.

wcfs/δbtail.go

@@ -818,19 +818,23 @@ func diffT(ctx context.Context, A, B *Tree, δZTC SetOid, trackIdx map[zodb.Oid]
 					// ( this does not give exact answer but should be a reasonable heuristic;
 					//   the diff is the same if heuristic does not work and we
 					//   look into and load more nodes to compute δ )
-					_, ok := BtrackIdx[acOid]
-					if !ok {
+					_, found := BtrackIdx[acOid]
+					if !found {
 						for {
 							blo  := Bv.Get(ac.lo)
 							bhi_ := Bv.Get(ac.hi_)
 							if blo != bhi_ {
 								break
 							}
+							_, ok := blo.node.(*Tree)
+							if !ok {
+								break // bucket
+							}
 							err = blo.node.PActivate(ctx);  /*X*/if err != nil { return nil, err }
 							defer blo.node.PDeactivate()
 
+							// XXX check for empty tree?
 							bchildren := Bv.Expand(blo)
-							found := false
 							for _, bc := range bchildren {
 									bcOid := bc.node.POid()
 									BtrackIdx[bcOid] = nodeTrack{parent: blo.node.POid()}
@@ -843,7 +847,7 @@ func diffT(ctx context.Context, A, B *Tree, δZTC SetOid, trackIdx map[zodb.Oid]
 							}
 						}
 					}
-					if ok {
+					if found {
 						// ac can be skipped
 						// XXX Bkqueue <- holes(ac.range \ bc.range)
 						continue