Have Update() and Remove() return ChangeInfo

session.go

@@ -3090,6 +3090,11 @@ func (c *Collection) Insert(docs ...interface{}) error {
 //     http://www.mongodb.org/display/DOCS/Atomic+Operations
 //
 func (c *Collection) Update(selector interface{}, update interface{}) error {
+	_, err := c.UpdateWithChangeInfo(selector, update)
+	return err
+}
+
+func (c *Collection) UpdateWithChangeInfo(selector interface{}, update interface{}) (info *ChangeInfo, err error) {
 	if selector == nil {
 		selector = bson.D{}
 	}
@@ -3099,10 +3104,13 @@ func (c *Collection) Update(selector interface{}, update interface{}) error {
 		Update:     update,
 	}
 	lerr, err := c.writeOp(&op, true)
-	if err == nil && lerr != nil && !lerr.UpdatedExisting {
-		return ErrNotFound
+	if err == nil && lerr != nil {
+		if !lerr.UpdatedExisting {
+			return info, ErrNotFound
+		}
+		info = &ChangeInfo{Updated: lerr.modified, Matched: lerr.N}
 	}
-	return err
+	return info, err
 }
 
 // UpdateId is a convenience helper equivalent to:
@@ -3247,14 +3255,22 @@ func (c *Collection) UpsertId(id interface{}, update interface{}) (info *ChangeI
 //     http://www.mongodb.org/display/DOCS/Removing
 //
 func (c *Collection) Remove(selector interface{}) error {
+	_, err := c.RemoveWithChangeInfo(selector)
+	return err
+}
+
+func (c *Collection) RemoveWithChangeInfo(selector interface{}) (info *ChangeInfo, err error) {
 	if selector == nil {
 		selector = bson.D{}
 	}
 	lerr, err := c.writeOp(&deleteOp{c.FullName, selector, 1, 1}, true)
-	if err == nil && lerr != nil && lerr.N == 0 {
-		return ErrNotFound
+	if err == nil && lerr != nil {
+		if lerr.N == 0 {
+			return info, ErrNotFound
+		}
+		info = &ChangeInfo{Removed: lerr.N, Matched: lerr.N}
 	}
-	return err
+	return info, err
 }
 
 // RemoveId is a convenience helper equivalent to:

session_test.go

@@ -683,6 +683,46 @@ func (s *S) TestUpdate(c *C) {
 	c.Assert(err, Equals, mgo.ErrNotFound)
 }
 
+func (s *S) TestUpdateWithChangeInfo(c *C) {
+	session, err := mgo.Dial("localhost:40001")
+	c.Assert(err, IsNil)
+	defer session.Close()
+
+	coll := session.DB("mydb").C("mycoll")
+
+	ns := []int{40, 41, 42, 43, 44, 45, 46}
+	for _, n := range ns {
+		err := coll.Insert(M{"k": n, "n": n})
+		c.Assert(err, IsNil)
+	}
+
+	// No changes is a no-op and shouldn't return an error.
+	info, err := coll.UpdateWithChangeInfo(M{"k": 42}, M{"$set": M{"n": 42}})
+	c.Assert(err, IsNil)
+	c.Assert(info.Matched, Equals, 1)
+	c.Assert(info.Updated, Equals, 0)
+	c.Assert(info.Removed, Equals, 0)
+	c.Assert(info.UpsertedId, IsNil)
+
+	info, err = coll.UpdateWithChangeInfo(M{"k": 42}, M{"$inc": M{"n": 1}})
+	c.Assert(err, IsNil)
+	c.Assert(info.Matched, Equals, 1)
+	c.Assert(info.Updated, Equals, 1)
+	c.Assert(info.Removed, Equals, 0)
+	c.Assert(info.UpsertedId, IsNil)
+
+	result := make(M)
+	err = coll.Find(M{"k": 42}).One(result)
+	c.Assert(err, IsNil)
+	c.Assert(result["n"], Equals, 43)
+
+	info, err = coll.UpdateWithChangeInfo(M{"k": 47}, M{"k": 47, "n": 47})
+	c.Assert(err, Equals, mgo.ErrNotFound)
+
+	err = coll.Find(M{"k": 47}).One(result)
+	c.Assert(err, Equals, mgo.ErrNotFound)
+}
+
 func (s *S) TestUpdateId(c *C) {
 	session, err := mgo.Dial("localhost:40001")
 	c.Assert(err, IsNil)
@@ -986,6 +1026,39 @@ func (s *S) TestRemove(c *C) {
 	c.Assert(result.N, Equals, 44)
 }
 
+func (s *S) TestRemoveWithChangeInfo(c *C) {
+	session, err := mgo.Dial("localhost:40001")
+	c.Assert(err, IsNil)
+	defer session.Close()
+
+	coll := session.DB("mydb").C("mycoll")
+
+	ns := []int{40, 41, 42, 43, 44, 45, 46}
+	for _, n := range ns {
+		err := coll.Insert(M{"n": n})
+		c.Assert(err, IsNil)
+	}
+
+	info, err := coll.RemoveWithChangeInfo(M{"n": M{"$gt": 42}})
+	c.Assert(err, IsNil)
+	c.Assert(info.Removed, Equals, 1)
+	c.Assert(info.Matched, Equals, 1)
+	c.Assert(info.Updated, Equals, 0)
+	c.Assert(info.UpsertedId, IsNil)
+
+	result := &struct{ N int }{}
+	err = coll.Find(M{"n": 42}).One(result)
+	c.Assert(err, IsNil)
+	c.Assert(result.N, Equals, 42)
+
+	err = coll.Find(M{"n": 43}).One(result)
+	c.Assert(err, Equals, mgo.ErrNotFound)
+
+	err = coll.Find(M{"n": 44}).One(result)
+	c.Assert(err, IsNil)
+	c.Assert(result.N, Equals, 44)
+}
+
 func (s *S) TestRemoveId(c *C) {
 	session, err := mgo.Dial("localhost:40001")
 	c.Assert(err, IsNil)