X wcfs/xbtree: treediff(ø, b)

wcfs/internal/xbtree/pptreesubset.go

@@ -131,32 +131,6 @@ func (S PPTreeSubSet) AddPath(path []zodb.Oid) {
 	}
 }
 
-// AddNodePath is a convenience wrapper to call AddPath starting from Nodes instead of Oids.
-func (S PPTreeSubSet) AddNodePath(path []Node) {
-	// assert path = Tree Tree ... Tree Bucket
-	l := len(path)
-	switch {
-	case l == 0:
-		panic("empty path")
-	case l == 1:
-		// must be empty Tree
-		_ = path[0].(*Tree)
-	default:
-		// must be Tree Tree ... Tree Bucket
-		for _, node := range path[:l-1] {
-			_ = node.(*Tree)
-		}
-		_ = path[l-1].(*Bucket)
-	}
-
-	oidv := make([]zodb.Oid, l)
-	for i, node := range path {
-		oidv[i] = node.POid()
-	}
-	S.AddPath(oidv)
-}
-
-
 // ---- Union/Difference ----
 
 // UnionInplace sets A = PP(A.leafs | B.leafs)

wcfs/internal/xbtree/treediff.go

@@ -468,12 +468,18 @@ func diffT(ctx context.Context, A, B *Tree, δZTC SetOid, trackSet PPTreeSubSet,
 	δtrack = &ΔPPTreeSubSet{Del: PPTreeSubSet{}, Add: PPTreeSubSet{}, δnchildNonLeafs: map[zodb.Oid]int{}}
 	defer tracef("  -> δ: %v\n", δ)
 
-	if A==nil && B==nil {
-		panic("TODO: verify it is covered by tests")
+	if A == nil && B == nil {
 		return δ, δtrack, nil // ø changes
 	}
 
-	// XXX A!=nil && B!=nil  ->  assert A.POid() == B.POid()
+	// assert A.oid == B.oid
+	if A != nil && B != nil {
+		Aoid := A.POid()
+		Boid := B.POid()
+		if Aoid != Boid {
+			panicf("A.oid (%s)  !=  B.oid (%s)", Aoid, Boid)
+		}
+	}
 
 	var ABoid zodb.Oid
 	if A != nil {
@@ -493,10 +499,12 @@ func diffT(ctx context.Context, A, B *Tree, δZTC SetOid, trackSet PPTreeSubSet,
 		δtrack.Add.AddPath(ABpath)
 	}
 
-	if A == nil { panic("A is nil") }	// TODO -> art. ø tree
+	// A|B == nil  -> artificial empty tree
+	if A == nil {
+		A = zodb.NewPersistent(reflect.TypeOf(Tree{}), /*jar*/nil).(*Tree)
+	}
 	Bempty := false
 	if B == nil {
-		// artificial empty tree
 		B = zodb.NewPersistent(reflect.TypeOf(Tree{}), /*jar*/nil).(*Tree)
 		Bempty = true
 	}

wcfs/internal/xbtree/xbtree.go

@@ -42,3 +42,29 @@ func tracef(format string, argv ...interface{}) {
 		fmt.Printf(format, argv...)
 	}
 }
+
+// nodePathToPath converts path from []Node to []Oid.
+// XXX place = ?
+func nodePathToPath(nodePath []Node) (path []zodb.Oid) {
+	// assert nodePath = Tree Tree ... Tree Bucket
+	l := len(nodePath)
+	switch {
+	case l == 0:
+		panic("empty path")
+	case l == 1:
+		// must be empty Tree
+		_ = nodePath[0].(*Tree)
+	default:
+		// must be Tree Tree ... Tree Bucket
+		for _, node := range nodePath[:l-1] {
+			_ = node.(*Tree)
+		}
+		_ = nodePath[l-1].(*Bucket)
+	}
+
+	path = make([]zodb.Oid, l)
+	for i, node := range nodePath {
+		path[i] = node.POid()
+	}
+	return path
+}

