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Fix miscalculation of tree size in concurrent editing (#891)
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This commit addresses the issue where the updateAncestorsSize method
subtracts the size of a tombstoned node from its ancestors' sizes when
the node is removed. However, the previous logic did not consider
cases where ancestors node are tombstoned. In such cases, the update
should not propagate to the parent's ancestors. This commit introduces
recursive checks on ancestors and stops updating process if a
tombstoned ancestor is encountered.

Furthermore, the PR ensures consistency between the size maintenance
policies of updateDescendantsSize and updateAncestorsSize.

---------

Co-authored-by: Youngteac Hong <[email protected]>
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@raararaara @hackerwins
raararaara and hackerwins authored Jun 7, 2024
1 parent ef70028 commit 12f7baa
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Showing 3 changed files with 148 additions and 13 deletions.
6 changes: 1 addition & 5 deletions pkg/document/crdt/tree.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -373,11 +373,7 @@ func (n *TreeNode) remove(removedAt *time.Ticket) bool {
if n.removedAt == nil || n.removedAt.Compare(removedAt) > 0 {
n.removedAt = removedAt
if justRemoved {
if n.Index.Parent.Value.removedAt == nil {
n.Index.UpdateAncestorsSize()
} else {
n.Index.Parent.Length -= n.Index.PaddedLength()
}
n.Index.UpdateAncestorsSize()
}
return justRemoved
}
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19 changes: 11 additions & 8 deletions pkg/index/tree.go
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Original file line number Diff line number Diff line change
Expand Up @@ -336,6 +336,9 @@ func (n *Node[V]) UpdateAncestorsSize() {

for parent != nil {
parent.Length += n.PaddedLength() * sign
if parent.Value.IsRemoved() {
break
}

parent = parent.Parent
}
Expand All @@ -344,17 +347,17 @@ func (n *Node[V]) UpdateAncestorsSize() {
// UpdateDescendantsSize updates the size of descendants. It is used when
// the tree is newly created and the size of the descendants is not calculated.
func (n *Node[V]) UpdateDescendantsSize() int {
if n.Value.IsRemoved() {
n.Length = 0
return 0
}

sum := 0
size := 0
for _, child := range n.Children(true) {
sum += child.UpdateDescendantsSize()
childSize := child.UpdateDescendantsSize()
if child.Value.IsRemoved() {
continue
}

size += childSize
}

n.Length += sum
n.Length += size

return n.PaddedLength()
}
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136 changes: 136 additions & 0 deletions test/integration/tree_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,9 @@ import (

"github.com/stretchr/testify/assert"

"github.com/yorkie-team/yorkie/api/converter"
"github.com/yorkie-team/yorkie/pkg/document"
"github.com/yorkie-team/yorkie/pkg/document/crdt"
"github.com/yorkie-team/yorkie/pkg/document/json"
"github.com/yorkie-team/yorkie/pkg/document/presence"
"github.com/yorkie-team/yorkie/pkg/index"
Expand Down Expand Up @@ -3501,6 +3503,140 @@ func TestTree(t *testing.T) {
assert.Equal(t, size, d2.Root().GetTree("t").IndexTree.Root().Len())
})

t.Run("can calculate size of index tree correctly during concurrent editing", func(t *testing.T) {
ctx := context.Background()
d1 := document.New(helper.TestDocKey(t))
assert.NoError(t, c1.Attach(ctx, d1))
d2 := document.New(helper.TestDocKey(t))
assert.NoError(t, c2.Attach(ctx, d2))

assert.NoError(t, d1.Update(func(root *json.Object, p *presence.Presence) error {
root.SetNewTree("t", &json.TreeNode{
Type: "doc",
Children: []json.TreeNode{{
Type: "p",
Children: []json.TreeNode{{Type: "text", Value: "hello"}},
}},
})
return nil
}))
assert.NoError(t, c1.Sync(ctx))
assert.NoError(t, c2.Sync(ctx))

assert.Equal(t, "<doc><p>hello</p></doc>", d1.Root().GetTree("t").ToXML())
assert.Equal(t, "<doc><p>hello</p></doc>", d2.Root().GetTree("t").ToXML())

