diff --git a/reference/mongo/mongocollection/ensureindex.xml b/reference/mongo/mongocollection/ensureindex.xml
index edd23f368e..dba8d549b6 100644
--- a/reference/mongo/mongocollection/ensureindex.xml
+++ b/reference/mongo/mongocollection/ensureindex.xml
@@ -60,9 +60,11 @@
- A unique index cannot be created on a field if multiple existing documents do
- not contain the field. The field is effectively &null; for these documents
- and thus already non-unique.
+ A unique index cannot be created on a field if multiple existing
+ documents do not contain the field. The field is effectively &null;
+ for these documents and thus already non-unique. Sparse indexing may
+ be used to overcome this, since it will prevent documents without the
+ field from being indexed.
@@ -75,6 +77,32 @@
all but one duplicate value.
+
+
+ "sparse"
+
+
+ Create a sparse index, which only includes documents containing the
+ field. This option is only compatible with single-field indexes.
+
+
+
+
+ "expireAfterSeconds"
+
+
+ The value of this option should specify the number of seconds after
+ which a document should be considered expired and automatically
+ removed from the collection. This option is only compatible with
+ single-field indexes where the field will contain
+ MongoDate values.
+
+
+ This feature is available in MongoDB 2.2+. See
+ Expire Data from Collections by Setting TTL
+ for more information.
+
+ "background"