.

wcfs/zblk.go

@@ -526,7 +526,7 @@ func (bf *ZBigFile) Size(ctx context.Context) (_ int64, treePath []btree.LONode,
 	tailblk, ok, err := bf.blktab.VMaxKey(ctx, func(node btree.LONode) {
 		treePath = append(treePath, node)
 	})
-	if err != nil{
+	if err != nil {
 		return 0, nil, err
 	}
 	if !ok {

wcfs/δbtail.go

@@ -98,7 +98,8 @@ type ΔBtail struct {
 	db     *zodb.DB    // to open connections to load new/old tree|buckets
 
 	// tracked index: BTree|Bucket -> top tree element.
-	trackIdx map[zodb.Oid]SetTree // oid -> {} roots	XXX root -> oid
+	// XXX allow only single root (else it is "tree corrupt") ?
+	trackIdx map[zodb.Oid]SetTree // oid -> {} roots XXX root -> oid
 
 	// tracked objects that are not yet taken into account in current δBtail
 	trackNew map[zodb.Oid]struct{}	// XXX SetOid
@@ -165,7 +166,7 @@ func (δBtail *ΔBtail) Tail() zodb.Tid { return δBtail.δZtail.Tail() }
 // Track adds tree path to tracked set.
 //
 // path[0] signifies tree root.
-// All path elemens must be Tree except last one which must be Bucket.
+// All path elements must be Tree except last one which must be Bucket.
 //
 // XXX δBtail is rebuild to also include keys corresponding to added nodes.
 //
@@ -173,7 +174,16 @@ func (δBtail *ΔBtail) Tail() zodb.Tid { return δBtail.δZtail.Tail() }
 // XXX path -> []oid ?
 //
 // XXX catch cycles on add?
-func (δBtail *ΔBtail) Track(path []Node) {	// XXX Tree|Bucket; path[0] = root
+type TrackFlags int
+const (
+	// TrackMaxKey
+	// - indicates that provided path is currently the rightmost arm of the tree, and
+	// - requests that changes to max key of the tree to be covered by δBtail from now on.
+	TrackMaxKey TrackFlags = 1 << iota
+
+	// XXX TrackMinKey (we don't need it in WCFS)
+)
+func (δBtail *ΔBtail) Track(path []Node, flags TrackFlags) {	// XXX Tree|Bucket; path[0] = root
 	l := len(path)
 	if l == 0 {
 		panic("empty path")

wcfs/δbtail_test.go

@@ -46,6 +46,8 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+const kInf Key = 10000 // inf key (TeX hack)
+
 // XXX move infrastructure -> δbtail_treegen_test.go ?
 
 // TreeGenSrv represents connection to running `treegen ...` server.
@@ -328,7 +330,7 @@ func xverifyΔBTail(t *testing.T, subj string, db *zodb.DB, treeRoot zodb.Oid, a
 	d12 := kvdiff(kv1, kv2)
 
 	// verify transition at1->at2 for all initial states of tracked {keys} from kv1 + kv2 + ∞
-	allKeys := SetKey{}; allKeys.Add(10000) // inf, simulating ZBigFile.Size() query
+	allKeys := SetKey{}; allKeys.Add(kInf) // inf, simulating ZBigFile.Size() query
 	for k := range kv1 { allKeys.Add(k) }
 	for k := range kv2 { allKeys.Add(k) }
 	allKeyv := allKeys.Elements()
@@ -336,19 +338,26 @@ func xverifyΔBTail(t *testing.T, subj string, db *zodb.DB, treeRoot zodb.Oid, a
 		return allKeyv[i] < allKeyv[j]
 	})
 
+	// maxkey among kv1+kv2
+	// it must be present in δB if maxkey tracking is requested.
+	maxKey := -kInf
+	if l := len(allKeyv); l > 0 {
+		maxKey = allKeyv[l-1]
+	}
+
 	for kidx := range IntSets(len(allKeyv)) {
 		keys := SetKey{}
 		for _, idx := range kidx {
 			keys.Add(allKeyv[idx])
 		}
 
-		xverifyΔBTail1(t, subj, db, treeRoot, at1,at2, d12, δZ, keys)
+		xverifyΔBTail1(t, subj, db, treeRoot, at1,at2, d12, maxKey, δZ, keys)
 	}
 }
 
 // xverifyΔBTail1 verifies how ΔBTail handles ZODB update at1->at2 from initial
 // tracked state defined by initialTrackedKeys.
-func xverifyΔBTail1(t *testing.T, subj string, db *zodb.DB, treeRoot zodb.Oid, at1,at2 zodb.Tid, d12 map[Key]string, δZ *zodb.EventCommit, initialTrackedKeys SetKey) {
+func xverifyΔBTail1(t *testing.T, subj string, db *zodb.DB, treeRoot zodb.Oid, at1,at2 zodb.Tid, d12 map[Key]string, maxKey Key, δZ *zodb.EventCommit, initialTrackedKeys SetKey) {
 	X := exc.Raiseif
 	assert := require.New(t)
 
@@ -368,13 +377,20 @@ func xverifyΔBTail1(t *testing.T, subj string, db *zodb.DB, treeRoot zodb.Oid,
 	xtree, err := zconn.Get(ctx, treeRoot);	X(err)
 	ztree := xtree.(*Tree)
 
+	trackingMaxKey := false
 	for k := range initialTrackedKeys {
 		path := []Node{}
 		_, _, err = ztree.VGet(ctx, k, func(node Node) {
 			path = append(path, node)
 		}); X(err)
 
-		δbtail.Track(path)
+		// kInf imitates ZBigFile.Size() request, which enables maxkey tracking.
+		trackFlags := TrackFlags(0)
+		if k == kInf {
+			trackFlags = TrackMaxKey
+			trackingMaxKey = true
+		}
+		δbtail.Track(path, trackFlags)
 	}
 
 	// δbtail <- δZ
@@ -409,6 +425,7 @@ func xverifyΔBTail1(t *testing.T, subj string, db *zodb.DB, treeRoot zodb.Oid,
 	// changed keys, that are
 	// - in tracked set	 -> must be present in δT
 	// - outside tracked set -> may  be present in δT
+	// - maxkey              -> must be present in δT if trackingMaxKey
 
 	// δT is subset of d12
 	for k := range δT {
@@ -420,9 +437,10 @@ func xverifyΔBTail1(t *testing.T, subj string, db *zodb.DB, treeRoot zodb.Oid,
 
 	// k ∈ tracked set ->  must be present in δT
 	// k ∉ tracked set ->  may  be present in δT
+	// k==max && tracking maxKey -> k must be present in δT
 	for k := range d12 {
 		_, inδT := δT[k]
-		if initialTrackedKeys.Has(k) {
+		if initialTrackedKeys.Has(k) || (k == maxKey && trackingMaxKey) {
 			if !inδT {
 				badf("δT: [%v] is missing", k)
 			}

wcfs/δftail.go

@@ -134,7 +134,11 @@ func (δFtail *ΔFtail) Tail() zodb.Tid { return δFtail.δBtail.Tail() }
 //
 // A root can be associated with several files (each provided on different Track call).
 func (δFtail *ΔFtail) Track(file *BigFile, blk int64, path []btree.LONode, zblk zBlk) {
-	δFtail.δBtail.Track(path)
+	δbTrackFlags := TrackFlags(0)
+	if blk == -1 {
+		δbTrackFlags = TrackMaxKey
+	}
+	δFtail.δBtail.Track(path, δbTrackFlags)
 	root := path[0].(*btree.LOBTree)
 	files, ok := δFtail.fileIdx[root.POid()]
 	if !ok {