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feat(lib/trie): only copy nodes when mutation is certain (#2352)
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- Only copy nodes when mutation is certain
- Should alleviate memory operations and garbage collection load
- Trie snapshot helper methods `prepLeafForMutation` and `prepBranchForMutation`
- Call `SetDirty(true)` in snapshot trie helper methods
- Add test case to reach back full coverage of trie.go
- Note there is still full unit test coverage (from `trie_test.go`) making these changes possible/safe.
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@qdm12
qdm12 committed Mar 16, 2022
1 parent 846bb47 commit 86624cf
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Showing 2 changed files with 94 additions and 125 deletions.
181 changes: 72 additions & 109 deletions lib/trie/trie.go
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Original file line number Diff line number Diff line change
Expand Up @@ -62,17 +62,37 @@ func (t *Trie) Snapshot() (newTrie *Trie) {
}
}

func (t *Trie) prepLeafForMutation(currentLeaf *node.Leaf) (newLeaf *node.Leaf) {
if currentLeaf.Generation == t.generation {
// no need to deep copy and update generation
// of current leaf.
newLeaf = currentLeaf
} else {
newNode := updateGeneration(currentLeaf, t.generation, t.deletedKeys)
newLeaf = newNode.(*node.Leaf)
}
newLeaf.SetDirty(true)
return newLeaf
}

func (t *Trie) prepBranchForMutation(currentBranch *node.Branch) (newBranch *node.Branch) {
if currentBranch.Generation == t.generation {
// no need to deep copy and update generation
// of current branch.
newBranch = currentBranch
} else {
newNode := updateGeneration(currentBranch, t.generation, t.deletedKeys)
newBranch = newNode.(*node.Branch)
}
newBranch.SetDirty(true)
return newBranch
}

// updateGeneration is called when the currentNode is from
// an older trie generation (snapshot) so we deep copy the
// node and update the generation on the newer copy.
func updateGeneration(currentNode Node, trieGeneration uint64,
deletedHashes map[common.Hash]struct{}) (newNode Node) {
if currentNode.GetGeneration() == trieGeneration {
panic(fmt.Sprintf(
"current node has the same generation %d as the trie generation, "+
"make sure the caller properly checks for the node generation to "+
"be smaller than the trie generation.", trieGeneration))
}
const copyChildren = false
newNode = currentNode.Copy(copyChildren)
newNode.SetGeneration(trieGeneration)
Expand Down Expand Up @@ -322,29 +342,26 @@ func (t *Trie) insert(parent Node, key, value []byte) (newParent Node) {
}

// TODO ensure all values have dirty set to true
newParent = parent
if parent.GetGeneration() < t.generation {
newParent = updateGeneration(parent, t.generation, t.deletedKeys)
}

switch newParent.Type() {
switch parent.Type() {
case node.BranchType, node.BranchWithValueType:
parentBranch := newParent.(*node.Branch)
parentBranch := parent.(*node.Branch)
return t.insertInBranch(parentBranch, key, value)
default:
parentLeaf := newParent.(*node.Leaf)
parentLeaf := parent.(*node.Leaf)
return t.insertInLeaf(parentLeaf, key, value)
}
}

func (t *Trie) insertInLeaf(parentLeaf *node.Leaf, key,
value []byte) (newParent Node) {
if bytes.Equal(parentLeaf.Key, key) {
if !bytes.Equal(value, parentLeaf.Value) {
parentLeaf.Value = value
parentLeaf.Generation = t.generation
parentLeaf.SetDirty(true)
if bytes.Equal(value, parentLeaf.Value) {
return parentLeaf
}

parentLeaf = t.prepLeafForMutation(parentLeaf)
parentLeaf.Value = value
return parentLeaf
}

Expand All @@ -364,9 +381,9 @@ func (t *Trie) insertInLeaf(parentLeaf *node.Leaf, key,

if len(key) < len(parentLeafKey) {
// Move the current leaf parent as a child to the new branch.
parentLeaf = t.prepLeafForMutation(parentLeaf)
childIndex := parentLeafKey[commonPrefixLength]
parentLeaf.Key = parentLeaf.Key[commonPrefixLength+1:]
parentLeaf.SetDirty(true)
newBranchParent.Children[childIndex] = parentLeaf
}

