</command> will gather statistics twice: once on the
rows of the parent table only, and a second time on the rows of the
parent table with all of its children. This second set of statistics
is needed when planning queries that traverse the entire inheritance
tree. The autovacuum daemon, however, will only consider inserts or
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.
The autovacuum daemon, however, will only consider inserts or
updates on the parent table itself when deciding whether to trigger an
automatic analyze for that table. If that table is rarely inserted into
or updated, the inheritance statistics will not be up to date unless you
@ -221,15 +222,6 @@ ANALYZE [ VERBOSE ] [ <replaceable class="PARAMETER">table_name</replaceable> [
partitioning it's guaranteed to be empty.
</para>
<para>
By contrast, 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.