Document partial indexes for IS NULL lookups.

diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml
index 34e12c6a5d23cb6508a410869863bb327b80b0ea..43583df54d51354fdea9a1ae7886df11ef8e916f 100644 (file)
--- a/doc/src/sgml/ref/create_index.sgml
+++ b/doc/src/sgml/ref/create_index.sgml
@@ -1,5 +1,5 @@
 
 
@@ -77,11 +77,9 @@ CREATE [ UNIQUE ] INDEX name ON 
   
 
   
-   NULL values are not indexed by default.  The best way
-   to index NULL values is to create a partial index using
-   an IS NULL comparison.  IS NULL is more
-   of a function call than a value comparison, and this is why a partial
-   index works.
+   Indexes can not be used with IS NULL clauses by default.
+   The best way to use indexes in such cases is to create a partial index 
+   using an IS NULL comparison.