.

wcfs/internal/xbtree/δbtail.go

@@ -22,6 +22,53 @@
 // TODO move -> btree when ΔTail matures.
 package xbtree
 
+// δ(BTree) notes
+// ==============
+//
+// input: BTree, (@new, []oid)  ->  find out δ(BTree) i.e. {-k(v), +k'(v'), ...}
+//
+// - oid ∈ Bucket
+// - oid ∈ BTree
+//
+// Bucket:
+//
+//      old = {k  -> v}
+//      new = {k' -> v'}
+//
+//      Δ = -k(v), +k(v), ...
+//
+// => for all buckets
+//
+//      Δ accumulates to []δk(v)[n+,n-]  n+ ∈ {0,1}, n- ∈ {0,1}, if n+=n- - cancel
+//
+//
+// BTree:
+//
+//      old = {k  -> B}   or {k  -> T}
+//      new = {k' -> B'}  or {k' -> T'}
+//
+//      Δ = -k(B), +k(B), -k(T), +K(T), ...
+//
+// we translate (in top-down order):
+//
+//      k(B) -> {} of k(v)
+//      k(T) -> {} of k(B) -> {} of k(v)
+//
+// which gives
+//
+//      Δ = k(v), +k(v), ...
+//
+// i.e. exactly as for buckets and it accumulates to global Δ.
+//
+// The globally-accumulated Δ is the answer for δ(BTree, (@new, []oid))
+//
+// top-down order is obtained via toposort({oid}) wrt visited PathSet.
+//
+// δ(BTree) in wcfs context:
+//
+// . -k(blk) -> invalidate #blk
+// . +k(blk) -> invalidate #blk (e.g. if blk was previously read as hole)
+
 //go:generate ../../gen-set δbtree Tree *Tree zset_tree.go
 //go:generate ../../gen-set δbtree Object interface{} zset_object.go
 
@@ -110,7 +157,9 @@ func (δb *ΔTail) Track(path []Node) {	// XXX Tree|Bucket; path[0] = root
 /*
 	root = path[0]
 	for obj in path:
-		.rootIdx[obj] += root
+		if not obj in trackIdx:
+			.new += obj		# XXX .4rebuild += ... ?
+		.trackIdx[obj] += root
 */
 }
 
@@ -140,14 +189,14 @@ func (δB *ΔTail) Update(δZ *zodb.EventCommit) {
 	for root, δZ in δbZ:
 		toposort(δZ)
 		for δ in δZ:
-			T  | B  = zconn.Get(δ)		// XXX .zconn must be at .head and active
+			T  | B  = zconnOld.Get(δ)	// XXX .zconnOld must be at .head and active
 			T' | B' = zconnNew.Get(δ)
 			diff(T, T')
 			diff(B, B')
 			...
 
 
-	.tailv <- [] of (root, []key)
+	.δBtail <- [] of (root, []key)
 */
 }
 

wcfs/notes.txt

@@ -182,53 +182,3 @@ Lock request has been issued. Thus the following scenario is possible::
 
 To avoid such deadlocks zwatcher asks OS cache uploaders to pause while it is
 running, and retries taking zconnMu.Lock until all uploaders are indeed paused.
-
-
-δ(BTree) notes (XXX -> btreediff package)
-=========================================
-
-input: BTree, (@new, []oid)  ->  find out δ(BTree) i.e. {-k(v), +k'(v'), ...}
-
-- oid ∈ Bucket
-- oid ∈ BTree
-
-Bucket:
-
-     old = {k  -> v}
-     new = {k' -> v'}
-
-     Δ = -k(v), +k(v), ...
-
-=> for all buckets
-
-     Δ accumulates to []δk(v)[n+,n-]  n+ ∈ {0,1}, n- ∈ {0,1}, if n+=n- - cancel
-
-
-BTree:
-
-     old = {k  -> B}   or {k  -> T}
-     new = {k' -> B'}  or {k' -> T'}
-
-     Δ = -k(B), +k(B), -k(T), +K(T), ...
-
-we translate (in top-down order):
-
-     k(B) -> {} of k(v)
-     k(T) -> {} of k(B) -> {} of k(v)
-
-which gives
-
-     Δ = k(v), +k(v), ...
-
-i.e. exactly as for buckets and it accumulates to global Δ.
-
-The globally-accumulated Δ is the answer for δ(BTree, (@new, []oid))
-
-top-down order is obtained via toposort({oid}) wrt visited PathSet.
-
-XXX -> internal/btreediff ?
-
-δ(BTree) in wcfs context:
-
-. -k(blk) -> invalidate #blk
-. +k(blk) -> invalidate #blk (e.g. if blk was previously read as hole)