A bit more editing for collation documentation.

diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index b4c4b5e23ef2a82354b88ce2f96b207a3723e13e..48223943000a43f233679b0afa201871c1fd5f09 100644 (file)
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1257,6 +1257,12 @@ SELECT 3 OPERATOR(pg_catalog.+) 4;
      
     
 
+    
+     
+      A collation expression
+     
+    
+
     
      
       A scalar subquery
@@ -1898,8 +1904,8 @@ CAST ( expression AS type
    
   
 
-  clause">
-   C<span class="marked">OLLATE Clause</span>
+  exprs">
+   C<span class="marked">ollation Expressions</span>
 
    
     COLLATE
@@ -1925,7 +1931,7 @@ CAST ( expression AS type
    
 
    
-    The two typical uses of the COLLATE clause are
+    The two common uses of the COLLATE clause are
     overriding the sort order in an ORDER BY clause, for
     example:
 
@@ -1934,15 +1940,28 @@ SELECT a, b, c FROM tbl WHERE ... ORDER BY a COLLATE "C";
     and overriding the collation of a function or operator call that
     has locale-sensitive results, for example:
 
-SELECT * FROM tbl WHERE a > 'foo' COLLATE "C";
+SELECT * FROM tbl WHERE a > 'foo' COLLATE "C";
+
+    Note that in the latter case the COLLATE clause is
+    attached to an input argument of the operator we wish to affect.
+    It doesn't matter which argument of the operator or function call the
+    COLLATE clause is attached to, because the collation that is
+    applied by the operator or function is derived by considering all
+    arguments, and an explicit COLLATE clause will override the
+    collations of all other arguments.  (Attaching non-matching
+    COLLATE clauses to more than one argument, however, is an
+    error.  For more details see .)
+    Thus, this gives the same result as the previous example:
+
+SELECT * FROM tbl WHERE a COLLATE "C" > 'foo';
+
+    But this is an error:
+
+SELECT * FROM tbl WHERE (a > 'foo') COLLATE "C";
 
-    In the latter case it doesn't matter which argument of the
-    operator of function call the COLLATE clause is
-    attached to, because the collation that is applied by the operator
-    or function is derived from all arguments, and
-    the COLLATE clause will override the collations of all
-    other arguments.  Attaching nonmatching COLLATE
-    clauses to more than one argument, however, is an error.
+    because it attempts to apply a collation to the result of the
+    > operator, which is of the non-collatable data type
+    boolean.