Expand All @@ -378,9 +395,9 @@ func (t *Trie) insertInLeaf(parentLeaf *node.Leaf, key,
newBranchParent.Value = parentLeaf.Value
} else {
// make the leaf a child of the new branch
parentLeaf = t.prepLeafForMutation(parentLeaf)
childIndex := parentLeafKey[commonPrefixLength]
parentLeaf.Key = parentLeaf.Key[commonPrefixLength+1:]
parentLeaf.SetDirty(true)
newBranchParent.Children[childIndex] = parentLeaf
}
childIndex := key[commonPrefixLength]
Expand All @@ -395,9 +412,9 @@ func (t *Trie) insertInLeaf(parentLeaf *node.Leaf, key,
}

func (t *Trie) insertInBranch(parentBranch *node.Branch, key, value []byte) (newParent Node) {
parentBranch = t.prepBranchForMutation(parentBranch)

if bytes.Equal(key, parentBranch.Key) {
parentBranch.SetDirty(true)
parentBranch.Generation = t.generation
parentBranch.Value = value
return parentBranch
}
Expand All @@ -418,12 +435,9 @@ func (t *Trie) insertInBranch(parentBranch *node.Branch, key, value []byte) (new
}
} else {
child = t.insert(child, remainingKey, value)
child.SetDirty(true)
}

parentBranch.Children[childIndex] = child
parentBranch.SetDirty(true)
parentBranch.Generation = t.generation
return parentBranch
}

Expand All @@ -435,13 +449,11 @@ func (t *Trie) insertInBranch(parentBranch *node.Branch, key, value []byte) (new
Generation: t.generation,
Dirty: true,
}
parentBranch.SetDirty(true)

oldParentIndex := parentBranch.Key[commonPrefixLength]
remainingOldParentKey := parentBranch.Key[commonPrefixLength+1:]

parentBranch.Key = remainingOldParentKey
parentBranch.Generation = t.generation
newParentBranch.Children[oldParentIndex] = parentBranch

if len(key) <= commonPrefixLength {
Expand Down Expand Up @@ -653,36 +665,20 @@ func (t *Trie) clearPrefixLimit(parent Node, prefix []byte, limit uint32) (
return nil, 0, true
}

newParent = parent
if parent.GetGeneration() < t.generation {
newParent = updateGeneration(parent, t.generation, t.deletedKeys)
}

if newParent.Type() == node.LeafType {
leaf := newParent.(*node.Leaf)
if parent.Type() == node.LeafType {
leaf := parent.(*node.Leaf)
// if prefix is not found, it's also all deleted.
// TODO check this is the same behaviour as in substrate
const allDeleted = true
if bytes.HasPrefix(leaf.Key, prefix) {
valuesDeleted = 1
return nil, valuesDeleted, allDeleted
}
// not modified so return the leaf of the original
// trie generation. The copied leaf newParent will be
// garbage collected.
return parent, 0, allDeleted
}

branch := newParent.(*node.Branch)
newParent, valuesDeleted, allDeleted = t.clearPrefixLimitBranch(branch, prefix, limit)
if valuesDeleted == 0 {
// not modified so return the node of the original
// trie generation. The copied newParent will be
// garbage collected.
newParent = parent
}

return newParent, valuesDeleted, allDeleted
branch := parent.(*node.Branch)
return t.clearPrefixLimitBranch(branch, prefix, limit)
}

func (t *Trie) clearPrefixLimitBranch(branch *node.Branch, prefix []byte, limit uint32) (
Expand Down Expand Up @@ -714,13 +710,14 @@ func (t *Trie) clearPrefixLimitBranch(branch *node.Branch, prefix []byte, limit
childPrefix := prefix[len(branch.Key)+1:]
child := branch.Children[childIndex]

newParent = branch // mostly just a reminder for the reader
branch.Children[childIndex], valuesDeleted, allDeleted = t.clearPrefixLimit(child, childPrefix, limit)
if valuesDeleted > 0 {
branch.SetDirty(true)
newParent = handleDeletion(branch, prefix)
child, valuesDeleted, allDeleted = t.clearPrefixLimit(child, childPrefix, limit)
if valuesDeleted == 0 {
return branch, valuesDeleted, allDeleted
}

branch = t.prepBranchForMutation(branch)
branch.Children[childIndex] = child
newParent = handleDeletion(branch, prefix)
return newParent, valuesDeleted, allDeleted
}

Expand All @@ -738,11 +735,16 @@ func (t *Trie) clearPrefixLimitChild(branch *node.Branch, prefix []byte, limit u
}

nilPrefix := ([]byte)(nil)
branch.Children[childIndex], valuesDeleted = t.deleteNodesLimit(child, nilPrefix, limit)
branch.SetDirty(true)
child, valuesDeleted = t.deleteNodesLimit(child, nilPrefix, limit)
if valuesDeleted == 0 {
allDeleted = branch.Children[childIndex] == nil
return branch, valuesDeleted, allDeleted
}

newParent = handleDeletion(branch, prefix)
branch = t.prepBranchForMutation(branch)
branch.Children[childIndex] = child

newParent = handleDeletion(branch, prefix)
allDeleted = branch.Children[childIndex] == nil
return newParent, valuesDeleted, allDeleted
}
Expand All @@ -757,17 +759,12 @@ func (t *Trie) deleteNodesLimit(parent Node, prefix []byte, limit uint32) (
return nil, 0
}

newParent = parent
if parent.GetGeneration() < t.generation {
newParent = updateGeneration(parent, t.generation, t.deletedKeys)
}

if newParent.Type() == node.LeafType {
if parent.Type() == node.LeafType {
valuesDeleted = 1
return nil, valuesDeleted
}

branch := newParent.(*node.Branch)
branch := parent.(*node.Branch)

fullKey := concatenateSlices(prefix, branch.Key)

