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Diffstat (limited to 'doc/src/sgml/monitoring.sgml')
| -rw-r--r-- | doc/src/sgml/monitoring.sgml | 28 |
1 files changed, 6 insertions, 22 deletions
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index fd9bdd88472..16646f560e8 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -4234,32 +4234,16 @@ description | Waiting for a newly initialized WAL file to reach durable storage <note> <para> - Index scans may sometimes perform multiple index searches per execution. - Each index search increments <structname>pg_stat_all_indexes</structname>.<structfield>idx_scan</structfield>, + Queries that use certain <acronym>SQL</acronym> constructs to search for + rows matching any value out of a list or array of multiple scalar values + (see <xref linkend="functions-comparisons"/>) perform multiple + <quote>primitive</quote> index scans (up to one primitive scan per scalar + value) during query execution. Each internal primitive index scan + increments <structname>pg_stat_all_indexes</structname>.<structfield>idx_scan</structfield>, so it's possible for the count of index scans to significantly exceed the total number of index scan executor node executions. </para> - <para> - This can happen with queries that use certain <acronym>SQL</acronym> - constructs to search for rows matching any value out of a list or array of - multiple scalar values (see <xref linkend="functions-comparisons"/>). It - can also happen to queries with a - <literal><replaceable>column_name</replaceable> = - <replaceable>value1</replaceable> OR - <replaceable>column_name</replaceable> = - <replaceable>value2</replaceable> ...</literal> construct, though only - when the optimizer transforms the construct into an equivalent - multi-valued array representation. - </para> </note> - <tip> - <para> - <command>EXPLAIN ANALYZE</command> outputs the total number of index - searches performed by each index scan node. See - <xref linkend="using-explain-analyze"/> for an example demonstrating how - this works. - </para> - </tip> </sect2> |