X Switch GetAt to vδTSnapForTrackedKey

wcfs/internal/xbtree/δbtail.go

@@ -319,13 +319,17 @@ func (δBtail *ΔBtail) Tail() zodb.Tid { return δBtail.δZtail.Tail() }
 // All path elements must be Tree except last one which, for non-empty tree, must be Bucket.
 //
 // Objects in the path must be with .PJar().At() == .Head()
+//
+// XXX put keycov back to come first?
 func (δBtail *ΔBtail) Track(nodePath []Node, keycov KeyRange) {
+/* XXX kill
 	if traceΔBtail {
 		pathv := []string{}
 		for _, node := range nodePath { pathv = append(pathv, vnode(node)) }
 		tracefΔBtail("\nTrack %s %s\n", keycov, strings.Join(pathv, " -> "))
 		tracefΔBtail("trackSet: %s\n", δBtail.trackSet) // XXX locking
 	}
+*/
 
 	head := δBtail.Head()
 	for _, node := range nodePath {
@@ -367,6 +371,13 @@ func nodePathToPath(nodePath []Node) (path []zodb.Oid) {
 func (δBtail *ΔBtail) track(path []zodb.Oid, keycov KeyRange) {
 	// XXX locking
 
+	if traceΔBtail {
+		pathv := []string{}
+		for _, node := range path { pathv = append(pathv, node.String()) }
+		tracefΔBtail("\nTrack %s %s\n", keycov, strings.Join(pathv, " -> "))
+		tracefΔBtail("trackSet: %s\n", δBtail.trackSet)
+	}
+
 	// first normalize path: remove embedded bucket and check if it was an
 	// empty artificial tree. We need to do the normalization because we
 	// later check whether leaf path[-1] ∈ trackSet and without
@@ -388,6 +399,7 @@ func (δBtail *ΔBtail) track(path []zodb.Oid, keycov KeyRange) {
 		}
 		return
 	}
+	// XXX also check if leaf   ∈ trackNew      ?
 	// XXX also check if keycov ∈ krebuildJobs
 
 	// queue path into trackNew
@@ -432,10 +444,15 @@ func (δBtail *ΔBtail) rebuild1IfNeeded(root zodb.Oid) error {
 	return δBtail.rebuild1(root)
 }
 
-// vδTSnapWithTrackedKey returns vδT snapshot for root that takes into account all previous Track requests related to key.
-func (δBtail *ΔBtail) vδTSnapWithTrackedKey(root zodb.Oid, key Key) (vδT []ΔTree, err error) {
+// vδTSnapForTrackedKey returns vδT snapshot for root that takes into account at least all previous Track requests related to key.
+func (δBtail *ΔBtail) vδTSnapForTrackedKey(root zodb.Oid, key Key) (vδT []ΔTree, err error) {
 	// XXX δBtail.lock
 	δTtail := δBtail.byRoot[root] // must be there
+	if δTtail == nil {
+		panicf("δBtail: root<%s> not tracked", root)
+	}
+
+	// TODO key not tracked	-> panic  (check key ∈ lastRevOf)
 
 	if !δTtail.ktrackNew.Has(key) {
 		// key ∉ ktrackNew
@@ -461,7 +478,6 @@ func (δBtail *ΔBtail) vδTSnapWithTrackedKey(root zodb.Oid, key Key) (vδT []
 	// key ∈ ktrackNew  ->  this goroutine becomes responsible to start rebuilding vδT for it
 	// lauch rebuild job for all keys queued in ktrackNew so far
 	err = δTtail._runRebuildJob(root, δBtail)
-
 	if err != nil {
 		return nil, err
 	}
@@ -473,10 +489,13 @@ func (δBtail *ΔBtail) vδTSnapWithTrackedKey(root zodb.Oid, key Key) (vδT []
 	return vδT, nil
 }
 
-// vδTSnapWithTracked returns vδT snapshot for root that takes into account all previous Track requests.
-func (δBtail *ΔBtail) vδTSnapWithTracked(root zodb.Oid) (vδT []ΔTree, err error) {
+// vδTSnapForTracked returns vδT snapshot for root that takes into account all previous Track requests.
+func (δBtail *ΔBtail) vδTSnapForTracked(root zodb.Oid) (vδT []ΔTree, err error) {
 	// XXX δBtail.lock
 	δTtail := δBtail.byRoot[root] // must be there
+	if δTtail == nil {
+		panicf("δBtail: root<%s> not tracked", root)
+	}
 