Expand All @@ -779,14 +776,14 @@ func (t *Trie) deleteNodesLimit(parent Node, prefix []byte, limit uint32) (
continue
}

branch = t.prepBranchForMutation(branch)
branch.Children[i], newDeleted = t.deleteNodesLimit(child, fullKey, limit)
if branch.Children[i] == nil {
nilChildren++
}
limit -= newDeleted
valuesDeleted += newDeleted

branch.SetDirty(true)
newParent = handleDeletion(branch, fullKey)
if nilChildren == node.ChildrenCapacity &&
branch.Value == nil {
Expand Down Expand Up @@ -825,23 +822,15 @@ func (t *Trie) clearPrefix(parent Node, prefix []byte) (
return nil, false
}

newParent = parent
if parent.GetGeneration() < t.generation {
newParent = updateGeneration(parent, t.generation, t.deletedKeys)
}

if bytes.HasPrefix(newParent.GetKey(), prefix) {
if bytes.HasPrefix(parent.GetKey(), prefix) {
return nil, true
}

if newParent.Type() == node.LeafType {
// not modified so return the leaf of the original
// trie generation. The copied newParent will be
// garbage collected.
if parent.Type() == node.LeafType {
return parent, false
}

branch := newParent.(*node.Branch)
branch := parent.(*node.Branch)

if len(prefix) == len(branch.Key)+1 &&
bytes.HasPrefix(branch.Key, prefix[:len(prefix)-1]) {
Expand All @@ -850,41 +839,32 @@ func (t *Trie) clearPrefix(parent Node, prefix []byte) (
child := branch.Children[childIndex]

if child == nil {
// child is already nil at the child index
// node is not modified so return the branch of the original
// trie generation. The copied newParent will be
// garbage collected.
return parent, false
}

branch = t.prepBranchForMutation(branch)
branch.Children[childIndex] = nil
branch.SetDirty(true)
newParent = handleDeletion(branch, prefix)
return newParent, true
}

noPrefixForNode := len(prefix) <= len(branch.Key) ||
lenCommonPrefix(branch.Key, prefix) < len(branch.Key)
if noPrefixForNode {
// not modified so return the branch of the original
// trie generation. The copied newParent will be
// garbage collected.
return parent, false
}

childIndex := prefix[len(branch.Key)]
childPrefix := prefix[len(branch.Key)+1:]
child := branch.Children[childIndex]

branch.Children[childIndex], updated = t.clearPrefix(child, childPrefix)
child, updated = t.clearPrefix(child, childPrefix)
if !updated {
// branch not modified so return the branch of the original
// trie generation. The copied newParent will be
// garbage collected.
return parent, false
}

branch.SetDirty(true)
branch = t.prepBranchForMutation(branch)
branch.Children[childIndex] = child
newParent = handleDeletion(branch, prefix)
return newParent, true
}
Expand All @@ -902,32 +882,15 @@ func (t *Trie) delete(parent Node, key []byte) (newParent Node, deleted bool) {
return nil, false
}

newParent = parent
if parent.GetGeneration() < t.generation {
newParent = updateGeneration(parent, t.generation, t.deletedKeys)
}

if newParent.Type() == node.LeafType {
newParent = deleteLeaf(newParent, key)
if newParent == nil {
if parent.Type() == node.LeafType {
if deleteLeaf(parent, key) == nil {
return nil, true
}
// The leaf was not deleted so return the original
// parent without its generation updated.
// The copied newParent will be garbage collected.
return parent, false
}

branch := newParent.(*node.Branch)
newParent, deleted = t.deleteBranch(branch, key)
if !deleted {
// Nothing was deleted so return the original
// parent without its generation updated.
// The copied newParent will be garbage collected.
return parent, false
}

return newParent, true
branch := parent.(*node.Branch)
return t.deleteBranch(branch, key)
}

func deleteLeaf(parent Node, key []byte) (newParent Node) {
Expand All @@ -939,8 +902,8 @@ func deleteLeaf(parent Node, key []byte) (newParent Node) {

func (t *Trie) deleteBranch(branch *node.Branch, key []byte) (newParent Node, deleted bool) {
if len(key) == 0 || bytes.Equal(branch.Key, key) {
branch = t.prepBranchForMutation(branch)
branch.Value = nil
branch.SetDirty(true)
return handleDeletion(branch, key), true
}

Expand All @@ -954,8 +917,8 @@ func (t *Trie) deleteBranch(branch *node.Branch, key []byte) (newParent Node, de
return branch, false
}

branch = t.prepBranchForMutation(branch)
branch.Children[childIndex] = newChild
branch.SetDirty(true)
newParent = handleDeletion(branch, key)
return newParent, true
}
Expand Down
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