.

wcfs/internal/δbtree/δbtail.go → wcfs/internal/xbtree/δbtail.go

@@ -17,27 +17,39 @@
 // See COPYING file for full licensing terms.
 // See https://www.nexedi.com/licensing for rationale and options.
 
-package δbtree
-// XXX -> another package?
+// Package xbtree complements package lab.nexedi.com/kirr/neo/go/zodb/btree.
+//
+// TODO move -> btree when ΔTail matures.
+package xbtree
+
+//go:generate ../../gen-set δbtree Tree *Tree zset_tree.go
+//go:generate ../../gen-set δbtree Object interface{} zset_object.go
 
 import (
 	"lab.nexedi.com/kirr/neo/go/zodb"
+	"lab.nexedi.com/kirr/neo/go/zodb/btree"
 )
 
-// ΔBTail reprsents tail of revisional changes to BTrees.
+type Tree   = btree.LOBTree
+type Bucket = btree.LOBucket
+type Node   = btree.LONode
+type Key    = int64
+
+// ΔTail reprsents tail of revisional changes to BTrees.
 //
 // It semantically consists of
 //
-//	[](rev↑, (tree, []key))		; rev ∈ (tail, head]
+//	[](rev↑, [](tree, []key))	; rev ∈ (tail, head]
 //
-// and *partially* covers changes to BTrees.
+// and covers changes to tracked subsets of BTrees. A tree subset becomes
+// tracked via Track(path) request.
 //
 // XXX δB can convert δZ to btree changes, but only at least for δZ's objects
 // that ∈ BTree subgraphs that were explicitly requested to be tracked by δB.
 //
 // XXX incremental; not full coverage
-// XXX -> ΔBIndex ?
-type ΔBTail struct {
+// XXX concurency safety
+type ΔTail struct {
 	//at // = head
 	δZtail *zodb.ΔTail
 
@@ -49,10 +61,24 @@ type ΔBTail struct {
 	rootIdx map[zodb.Oid]SetTree // oid -> {} roots
 }
 
+// ΔRevEntry represents information about BTrees changes in one revision.
+type ΔRevEntry struct {
+	Rev     zodb.Tid
+	Changev []ΔTree
+}
+
+// ΔTree represents changes to one tree.
+type ΔTree struct {
+	Root XXX
+	Keyv []Key
+}
+
+// Track adds tree path to tracked set.
+//
 // XXX path is at @at state.
 // XXX objects in path must be with .PJar().At() == .head
 // XXX path -> []oid ?
-func (δb *ΔBTail) Track(path []zodb.IPersistent) {	// XXX Tree|Bucket; path[0] = root
+func (δb *ΔTail) Track(path []Node) {	// XXX Tree|Bucket; path[0] = root
 /*
 	root = path[0]
 	for obj in path:
@@ -62,12 +88,12 @@ func (δb *ΔBTail) Track(path []zodb.IPersistent) {	// XXX Tree|Bucket; path[0]
 
 // Update updates δB with per-object level ZODB changes.
 //
-// XXX return -> [] of (root, []key) that are invalidated.
+// Only those objects from δZ that belong to tracked set are guaranteed to be
+// taken into account.
 //
-// XXX text ...
-// XXX -> Append? -> Invalidate?
-// XXX -> DiffTo ?
-func (δB *ΔBTail) Update(δZ *zodb.EventCommit) {
+// XXX return -> [] of (root, []key) that are invalidated.
+// XXX -> + separate SliceByRev? or Data to get diff?
+func (δB *ΔTail) Update(δZ *zodb.EventCommit) {
 /*
 	.δZtail += δZ
 	δbZ = {}
@@ -91,17 +117,16 @@ func (δB *ΔBTail) Update(δZ *zodb.EventCommit) {
 			diff(B, B')
 			...
 
-			XXX rebuild something?
 
-	-> [] of (root, []key)
+	.tailv <- [] of (root, []key)
 */
 }
 
 // XXX -> Get(root, key, at) -> (valueOid, rev) ?
-func (δB *ΔBTail) LastRevOf(root Tree, key Key, at zodb.Tid) zodb.Tid {
+func (δB *ΔTail) LastRevOf(root Tree, key Key, at zodb.Tid) zodb.Tid {
 	panic("TODO") // XXX return 0 as stub?
 }
 
-func (δB *ΔBTail) ForgetPast(revCut zodb.Tid) {
+func (δB *ΔTail) ForgetPast(revCut zodb.Tid) {
 	panic("TODO")
 }

wcfs/wcfs.go

@@ -248,11 +248,15 @@ package main
 //	#blk ∈ OS file cache    =>    ZBlk(#blk) + all BTree/Bucket that lead to it  ∈ zhead cache(%)
 //	                              (ZBlk* in ghost state)
 //
+//	                        =>    all BTree/Bucket that lead to blk are tracked (XXX)
+//
 //    The invariant helps on invalidation: if we see a changed oid, and
 //    zhead.cache.lookup(oid) = ø -> we know we don't have to invalidate OS
 //    cache for any part of any file (even if oid relates to a file block - that
 //    block is not cached and will trigger ZODB load on file read).
 //
+//    XXX explain why tracked
+//
 //    Currently we maintain this invariant by simply never evicting ZBlk/LOBTree/LOBucket
 //    objects from ZODB Connection cache. In the future we may want to try to
 //    synchronize to kernel freeing its pagecache pages.