add support for unique index creation

lib/mongo/collection.rb

@@ -117,8 +117,10 @@ module XGen
         # should be either a single field name or a Array of [field name,
         # direction] pairs. Directions should be specified as
         # XGen::Mongo::ASCENDING or XGen::Mongo::DESCENDING.
-        def create_index(field_or_spec)
-          @db.create_index(@name, field_or_spec)
+        # +unique+ is an optional boolean indicating whether this index
+        # should enforce a uniqueness constraint.
+        def create_index(field_or_spec, unique=false)
+          @db.create_index(@name, field_or_spec, unique)
         end
 
         # Drop index +name+.

lib/mongo/db.rb

@@ -430,8 +430,9 @@ module XGen
         # should be either a single field name or a Array of [field name,
         # direction] pairs. Directions should be specified as
         # XGen::Mongo::ASCENDING or XGen::Mongo::DESCENDING. Normally called
-        # by Collection#create_index.
-        def create_index(collection_name, field_or_spec)
+        # by Collection#create_index. If +unique+ is true the index will
+        # enforce a uniqueness constraint.
+        def create_index(collection_name, field_or_spec, unique=false)
           field_h = OrderedHash.new
           if field_or_spec.is_a? String
             field_h[field_or_spec] = 1
@@ -442,7 +443,8 @@ module XGen
           sel = {
             :name => name,
             :ns => full_coll_name(collection_name),
-            :key => field_h
+            :key => field_h,
+            :unique => unique
           }
           @semaphore.synchronize {
             send_to_db(InsertMessage.new(@name, SYSTEM_INDEX_COLLECTION, sel))

tests/test_db_api.rb

@@ -309,6 +309,28 @@ class DBAPITest < Test::Unit::TestCase
     @@db.drop_index(@@coll.name, name)
   end
 
+  def test_unique_index
+    @@db.drop_collection("blah")
+    test = @@db.collection("blah")
+    test.create_index("hello")
+
+    test.insert("hello" => "world")
+    test.insert("hello" => "mike")
+    test.insert("hello" => "world")
+    assert !@@db.error?
+
+    @@db.drop_collection("blah")
+    test = @@db.collection("blah")
+    test.create_index("hello", unique=true)
+
+    test.insert("hello" => "world")
+    test.insert("hello" => "mike")
+    test.insert("hello" => "world")
+    assert @@db.error?
+
+    @@db.drop_collection("blah")
+  end
+
   def test_array
     @@coll << {'b' => [1, 2, 3]}
     rows = @@coll.find({}, {:fields => ['b']}).to_a