.

wcfs/internal/xbtree/δbtail.go

@@ -93,7 +93,8 @@ type ΔBtail struct {
 	// includes all changed objects, not only tracked ones.
 	δZtail *zodb.ΔTail
 
-	byRoot map[zodb.Oid]*ΔTtail // {} root -> [] k/v change history; only for keys ∈ tracked subset
+	vδBroots []ΔBroots            // [] (rev, roots changed in this rev)
+	byRoot   map[zodb.Oid]*ΔTtail // {} root -> [] k/v change history; only for keys ∈ tracked subset	XXX -> vδByRoot ?
 
 	// handle to make connections to access database.
 	// TODO allow client to optionally provide zconnOld/zconnNew on e.g. Update()
@@ -127,11 +128,18 @@ type ΔTtail struct {
 	lastRevOf map[Key]zodb.Tid // {} key -> last
 }
 
+// ΔBroots represents roots-only part of ΔB - a change in BTrees space.
+//
+// It describes which trees were changed, but does not provide δkv details for changed trees.
+type ΔBroots struct {
+	Rev    zodb.Tid
+	ΔRoots SetOid   // which roots changed in this revision
+}
 
 // ΔB represents a change in BTrees space.
 type ΔB struct {
 	Rev    zodb.Tid
-	ByRoot map[zodb.Oid]map[Key]ΔValue // {} root -> {}(key, δvalue)
+	ByRoot map[zodb.Oid]map[Key]ΔValue // {} root -> {}(key, δvalue)	XXX -> ΔByRoot ?
 }
 
 // ΔTree describes changes to one BTree in one revision.
@@ -207,7 +215,12 @@ func (δBtail *ΔBtail) Head() zodb.Tid { return δBtail.δZtail.Head() }
 func (δBtail *ΔBtail) Tail() zodb.Tid { return δBtail.δZtail.Tail() }
 
 // XXX SliceByRev?
-// XXX ForgetPast
+
+// ForgetPast XXX
+func (δBtail *ΔBtail) ForgetPast(revCut zodb.Tid) {
+	// TODO go throough vδBroots till revcut -> find which trees to trim -> trim ΔTtails.
+	panic("TODO")
+}
 
 // Track adds tree path to tracked set.
 //