Document use of partial indexes for partial unique constraints

Report by Tomáš Greif

Backpatch through 9.4

diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 8ace8bd3a2537849cdaac52b620baa8ed97a9095..ceb83798c899d1daaae27e55a090bd2ac7c06278 100644 (file)
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -546,7 +546,9 @@ CREATE TABLE products (
 
    
     Adding a unique constraint will automatically create a unique btree
-    index on the column or group of columns used in the constraint.
+    index on the column or group of columns used in the constraint. 
+    A uniqueness constraint on only some rows can be enforced by creating
+    a partial index.