X Track should be nop if keycov/path is already in krebuildJobs

wcfs/internal/xbtree/δbtail.go

@@ -248,8 +248,9 @@ type _ΔTtail struct {
 
 // _RebuildJob represents currently in-progress vδT rebuilding job.
 type _RebuildJob struct {
-	ready chan struct{} // closed when job completes
-	err   error
+	trackNew blib.PPTreeSubSet // rebuilding for this trackNew
+	ready    chan struct{}     // closed when job completes
+	err      error
 }
 
 // _ΔBroots represents roots-only part of ΔB.
@@ -437,35 +438,49 @@ func (δBtail *ΔBtail) track(path []zodb.Oid, keycov KeyRange) {
 	}
 
 	root := path[0]
-
-	// nothing to do if keycov is already tracked
 	leaf := path[len(path)-1]
-	if δBtail.trackSet.Has(leaf) {
-		tracefΔBtail("->T: nop\n")
-		path_ := δBtail.trackSet.Path(leaf)
+
+	// assertSamePathToLeaf asserts that T.Path(leaf) == path.
+	assertSamePathToLeaf := func(T blib.PPTreeSubSet, Tname string) {
+		path_ := T.Path(leaf)
 		if !pathEqual(path, path_) {
-			panicf("BUG: keycov %s is already tracked via path=%v\ntrack requests path=%v", keycov, path_, path)
+			panicf("BUG: keycov %s is already in %s via path=%v\ntrack requests path=%v", keycov, Tname, path_, path)
 		}
+	}
+
+	// nothing to do if keycov is already tracked
+	if δBtail.trackSet.Has(leaf) {
+		tracefΔBtail("->T: nop  (already in trackSet)\n")
+		assertSamePathToLeaf(δBtail.trackSet, "trackSet")
 		return
 	}
 
-	// queue path into trackNew, if not there already
 	δTtail, ok := δBtail.byRoot[root]
 	if !ok {
 		δTtail = newΔTtail()
 		δBtail.byRoot[root] = δTtail
 	}
 
-	if δTtail.trackNew.Has(leaf) {
-		tracefΔBtail("->T: nop\n")
-		path_ := δTtail.trackNew.Path(leaf)
-		if !pathEqual(path, path_) {
-			panicf("BUG: keycov %s is already in trackNew via path=%v\ntrack requests path=%v", keycov, path_, path)
+	// nothing to do if keycov is already queued to be tracked in trackNew or krebuildJobs
+	inJobs := δTtail.krebuildJobs.IntersectsRange(keycov)
+	if inJobs {
+		tracefΔBtail("->T: nop  (already in krebuildJobs)\n")
+		job, r, ok := δTtail.krebuildJobs.Get_(keycov.Lo)
+		if !(ok && r == keycov) {
+			panicf("BUG: keycov is present in krebuildJobs only partly\nkeycov: %s\nkrebuildJobs: %v",
+			       keycov, δTtail.krebuildJobs)
 		}
+		assertSamePathToLeaf(job.trackNew, "job.trackNew")
 		return
 	}
-	// XXX also check if keycov ∈ krebuildJobs
 
+	if δTtail.trackNew.Has(leaf) {
+		tracefΔBtail("->T: nop  (already in trackNew)\n")
+		assertSamePathToLeaf(δTtail.trackNew, "trackNew")
+		return
+	}
+
+	// keycov not in trackSet/trackNew/krebuildJobs -> queue it into trackNew
 	δBtail.trackNewRoots.Add(root)
 	δTtail.trackNew.AddPath(path)
 	δTtail.ktrackNew.AddRange(keycov)
@@ -577,13 +592,14 @@ func (δTtail *_ΔTtail) _rebuild(root zodb.Oid, δBtail *ΔBtail) (err error) {
 }
 func (δTtail *_ΔTtail) __rebuild(root zodb.Oid, δBtail *ΔBtail, releaseLock bool) (err error) {
 	defer xerr.Contextf(&err, "ΔBtail._rebuild root<%s>", root)
-	job := &_RebuildJob{ready: make(chan struct{})}
 
 	trackNew  := δTtail.trackNew
 	ktrackNew := δTtail.ktrackNew
 	δTtail.trackNew  = blib.PPTreeSubSet{}
 	δTtail.ktrackNew = blib.RangedKeySet{}
 
+	job := &_RebuildJob{trackNew: trackNew, ready: make(chan struct{})}
+
 	// krebuildJobs += ktrackNew
 	for _, r := range ktrackNew.AllRanges() {
 		// assert krebuildJobs ^ r = ø