add DropAllIndexes() method (#25)

Create a new method to drop all the indexes of a collection
in a single call

session.go

@@ -1499,6 +1499,29 @@ func (c *Collection) DropIndexName(name string) error {
 	return nil
 }
 
+// DropAllIndexes drops all the indexes from the c collection
+func (c *Collection) DropAllIndexes() error {
+	session := c.Database.Session
+	session.ResetIndexCache()
+
+	session = session.Clone()
+	defer session.Close()
+
+	db := c.Database.With(session)
+	result := struct {
+		ErrMsg string
+		Ok     bool
+	}{}
+	err := db.Run(bson.D{{"dropIndexes", c.Name}, {"index", "*"}}, &result)
+	if err != nil {
+		return err
+	}
+	if !result.Ok {
+		return errors.New(result.ErrMsg)
+	}
+	return nil
+}
+
 // nonEventual returns a clone of session and ensures it is not Eventual.
 // This guarantees that the server that is used for queries may be reused
 // afterwards when a cursor is received.
@@ -1512,19 +1535,6 @@ func (session *Session) nonEventual() *Session {
 
 // Indexes returns a list of all indexes for the collection.
 //
-// For example, this snippet would drop all available indexes:
-//
-//   indexes, err := collection.Indexes()
-//   if err != nil {
-//       return err
-//   }
-//   for _, index := range indexes {
-//       err = collection.DropIndex(index.Key...)
-//       if err != nil {
-//           return err
-//       }
-//   }
-//
 // See the EnsureIndex method for more details on indexes.
 func (c *Collection) Indexes() (indexes []Index, err error) {
 	cloned := c.Database.Session.nonEventual()

session_test.go

@@ -3478,6 +3478,31 @@ func (s *S) TestEnsureIndexDropIndexName(c *C) {
 	c.Assert(err, ErrorMatches, "index not found.*")
 }
 
+func (s *S) TestEnsureIndexDropAllIndexes(c *C) {
+	session, err := mgo.Dial("localhost:40001")
+	c.Assert(err, IsNil)
+	defer session.Close()
+
+	coll := session.DB("mydb").C("mycoll")
+
+	err = coll.EnsureIndexKey("a")
+	c.Assert(err, IsNil)
+
+	err = coll.EnsureIndexKey("b")
+	c.Assert(err, IsNil)
+
+	err = coll.DropAllIndexes()
+	c.Assert(err, IsNil)
+
+	sysidx := session.DB("mydb").C("system.indexes")
+
+	err = sysidx.Find(M{"name": "a_1"}).One(nil)
+	c.Assert(err, Equals, mgo.ErrNotFound)
+
+	err = sysidx.Find(M{"name": "b_1"}).One(nil)
+	c.Assert(err, Equals, mgo.ErrNotFound)
+}
+
 func (s *S) TestEnsureIndexCaching(c *C) {
 	session, err := mgo.Dial("localhost:40001")
 	c.Assert(err, IsNil)