comments and optimize potential rebalances

License: MIT
Signed-off-by: Jeromy <jeromyj@gmail.com>

merkledag/utils/diffenum.go

@@ -28,13 +28,24 @@ func DiffEnumerate(ctx context.Context, dserv node.NodeGetter, from, to *cid.Cid
 
 	sset := cid.NewSet()
 	for _, c := range diff {
-		if c.a == nil {
-			err := mdag.EnumerateChildrenAsync(ctx, mdag.GetLinksDirect(dserv), c.b, sset.Visit)
+		// Since we're already assuming we have everything in the 'from' graph,
+		// add all those cids to our 'already seen' set to avoid potentially
+		// enumerating them later
+		if c.bef != nil {
+			sset.Add(c.bef)
+		}
+	}
+	for _, c := range diff {
+		if c.bef == nil {
+			if sset.Has(c.aft) {
+				continue
+			}
+			err := mdag.EnumerateChildrenAsync(ctx, mdag.GetLinksDirect(dserv), c.aft, sset.Visit)
 			if err != nil {
 				return err
 			}
 		} else {
-			err := DiffEnumerate(ctx, dserv, c.a, c.b)
+			err := DiffEnumerate(ctx, dserv, c.bef, c.aft)
 			if err != nil {
 				return err
 			}
@@ -45,9 +56,12 @@ func DiffEnumerate(ctx context.Context, dserv node.NodeGetter, from, to *cid.Cid
 }
 
 type diffpair struct {
-	a, b *cid.Cid
+	bef, aft *cid.Cid
 }
 
+// getLinkDiff returns a changset (minimum edit distance style) between nodes
+// 'a' and 'b'. Currently does not log deletions as our usecase doesnt call for
+// this.
 func getLinkDiff(a, b node.Node) []diffpair {
 	have := make(map[string]*node.Link)
 	names := make(map[string]*node.Link)
@@ -65,11 +79,11 @@ func getLinkDiff(a, b node.Node) []diffpair {
 
 		match, ok := names[l.Name]
 		if !ok {
-			out = append(out, diffpair{b: l.Cid})
+			out = append(out, diffpair{aft: l.Cid})
 			continue
 		}
 
-		out = append(out, diffpair{a: match.Cid, b: l.Cid})
+		out = append(out, diffpair{bef: match.Cid, aft: l.Cid})
 	}
 	return out
 }

merkledag/utils/diffenum_test.go

@@ -70,6 +70,20 @@ var tg2 = map[string]ndesc{
 	"d": ndesc{},
 }
 
+var tg3 = map[string]ndesc{
+	"a1": ndesc{
+		"foo": "b",
+		"bar": "c",
+	},
+	"b": ndesc{},
+	"a2": ndesc{
+		"foo": "b",
+		"bar": "d",
+	},
+	"c": ndesc{},
+	"d": ndesc{},
+}
+
 func TestDiffEnumBasic(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -121,6 +135,7 @@ func assertCidList(a, b []*cid.Cid) error {
 	}
 	return nil
 }
+
 func TestDiffEnumFail(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -147,3 +162,29 @@ func TestDiffEnumFail(t *testing.T) {
 	}
 
 }
+
+func TestDiffEnumRecurse(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	nds := mkGraph(tg3)
+
+	ds := mdtest.Mock()
+	lgds := &getLogger{ds: ds}
+
+	for _, s := range []string{"a1", "a2", "b", "c", "d"} {
+		_, err := ds.Add(nds[s])
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	err := DiffEnumerate(ctx, lgds, nds["a1"].Cid(), nds["a2"].Cid())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = assertCidList(lgds.log, []*cid.Cid{nds["a1"].Cid(), nds["a2"].Cid(), nds["c"].Cid(), nds["d"].Cid()})
+	if err != nil {
+		t.Fatal(err)
+	}
+}