.

wcfs/internal/xbtree/δbtail.go

@@ -313,7 +313,9 @@ func (δTtail *ΔTtail) rebuild(δZtail *zodb.ΔTail, db *zodb.DB) (δtrackSet P
 
 	// go backwards and merge vδT <- treediff(lo..hi/trackNew)
 	vδZ := δZtail.Data()
-//	vδtrack := []*ΔPPTreeSubSet{}
+	for {
+		δtkeycov := &RangedKeySet{} // all keys coming into tracking set during this lo..hi scan
+		trackNewCur := trackNew.Clone()
 		for i := len(vδZ)-1; i>=0; i-- {
 			δZ := vδZ[i]
 
@@ -326,18 +328,34 @@ func (δTtail *ΔTtail) rebuild(δZtail *zodb.ΔTail, db *zodb.DB) (δtrackSet P
 				atPrev = δZtail.Tail()
 			}
 
-		δtrackNew, δtkeycov, err := δTtail.rebuild1(atPrev, δZ, trackNew, db)
+			δtrackNew, δtkeycov_, err := δTtail.rebuild1(atPrev, δZ, trackNewCur, db)
 			if err != nil {
 				return nil, err
 			}
 
-		trackNew.ApplyΔ(δtrackNew)
-		// FIXME use δtkeycov to recompute track coverage
-		_ = δtkeycov
+			trackNewCur.ApplyΔ(δtrackNew)
+			δtkeycov.UnionInplace(δtkeycov_)
 
 			// XXX update .KVAtTail, .lastRevOf
 		}
 
+		// an iteration closer to tail may turn out to add a key to the tracking set
+		// we have to recheck all entries past that revision for changes to that key
+		// for example:
+		//
+		//	XXX
+		//
+		// restart from head and cycle until set of tracked keys does not grow anymore
+		if δtkeycov.Empty() {
+			break
+		}
+
+		for _, r := δtkeycov.AllRanges() {
+		}
+
+	}
+
+
 /*
 	// trackNew was adjusted to correspond to @tail potentially growing its key coverage.
 	// Remap it back to @head and merge to .trackSet
@@ -346,8 +364,9 @@ func (δTtail *ΔTtail) rebuild(δZtail *zodb.ΔTail, db *zodb.DB) (δtrackSet P
 		trackNew.ApplyΔ(δtrack)
 	}
 	δBtail.trackSet.UnionInplace(trackNew)
-*/
 	return δtrackSet, nil
+*/
+	return trackNew
 }
 
 // rebuild1 rebuilds δT for single δZ.

wcfs/internal/zdata/δftail.go

@@ -160,7 +160,7 @@ func (δFtail *ΔFtail) Track(file *ZBigFile, blk int64, path []btree.LONode, zb
 		// XXX blk = ∞ from beginning ?
 		blk = xbtree.KeyMax
 	}
-	err := δFtail.δBtail.Track(blk, zblk != nil, path)
+	err := δFtail.δBtail.Track(blk, path)
 	if err != nil {
 		panic(err) // XXX -> error? errctx
 	}