assert.NoError(t, d1.Update(func(root *json.Object, p *presence.Presence) error {
root.GetTree("t").Edit(0, 7, nil, 0)
return nil
}))
assert.NoError(t, d2.Update(func(root *json.Object, p *presence.Presence) error {
root.GetTree("t").Edit(1, 2, &json.TreeNode{
Type: "text",
Value: "p",
}, 0)
return nil
}))
assert.Equal(t, "<doc></doc>", d1.Root().GetTree("t").ToXML())
assert.Equal(t, 0, d1.Root().GetTree("t").Len())
assert.Equal(t, "<doc><p>pello</p></doc>", d2.Root().GetTree("t").ToXML())
assert.Equal(t, 7, d2.Root().GetTree("t").Len())
assert.NoError(t, c1.Sync(ctx))
assert.NoError(t, c2.Sync(ctx))
assert.NoError(t, c1.Sync(ctx))

assert.Equal(t, "<doc></doc>", d1.Root().GetTree("t").ToXML())
assert.Equal(t, "<doc></doc>", d2.Root().GetTree("t").ToXML())
assert.Equal(t, d1.Root().GetTree("t").Len(), d2.Root().GetTree("t").Len())
})

t.Run("can keep index tree consistent from snapshot", func(t *testing.T) {
ctx := context.Background()
d1 := document.New(helper.TestDocKey(t))
assert.NoError(t, c1.Attach(ctx, d1))
d2 := document.New(helper.TestDocKey(t))
assert.NoError(t, c2.Attach(ctx, d2))

assert.NoError(t, d1.Update(func(root *json.Object, p *presence.Presence) error {
root.SetNewTree("t", &json.TreeNode{
Type: "r",
Children: []json.TreeNode{{
Type: "p",
Children: []json.TreeNode{},
}},
})
return nil
}))
assert.NoError(t, c1.Sync(ctx))
assert.NoError(t, c2.Sync(ctx))

assert.Equal(t, "<r><p></p></r>", d1.Root().GetTree("t").ToXML())
assert.Equal(t, "<r><p></p></r>", d2.Root().GetTree("t").ToXML())

assert.NoError(t, d1.Update(func(root *json.Object, p *presence.Presence) error {
root.GetTree("t").Edit(0, 2, nil, 0)
return nil
}))
assert.NoError(t, d2.Update(func(root *json.Object, p *presence.Presence) error {
root.GetTree("t").Edit(1, 1, &json.TreeNode{
Type: "i",
Children: []json.TreeNode{{Type: "text", Value: "a"}},
}, 0)
root.GetTree("t").Edit(2, 3, &json.TreeNode{
Type: "text",
Value: "b",
}, 0)
return nil
}))
assert.Equal(t, "<r></r>", d1.Root().GetTree("t").ToXML())
assert.Equal(t, 0, d1.Root().GetTree("t").Len())
assert.Equal(t, "<r><p><i>b</i></p></r>", d2.Root().GetTree("t").ToXML())
assert.Equal(t, 5, d2.Root().GetTree("t").Len())
assert.NoError(t, c1.Sync(ctx))
assert.NoError(t, c2.Sync(ctx))
assert.NoError(t, c1.Sync(ctx))

assert.Equal(t, "<r></r>", d1.Root().GetTree("t").ToXML())
assert.Equal(t, "<r></r>", d2.Root().GetTree("t").ToXML())

type Node struct {
xml string
len int
isRemoved bool
}
var d1Nodes []Node
var d2Nodes []Node
var sNodes []Node

index.TraverseNode(d1.Root().GetTree("t").IndexTree.Root(), func(node *index.Node[*crdt.TreeNode], depth int) {
d1Nodes = append(d1Nodes, Node{
xml: index.ToXML(node),
len: node.Len(),
isRemoved: node.Value.IsRemoved(),
})
})
index.TraverseNode(d2.Root().GetTree("t").IndexTree.Root(), func(node *index.Node[*crdt.TreeNode], depth int) {
d2Nodes = append(d2Nodes, Node{
xml: index.ToXML(node),
len: node.Len(),
isRemoved: node.Value.IsRemoved(),
})
})
obj, err := converter.ObjectToBytes(d1.RootObject())
assert.NoError(t, err)
sRoot, err := converter.BytesToObject(obj)
assert.NoError(t, err)
index.TraverseNode(sRoot.Get("t").(*crdt.Tree).IndexTree.Root(), func(node *index.Node[*crdt.TreeNode], depth int) {
sNodes = append(sNodes, Node{
xml: index.ToXML(node),
len: node.Len(),
isRemoved: node.Value.IsRemoved(),
})
})
assert.ObjectsAreEqual(d1Nodes, d2Nodes)
assert.ObjectsAreEqual(d1Nodes, sNodes)
})

t.Run("can split and merge with empty paragraph: left", func(t *testing.T) {
ctx := context.Background()
d1 := document.New(helper.TestDocKey(t))
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