.

wcfs/δbtail.go

@@ -40,6 +40,8 @@ type Tree   = btree.LOBTree
 type Bucket = btree.LOBucket
 type Node   = btree.LONode
 
+type BucketEntry = btree.LOBucketEntry
+
 type Key    = int64
 const KeyMax Key = math.MaxInt64
 type Value  = zodb.Oid // assumes key points to IPersistent
@@ -498,16 +500,22 @@ func diffB(ctx context.Context, a, b *Bucket) (δ map[Key]Value, err error) {
 
 	// XXX a/b = nil - means del/add -> handle
 
-	err = a.PActivate(ctx);  if err != nil { return nil, err }
-	defer a.PDeactivate()
-	err = b.PActivate(ctx);  if err != nil { return nil, err }
-	defer b.PDeactivate()
+	var av []BucketEntry
+	var bv []BucketEntry
+	if a != nil {
+		err = a.PActivate(ctx);  if err != nil { return nil, err }
+		defer a.PDeactivate()
+		av  = a.Entryv() // key↑
+	}
+	if b != nil {
+		err = b.PActivate(ctx);  if err != nil { return nil, err }
+		defer b.PDeactivate()
+		bv  = b.Entryv() // key↑
+	}
 
 	//fmt.Println("> diffB", a.POid())
 	//defer fmt.Println("< diffB")
 
-	av := a.Entryv() // key↑
-	bv := b.Entryv() // key↑
 	δ   = map[Key]Value{}
 	//fmt.Println("av:", av)
 	//fmt.Println("bv:", bv)