Fix inaccurate description of deferrable unique constraints, per Dean Rasheed.

diff --git a/doc/src/sgml/release-9.0.sgml b/doc/src/sgml/release-9.0.sgml
index d9467fd89f7680c7fdcab2f80952789c0d91e20d..b7ce612cac7ba87cff283c8072b3b924376b67d0 100644 (file)
--- a/doc/src/sgml/release-9.0.sgml
+++ b/doc/src/sgml/release-9.0.sgml
@@ -1,4 +1,4 @@
-
+
 
  
   Release 9.0
@@ -91,7 +91,8 @@
     
      
       Deferrable
-      unique constraints, now permit mass updates to unique keys.
+      unique constraints. Mass updates to unique keys are now possible
+      without trickery.
      
     
 
@@ -1122,10 +1123,13 @@
       
 
       
-       This allows UPDATE tab SET col = col + 1 to work on
-       columns that have a unique indexes or are marked as primary key,
-       but DEFERRABLE INITIALLY DEFERRED must be used to mark
-       the constraint as deferred.
+       This allows UPDATE tab SET col = col + 1 to work reliably
+       on columns that have unique indexes or are marked as primary keys.
+       If the constraint is specified as DEFERRABLE it will be
+       checked at the end of the statement, rather than after each row is
+       updated. The constraint check may also be deferred until the end of the
+       current transaction, allowing updates to be spread over multiple SQL
+       commands.