diff --git a/tsdb/functions.go b/tsdb/functions.go
index b48e65e8d8..224d8d332b 100644
--- a/tsdb/functions.go
+++ b/tsdb/functions.go
@@ -88,8 +88,14 @@ func initializeMapFunc(c *influxql.Call) (mapFunc, error) {
 		}, nil
 
 	case "top", "bottom":
+		// Capture information from the call that the Map function will require
+		lit, _ := c.Args[len(c.Args)-1].(*influxql.NumberLiteral)
+		limit := int(lit.Val)
+		args := topCallArgs(c)
+		fields := c.Fields()
+
 		return func(itr Iterator) interface{} {
-			return MapTopBottom(itr, c)
+			return MapTopBottom(itr, limit, args, fields, len(c.Args), c.Name)
 		}, nil
 	case "percentile":
 		return MapEcho, nil
@@ -1445,16 +1451,12 @@ func (m *mapIter) Next() (time int64, value interface{}) {
 }
 
 // MapTopBottom emits the top/bottom data points for each group by interval
-func MapTopBottom(itr Iterator, c *influxql.Call) interface{} {
-	// Capture the limit if it was specified in the call
-	lit, _ := c.Args[len(c.Args)-1].(*influxql.NumberLiteral)
-	limit := int(lit.Val)
-
-	out := positionOut{callArgs: topCallArgs(c)}
+func MapTopBottom(itr Iterator, limit int, callArgs, fields []string, argCount int, callName string) interface{} {
+	out := positionOut{callArgs: callArgs}
 	out.points = make([]PositionPoint, 0, limit)
 	minheap := topBottomMapOut{
 		&out,
-		c.Name == "bottom",
+		callName == "bottom",
 	}
 	tagmap := make(map[string]PositionPoint)
 
@@ -1464,19 +1466,18 @@ func MapTopBottom(itr Iterator, c *influxql.Call) interface{} {
 
 	// buffer so we don't allocate every time through
 	var pp PositionPoint
-	if len(c.Args) > 2 {
+	if argCount > 2 {
 		// this is a tag aggregating query.
 		// For each unique permutation of the tags given,
 		// select the max and then fall through to select top of those
 		// points
 		for k, v := itr.Next(); k != -1; k, v = itr.Next() {
 			pp = PositionPoint{k, v, itr.Fields(), itr.Tags()}
-			callArgs := c.Fields()
 			tags := itr.Tags()
 			// TODO in the future we need to send in fields as well
 			// this will allow a user to query on both fields and tags
 			// fields will take the priority over tags if there is a name collision
-			key := tagkeytop(callArgs, nil, tags)
+			key := tagkeytop(fields, nil, tags)
 			p, ok := tagmap[key]
 			if !ok || minheap.positionPointLess(&p, &pp) {
 				tagmap[key] = pp
diff --git a/tsdb/functions_test.go b/tsdb/functions_test.go
index 71b1f3e9b2..a652e82fce 100644
--- a/tsdb/functions_test.go
+++ b/tsdb/functions_test.go
@@ -783,7 +783,12 @@ func TestMapTopBottom(t *testing.T) {
 		if test.skip {
 			continue
 		}
-		values := MapTopBottom(test.iter, test.call).(PositionPoints)
+		lit, _ := test.call.Args[len(test.call.Args)-1].(*influxql.NumberLiteral)
+		limit := int(lit.Val)
+		args := topCallArgs(test.call)
+		fields := test.call.Fields()
+
+		values := MapTopBottom(test.iter, limit, args, fields, len(test.call.Args), test.call.Name).(PositionPoints)
 		t.Logf("Test: %s", test.name)
 		if exp, got := len(test.exp.points), len(values); exp != got {
 			t.Errorf("Wrong number of values. exp %v got %v", exp, got)