Mention hash opclasses in 'System Dependencies on Operator Classes',

which previously only talked about btree opclasses.

diff --git a/doc/src/sgml/xindex.sgml b/doc/src/sgml/xindex.sgml
index 0e92b3c65522d77f20cdaba852ffcc6a60c523a0..68d3123ef853919b70122c37d1d063e8ceb6980b 100644 (file)
--- a/doc/src/sgml/xindex.sgml
+++ b/doc/src/sgml/xindex.sgml
@@ -1,4 +1,4 @@
-
+
 
 
  Interfacing Extensions To Indexes
@@ -893,6 +893,13 @@ ALTER OPERATOR FAMILY integer_ops USING btree ADD
      any assumption about the behavior of operators with particular names.
     
    
+
+  
+   Another important point is that an operator that
+   appears in a hash operator family is a candidate for hash joins,
+   hash aggregation, and related optimizations.  The hash operator family
+   is essential here since it identifies the hash function(s) to use.
+  
  
 
  
@@ -950,7 +957,7 @@ CREATE OPERATOR CLASS polygon_ops
    is used.  In GIN, the STORAGE type identifies the type of
    the key values, which normally is different from the type
    of the indexed column — for example, an operator class for
-   integer array columns might have keys that are just integers.  The
+   integer-array columns might have keys that are just integers.  The
    GIN extractValue and extractQuery support
    routines are responsible for extracting keys from indexed values.