diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index afcfb89a28..71d06ce513 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -1382,8 +1382,8 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
- Indexes can be used via either simple index scans or bitmap>
- index scans. In a bitmap scan
+ Indexes can be used by simple index scans, bitmap> index scans,
+ and the optimizer. In a bitmap scan
the output of several indexes can be combined via AND or OR rules,
so it is difficult to associate individual heap row fetches
with specific indexes when a bitmap scan is used. Therefore, a bitmap
@@ -1393,6 +1393,9 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
pg_stat_all_tables>.idx_tup_fetch>
count for the table, but it does not affect
pg_stat_all_indexes>.idx_tup_fetch>.
+ The optimizer also accesses indexes to check for supplied constants
+ whose values are outside the recorded range of the optimizer statistics
+ because the optimizer statistics might be stale.