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 0fcd9f87062c7eb7c90c5c105fa81644edb91873..c07f5a203dde0b2161b1912d260a44e398a2ce79 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.