 	// prepare to wait for all already running jobs, if any
 	wg := xsync.NewWorkGroup(context.Background())
@@ -543,7 +562,7 @@ func (δTtail *_ΔTtail) _runRebuildJob(root zodb.Oid, δBtail *ΔBtail) (err er
 	}
 
 	// merge rebuild result
-	if err != nil {
+	if err == nil {
 		// XXX comment about RCU snapshot
 		δTtail.vδT = vδTClone(δTtail.vδT)
 		δrevSet := vδTMergeInplace(&δTtail.vδT, vδTnew)
@@ -561,8 +580,8 @@ func (δTtail *_ΔTtail) _runRebuildJob(root zodb.Oid, δBtail *ΔBtail) (err er
 }
 
 /*
-// vδTSnapWithTracked returns vδT snapshot for root that takes into account all previous Track requests.
-func (δBtail *ΔBtail) vδTSnapWithTracked(root zodb.Oid) (vδT []ΔTree, err error) {
+// vδTSnapForTracked returns vδT snapshot for root that takes into account all previous Track requests.
+func (δBtail *ΔBtail) vδTSnapForTracked(root zodb.Oid) (vδT []ΔTree, err error) {
 	// XXX δBtail.lock
 	δTtail := δBtail.byRoot[root] // must be there
 
@@ -817,6 +836,8 @@ func vδTBuild(root zodb.Oid, trackNew blib.PPTreeSubSet, δZtail *zodb.ΔTail,
 		}
 	}
 
+	tracefΔBtail("-> vδT:        %v\n", vδT)
+	tracefΔBtail("-> trackNew*:  %v\n", trackNew)
 	return vδT, trackNew, nil
 }
 
@@ -1231,32 +1252,50 @@ func (δTtail *_ΔTtail) forgetPast(revCut zodb.Tid) {
 func (δBtail *ΔBtail) GetAt(root zodb.Oid, key Key, at zodb.Tid) (value Value, rev zodb.Tid, valueExact, revExact bool, err error) {
 	defer xerr.Contextf(&err, "δBtail: root<%s>: get %d @%s", root, key, at)
 
+	if traceΔBtail {
+		tracefΔBtail("\nGet root<%s>[%s] @%s\n", root, kstr(key), at)
+		defer func() {
+			vexact := ""
+			rexact := ""
+			if !valueExact {
+				vexact = "~"
+			}
+			if !revExact {
+				rexact = "~"
+			}
+			tracefΔBtail("-> value: %s%s  rev: @%s%s\n", value, vexact, rev, rexact)
+		}()
+	}
+
 	tail := δBtail.Tail()
 	head := δBtail.Head()
 	if !(tail < at && at <= head) {
 		panicf("at out of bounds: at: @%s,  (tail, head] = (@%s, @%s]", at, tail, head)
 	}
 
-	// XXX locking
+//	// XXX locking
 
 	value = VDEL
 	valueExact = false
 	rev = tail
 	revExact = false
 
-	// XXX need to rebuild only if key was not rebuilt yet
-	// XXX need to rebuild only for key, not for whole trackNew
+	vδT, err := δBtail.vδTSnapForTrackedKey(root, key)
+//	// XXX need to rebuild only if key was not rebuilt yet
+//	// XXX need to rebuild only for key, not for whole trackNew
 //	err = δBtail.rebuild1KeyIfNeeded(root, key)	XXX reenable
-	err = δBtail.rebuild1IfNeeded(root)
+//	err = δBtail.rebuild1IfNeeded(root)
 	if err != nil {
 		return value, rev, valueExact, revExact, err
 	}
 
-	δTtail := δBtail.byRoot[root]
-	if δTtail == nil {
-		panicf("δBtail: root<%s> not tracked", root)
-	}
-	vδT := δTtail.vδT
+	debugfΔBtail("  vδT: %v\n", vδT)
+
+//	δTtail := δBtail.byRoot[root]
+//	if δTtail == nil {
+//		panicf("δBtail: root<%s> not tracked", root)
+//	}
+//	vδT := δTtail.vδT
 	// TODO key not tracked	-> panic  (check key ∈ lastRevOf  -- see vvv)
 
 	// TODO -> index lastRevOf(key) | linear scan ↓ looking for change ≤ at