.

wcfs/δbtail.go

@@ -412,6 +412,21 @@ func (A trackIndex) xDifferenceInplace(B trackIndex) {
 
 	δnchild := map[zodb.Oid]int{}
 
+/* XXX kill
+	// remove (A^B).leafs and thier parents
+	// we have to start (A^B).leafs - not from B.leafs - because B can
+	// contain non-leaf to remove from A, with that non-leaf having
+	// children in B, that are not present in A:
+	//
+	//       c      c
+	//       |      |
+	//      11     11
+	//       |      |
+	//      14     14
+	//       |       \
+	//      15       16
+	AB := B.Intersect(A)
+*/
 	// remove B.leafs and thier parents
 	for oid, t2 := range B {
 		if t2.nchild != 0 {
@@ -433,6 +448,7 @@ func (A trackIndex) xDifferenceInplace(B trackIndex) {
 		}
 
 		delete(A, oid)
+		// XXX + return A.nchild in removedNonLeafs  {} oid -> nchild ?  (probably no)
 		if t.parent != zodb.InvalidOid {
 			δnchild[t.parent] -= 1
 		}
@@ -483,10 +499,13 @@ func (A trackIndex) xUnionInplace(B trackIndex) {
 // fixup performs scheduled δnchild adjustment.
 // XXX place
 func (A trackIndex) fixup(δnchild map[zodb.Oid]int) {
+	A.xfixup(+1, δnchild)
+}
+func (A trackIndex) xfixup(sign int, δnchild map[zodb.Oid]int) {
 	gcq := []zodb.Oid{}
 	for oid, δnc := range δnchild {
 		t := A[oid]	// XXX t can be nil -> XXX no must be there as A is connected
-		t.nchild += δnc
+		t.nchild += sign*δnc
 		if t.nchild == 0 && /* not root node */t.parent != zodb.InvalidOid {
 			gcq = append(gcq, oid)
 		}
@@ -560,9 +579,10 @@ func (tidx trackIndex) ApplyΔ(δ *δtrackIndex) {
 	δ.Add.verify()
 	defer tidx.verify()
 
+	tidx.xfixup(-1, δ.δnchildNonLeafs)
 	tidx.xDifferenceInplace(δ.Del)
 	tidx.xUnionInplace(δ.Add)
-	tidx.fixup(δ.δnchildNonLeafs)
+	tidx.xfixup(+1, δ.δnchildNonLeafs)
 }
 
 // treeSetKey represents ordered set of keys.

wcfs/δbtail_test.go

@@ -1430,7 +1430,7 @@ func TestΔBTail(t *testing.T) {
 		"T2,5/B1:a-B2:b,4:d-B8:h", // XXX add A
 
 		// found by AllStructs ([1] is not changed, but because B1 is
-		// unlinked and 1 migrates to othe bucket, changes in that
+		// unlinked and 1 migrates to other bucket, changes in that
 		// other bucket must be included into δT)
 		"T1,2/B0:e-B1:d-B2:g,3:a",
 		"T1/B0:d-B1:d,2:d",
@@ -1485,6 +1485,9 @@ func TestΔBTail(t *testing.T) {
 		"T/T1/T-T2/B0:e-B1:f-B2:g",
 
 		// ApplyΔ -> xunion: node is reachable from multiple parents
+		// ( because xdifference did not remove common non-leaf node
+		//   under which there were also other changed, but not initially
+		//   tracked, node )
 		"T4/T1-T/T-T2-B4:c/T-T-T/B0:f-B1:h-B2:g,3:b",
 		"T1/T-T/T-T2/T-T-T/B0:f-B1:h-B2:f",
 		// ----//----