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Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/perform.sgml | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml index c32e95a1542..b50357c3b4e 100644 --- a/doc/src/sgml/perform.sgml +++ b/doc/src/sgml/perform.sgml @@ -894,6 +894,18 @@ EXPLAIN ANALYZE SELECT * FROM tenk1 WHERE unique1 < 100 AND unique2 > 9000 BitmapAnd and BitmapOr nodes always report their actual row counts as zero, due to implementation limitations. </para> + + <para> + Generally, the <command>EXPLAIN</command> output will display details for + every plan node which was generated by the query planner. However, there + are cases where the executor is able to determine that certain nodes are + not required; currently, the only node type to support this is the + <literal>Append</literal> node. This node type has the ability to discard + subnodes which it is able to determine won't contain any records required + by the query. It is possible to determine that nodes have been removed in + this way by the presence of a "Subplans Removed" property in the + <command>EXPLAIN</command> output. + </para> </sect2> </sect1> |