wcfs/internal/xbtree/δbtail.go

@@ -224,15 +224,20 @@ func (δBtail *ΔBtail) Tail() zodb.Tid { return δBtail.δZtail.Tail() }
 // XXX path -> []oid ?
 //
 // XXX catch cycles on add?
-func (δBtail *ΔBtail) Track(key Key, keyPresent bool, path []Node) error { // XXX Tree|Bucket; path[0] = root
-	// XXX assert Tree Tree ... Tree Bucket		XXX AddNodePath does that
-	root := path[0].(*Tree).POid()
+func (δBtail *ΔBtail) Track(key Key, keyPresent bool, nodePath []Node) error { // XXX Tree|Bucket; path[0] = root
+
+	path := nodePathToPath(nodePath)
 
 	pathv := []string{}
-	for _, node := range path { pathv = append(pathv, vnode(node)) }
+	for _, node := range nodePath { pathv = append(pathv, vnode(node)) }
 	tracef("Track [%v] %s\n", key, strings.Join(pathv, " -> "))
 
-	δBtail.trackNew.AddNodePath(path)
+	return δBtail.track(key, keyPresent, path)
+}
+
+func (δBtail *ΔBtail) track(key Key, keyPresent bool, path []zodb.Oid) error {
+	root := path[0]
+	δBtail.trackNew.AddPath(path)
 
 	// track is track of path[-1]  (i.e. leaf)
 

wcfs/internal/xbtree/δbtail_test.go

@@ -608,11 +608,6 @@ func xverifyΔBTail_Update(t *testing.T, subj string, db *zodb.DB, treeRoot zodb
 	// verify transition at1->at2 for all initial states of tracked {keys} from kv1 + kv2 + ∞
 
 	t.Run(fmt.Sprintf("Update/%s→%s", t1.tree, t2.tree), func(t *testing.T) {
-		if t1.tree == DEL {
-			// Track(k) -> Update  ; requires that tree exists at Track time
-			t.Skip("Track(tree1) needs tree1 to exist")	// XXX just limit trackKeys to ø instead ?
-		}
-
 		allKeys := allTestKeys(t1, t2)
 		allKeyv := allKeys.SortedElements()
 
@@ -668,13 +663,29 @@ func xverifyΔBTail_Update1(t *testing.T, subj string, db *zodb.DB, treeRoot zod
 	zconn, err := db.Open(ctx, &zodb.ConnOptions{At: at1});	X(err)
 	δbtail := NewΔBtail(zconn.At(), db)
 
-	xtree, err := zconn.Get(ctx, treeRoot);	X(err)
-	ztree := xtree.(*Tree)
+	xtree, err := zgetNodeOrNil(ctx, zconn, treeRoot); X(err)
+	var ztree *Tree // = nil if treeRoot was deleted
+	if xtree != nil {
+		ztree = xtree.(*Tree)
+	}
 
 	kadjTracked = SetKey{} // kadj[Tracked]  (all keys adjacent to tracked keys)
 	for k := range initialTrackedKeys {
-		_, ok, path, err := ZTreeGetBlkData(ctx, ztree, k);  X(err)
-		err = δbtail.Track(k, ok, path); X(err)
+		if ztree != nil {
+			_, ok, path, err := ZTreeGetBlkData(ctx, ztree, k);  X(err)
+			err = δbtail.Track(k, ok, path); X(err)
+		} else {
+			// if treeRoot is deleted - add it to tracked set with every key
+			// being a hole. This aligns with the following situation
+			//
+			//	T1 -> ø -> T2
+			//
+			// where after T1->ø, even though the tree becomes deleted, its root
+			// continues to be tracked and all keys migrate to holes in the
+			// tracking set. By aligning initial state to the same as after
+			// T1->ø, we test what will happen on ø->T2.
+			err = δbtail.track(k, false, []zodb.Oid{treeRoot});  X(err)
+		}
 
 		kadjTracked.Update(kadj[k])
 	}