Ensure DestUids is sorted

.travis.yml

 language: go
 go:
-- 1.7
+- 1.8
 dist: trusty
 sudo: required
 notifications:

algo/uidlist.go

@@ -27,6 +27,28 @@ type WriteIterator struct {
 
 }
 
+// AsList implements sort.Interface by for block lists
+type AsList struct{ l *task.List }
+
+func (s AsList) Len() int { return ListLen(s.l) }
+func (s AsList) Swap(i, j int) {
+	p, q := ridx(s.l, i)
+	m, n := ridx(s.l, j)
+	s.l.Blocks[p].List[q], s.l.Blocks[m].List[n] = s.l.Blocks[m].List[n], s.l.Blocks[p].List[q]
+}
+func (s AsList) Less(i, j int) bool {
+	p, q := ridx(s.l, i)
+	m, n := ridx(s.l, j)
+	return s.l.Blocks[p].List[q] < s.l.Blocks[m].List[n]
+}
+
+func Sort(ul *task.List) {
+	sort.Sort(AsList{ul})
+	for _, it := range ul.Blocks {
+		it.MaxInt = it.List[len(it.List)-1]
+	}
+}
+
 func NewWriteIterator(l *task.List, whence int) WriteIterator {
 	blen := len(l.Blocks)
 	var cur *task.Block

algo/uidlist_test.go

@@ -27,6 +27,30 @@ func newList(data []uint64) *task.List {
 	return SortedListToBlock(data)
 }
 
+func TestSort1(t *testing.T) {
+	input := newList([]uint64{55})
+	Sort(input)
+	require.Equal(t, BlockToList(input), []uint64{55})
+}
+
+func TestSort2(t *testing.T) {
+	input := newList([]uint64{})
+	Sort(input)
+	require.Equal(t, BlockToList(input), []uint64{})
+}
+
+func TestSort3(t *testing.T) {
+	input := newList([]uint64{55, 392, 1, 123})
+	Sort(input)
+	require.Equal(t, BlockToList(input), []uint64{1, 55, 123, 392})
+}
+
+func TestSort4(t *testing.T) {
+	input := newList([]uint64{55, 1, 100000})
+	Sort(input)
+	require.Equal(t, BlockToList(input), []uint64{1, 55, 100000})
+}
+
 func TestMergeSorted1(t *testing.T) {
 	input := []*task.List{
 		newList([]uint64{55}),

query/query.go

@@ -282,7 +282,6 @@ func (sg *SubGraph) preTraverse(uid uint64, dst, parent outputNode) error {
 					continue
 				}
 				uc := dst.New(fieldName)
-
 				if rerr := pc.preTraverse(childUID, uc, dst); rerr != nil {
 					if rerr.Error() == "_INV_" {
 						invalidUids[childUID] = true
@@ -638,13 +637,18 @@ func newGraph(ctx context.Context, gq *gql.GraphQuery) (*SubGraph, error) {
 	}
 	if len(gq.UID) > 0 {
 		o := new(task.List)
-		it := algo.NewWriteIterator(o, 0)
+		sg.SrcUIDs = new(task.List)
+		ito := algo.NewWriteIterator(o, 0)
+		itsg := algo.NewWriteIterator(sg.SrcUIDs, 0)
 		for _, uid := range gq.UID {
-			it.Append(uid)
+			ito.Append(uid)
+			itsg.Append(uid)
 		}
-		it.End()
-		sg.SrcUIDs = o
+		ito.End()
+		itsg.End()
 		sg.uidMatrix = []*task.List{o}
+		// User specified list may not be sorted.
+		algo.Sort(sg.SrcUIDs)
 	}
 	sg.values = createNilValuesList(1)
 	// Copy roots filter.
@@ -903,7 +907,17 @@ func (sg *SubGraph) fillVars(mp map[string]*task.List) {
 func ProcessGraph(ctx context.Context, sg, parent *SubGraph, rch chan error) {
 	var err error
 	if len(sg.Params.NeedsVar) != 0 && len(sg.SrcFunc) == 0 {
+		// Retain the actual order in uidMatrix. But sort the destUids.
 		sg.uidMatrix = []*task.List{sg.DestUIDs}
+		it := algo.NewListIterator(sg.DestUIDs)
+		var o task.List
+		wit := algo.NewWriteIterator(&o, 0)
+		for ; it.Valid(); it.Next() {
+			wit.Append(it.Val())
+		}
+		wit.End()
+		algo.Sort(&o)
+		sg.DestUIDs = &o
 	} else if len(sg.Attr) == 0 {
 		// If we have a filter SubGraph which only contains an operator,
 		// it won't have any attribute to work on.

query/query_test.go

@@ -470,6 +470,24 @@ func TestShortestPath(t *testing.T) {
 		js)
 }
 
+func TestShortestPathRev(t *testing.T) {
+	populateGraph(t)
+	query := `
+		{
+			A as shortest(from:23, to:1) {
+				friend 
+			}
+
+			me(var: A) {
+				name
+			}
+		}`
+	js := processToFastJSON(t, query)
+	require.JSONEq(t,
+		`{"me":[{"name":"Rick Grimes"},{"name":"Michonne"}]}`,
+		js)
+}
+
 func TestShortestPathWeightsMultiFacet_Error(t *testing.T) {
 	populateGraph(t)
 	query := `
@@ -2816,6 +2834,17 @@ func TestRootList1(t *testing.T) {
 	require.JSONEq(t, `{"me":[{"name":"Michonne"},{"name":"Rick Grimes"},{"name":"Glenn Rhee"},{"name":"Alice"}]}`, js)
 }
 
+func TestRootList2(t *testing.T) {
+	populateGraph(t)
+	query := `{
+	me(id:[0x01, 23, a.bc, 24]) {
+		name
+	}
+}`
+	js := processToFastJSON(t, query)
+	require.JSONEq(t, `{"me":[{"name":"Michonne"},{"name":"Rick Grimes"},{"name":"Alice"},{"name":"Glenn Rhee"}]}`, js)
+}
+
 func TestGeneratorMultiRootFilter1(t *testing.T) {
 	populateGraph(t)
 	query := `