.

wcfs/δbtail.go

@@ -257,7 +257,9 @@ func (δBtail *ΔBtail) Track(key Key, keyPresent bool, path []Node, flags Track
 			panicf("node %s is reachable from multiple parents: %s %s",
 				oid, track.parent, parent)
 		}
-		track.trackedKeys.Add(key)
+		if track.trackedKeys != nil { // root always covers [-∞, ∞)
+			track.trackedKeys.Add(key)
+		}
 		parent = oid
 	}
 
@@ -297,20 +299,32 @@ func (δBtail *ΔBtail) Update(δZ *zodb.EventCommit) (_ ΔB, err error) {
 	fmt.Printf("trackIdx: %v\n", δBtail.trackIdx)
 
 	// {} root -> {oid} changed under that root in tracked set
+	rootOf := func(node zodb.Oid) (root zodb.Oid, ok bool) {
+		track, ok := δBtail.trackIdx[node]
+		if !ok {
+			return zodb.InvalidOid, false
+		}
+
+		for track.parent != zodb.InvalidOid {
+			node = track.parent
+			track = δBtail.trackIdx[node] // must be present
+		}
+		return node, true
+
+	}
 	δZByRoot := map[zodb.Oid]SetOid{}
 	for _, oid := range δZ.Changev {
-		roots, ok := δBtail.trackIdx[oid]
+		root, ok := rootOf(oid)
 		if !ok {
 			continue
 		}
-		for root := range roots {
-			δZT, ok := δZByRoot[root]
-			if !ok {
-				δZT = SetOid{}
-				δZByRoot[root] = δZT
-			}
-			δZT.Add(oid)
+
+		δZT, ok := δZByRoot[root]
+		if !ok {
+			δZT = SetOid{}
+			δZByRoot[root] = δZT
 		}
+		δZT.Add(oid)
 	}
 	fmt.Println("δZByRoot:", δZByRoot)