Server closes cursor when batch is 1. Use 2 instead.

Author: niemeyer

session.go

@@ -951,6 +951,10 @@ func (s *Session) SetSyncTimeout(d time.Duration) {
 // writing, MongoDB will use an initial size of min(100 docs, 4MB) on the
 // first batch, and 4MB on remaining ones.
 func (s *Session) SetBatch(n int) {
+	if n == 1 {
+		// Server interprets 1 as -1 and closes the cursor (!?)
+		n = 2
+	}
 	s.m.Lock()
 	s.queryConfig.op.limit = int32(n)
 	s.m.Unlock()
@@ -1591,6 +1595,10 @@ func (c *Collection) Create(info *CollectionInfo) error {
 // writing, MongoDB will use an initial size of min(100 docs, 4MB) on the
 // first batch, and 4MB on remaining ones.
 func (q *Query) Batch(n int) *Query {
+	if n == 1 {
+		// Server interprets 1 as -1 and closes the cursor (!?)
+		n = 2
+	}
 	q.m.Lock()
 	q.op.limit = int32(n)
 	q.m.Unlock()

session_test.go

@@ -927,8 +927,8 @@ func (s *S) TestQueryExplain(c *C) {
 	}
 
 	m := M{}
-	query := coll.Find(nil).Batch(1).Limit(2)
-	err = query.Batch(2).Explain(m)
+	query := coll.Find(nil).Limit(2)
+	err = query.Explain(m)
 	c.Assert(err, IsNil)
 	c.Assert(m["cursor"], Equals, "BasicCursor")
 	c.Assert(m["nscanned"], Equals, 2)
@@ -2841,3 +2841,26 @@ func (s *S) TestPipeOne(c *C) {
 	err = pipe.One(&result)
 	c.Assert(err, Equals, mgo.ErrNotFound)
 }
+
+func (s *S) TestBatch1(c *C) {
+	session, err := mgo.Dial("localhost:40001")
+	c.Assert(err, IsNil)
+	defer session.Close()
+
+	coll := session.DB("mydb").C("mycoll")
+
+	for i := 0; i < 3; i++ {
+		err := coll.Insert(M{"n": i})
+		c.Assert(err, IsNil)
+	}
+
+	var ns []struct{ N int }
+	err = coll.Find(nil).Batch(1).All(&ns)
+	c.Assert(err, IsNil)
+	c.Assert(len(ns), Equals, 3)
+
+	session.SetBatch(1)
+	err = coll.Find(nil).All(&ns)
+	c.Assert(err, IsNil)
+	c.Assert(len(ns), Equals, 3)
+}