Add documentation for pointer to pointer null mapping

CHANGELOG.md

@@ -1,5 +1,6 @@
 # Master
 
+* Add null mapping to pointer to pointer (Jonathan Rudenberg)
 * Add JSON and JSONB type support (Joseph Glanville)
 
 # 2.6.0 (September 3, 2015)

README.md

@@ -22,6 +22,7 @@ Pgx supports many additional features beyond what is available through database/
 * JSON and JSONB support
 * Maps inet and cidr PostgreSQL types to net.IPNet
 * Large object support
+* Null mapping to Null* struct or pointer to pointer.
 
 ## Performance
 

doc.go

@@ -121,8 +121,16 @@ notification.
 
 Null Mapping
 
-pgx includes Null* types in a similar fashion to database/sql that implement the
+pgx can map nulls in two ways. The first is Null* types that have a data field
-necessary interfaces to be encoded and scanned.
+and a valid field. They work in a similar fashion to database/sql. The second
+is to use a pointer to a pointer.
+
+    var foo pgx.NullString
+    var bar *string
+    err := conn.QueryRow("select foo, bar from widgets where id=$1", 42).Scan(&a, &b)
+    if err != nil {
+        return err
+    }
 
 Array Mapping