[#288] pilorama: Remove childMap from memory forest

Memory forest is here to check the correctness of boltdb optimized
implementation. Let's keep it simple.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/local_object_storage/pilorama/forest.go

@@ -153,11 +153,7 @@ func (f *memoryForest) TreeGetChildren(_ context.Context, cid cid.ID, treeID str
 		return nil, ErrTreeNotFound
 	}
 
-	children, ok := s.childMap[nodeID]
-	if !ok {
-		return nil, nil
-	}
-
+	children := s.tree.getChildren(nodeID)
 	res := make([]Node, len(children))
 	copy(res, children)
 	return res, nil

pkg/local_object_storage/pilorama/forest_test.go

@@ -714,13 +714,6 @@ func compareForests(t *testing.T, expected, actual Forest, cid cidSDK.ID, treeID
 				require.True(t, ok)
 				require.Equal(t, se.operations, sa.operations)
 				require.Equal(t, se.infoMap, sa.infoMap)
-
-				require.Equal(t, len(se.childMap), len(sa.childMap))
-				for ck, la := range sa.childMap {
-					le, ok := se.childMap[ck]
-					require.True(t, ok)
-					require.ElementsMatch(t, le, la)
-				}
 			}
 			require.Equal(t, expected, actual, i)
 		}

pkg/local_object_storage/pilorama/inmemory.go

@@ -1,5 +1,7 @@
 package pilorama
 
+import "sort"
+
 // nodeInfo couples parent and metadata.
 type nodeInfo struct {
 	Parent Node
@@ -27,27 +29,8 @@ func newState() *state {
 
 // undo un-does op and changes s in-place.
 func (s *state) undo(op *move) {
-	children := s.tree.childMap[op.Parent]
-	for i := range children {
-		if children[i] == op.Child {
-			if len(children) > 1 {
-				s.tree.childMap[op.Parent] = append(children[:i], children[i+1:]...)
-			} else {
-				delete(s.tree.childMap, op.Parent)
-			}
-			break
-		}
-	}
-
 	if op.HasOld {
 		s.tree.infoMap[op.Child] = op.Old
-		oldChildren := s.tree.childMap[op.Old.Parent]
-		for i := range oldChildren {
-			if oldChildren[i] == op.Child {
-				return
-			}
-		}
-		s.tree.childMap[op.Old.Parent] = append(oldChildren, op.Child)
 	} else {
 		delete(s.tree.infoMap, op.Child)
 	}
@@ -104,28 +87,15 @@ func (s *state) do(op *Move) move {
 
 	if !ok {
 		p.Meta.Time = op.Time
-	} else {
-		s.removeChild(op.Child, p.Parent)
 	}
 
 	p.Meta = op.Meta
 	p.Parent = op.Parent
 	s.tree.infoMap[op.Child] = p
-	s.tree.childMap[op.Parent] = append(s.tree.childMap[op.Parent], op.Child)
 
 	return lm
 }
 
-func (s *state) removeChild(child, parent Node) {
-	oldChildren := s.tree.childMap[parent]
-	for i := range oldChildren {
-		if oldChildren[i] == child {
-			s.tree.childMap[parent] = append(oldChildren[:i], oldChildren[i+1:]...)
-			break
-		}
-	}
-}
-
 func (s *state) timestamp(pos, size int) Timestamp {
 	if len(s.operations) == 0 {
 		return nextTimestamp(0, uint64(pos), uint64(size))
@@ -145,16 +115,30 @@ func (s *state) findSpareID() Node {
 type tree struct {
 	syncHeight uint64
 	infoMap    map[Node]nodeInfo
-	childMap   map[Node][]Node
 }
 
 func newTree() *tree {
 	return &tree{
-		childMap: make(map[Node][]Node),
-		infoMap:  make(map[Node]nodeInfo),
+		infoMap: make(map[Node]nodeInfo),
 	}
 }
 
+func (t tree) getChildren(parent Node) []Node {
+	var children []Node
+	for c, info := range t.infoMap {
+		if info.Parent == parent {
+			children = append(children, c)
+		}
+	}
+
+	sort.Slice(children, func(i, j int) bool {
+		a := t.infoMap[children[i]]
+		b := t.infoMap[children[j]]
+		return a.Meta.Time < b.Meta.Time
+	})
+	return children
+}
+
 // isAncestor returns true if parent is an ancestor of a child.
 // For convenience, also return true if parent == child.
 func (t tree) isAncestor(parent, child Node) bool {
@@ -176,7 +160,7 @@ func (t tree) getPathPrefix(attr string, path []string) (int, Node) {
 
 loop:
 	for i := range path {
-		children := t.childMap[curNode]
+		children := t.getChildren(curNode)
 		for j := range children {
 			meta := t.infoMap[children[j]].Meta
 			f := meta.GetAttr(attr)
@@ -206,7 +190,7 @@ func (t tree) get(attr string, path []string, latest bool) []Node {
 	var nodes []Node
 	var lastTs Timestamp
 
-	children := t.childMap[curNode]
+	children := t.getChildren(curNode)
 	for i := range children {
 		info := t.infoMap[children[i]]
 		fileName := string(info.Meta.GetAttr(attr))