Add documentaiotn mention that constraint names can be sentences that

can convey information to clients on constraint violation.

diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index adfcd13ff0da3028bcfc941d3953c7a619ff7df1..2c5e14caf2438ad097560684e5c6d1ee8299f426 100644 (file)
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -1,5 +1,5 @@
 
 
@@ -293,7 +293,10 @@ and table_constraint is:
     CONSTRAINT constraint_name
     
      
-      An optional name for a column or table constraint.  If not specified,
+      An optional name for a column or table constraint.  If the
+      constraint is violated, the constraint name is present in error messages,
+      so constraint names like "col must be positive" can be used to communicate
+      helpful constraint information to client applications.  If not specified,
       the system generates a name.