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trie: more node iterator improvements (#14615)

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* ethdb: remove Set

Set deadlocks immediately and isn't part of the Database interface.

* trie: add Err to Iterator

This is useful for testing because the underlying NodeIterator doesn't
need to be kept in a separate variable just to get the error.

* trie: add LeafKey to iterator, panic when not at leaf

LeafKey is useful for callers that can't interpret Path.

* trie: retry failed seek/peek in iterator Next

Instead of failing iteration irrecoverably, make it so Next retries the
pending seek or peek every time.

Smaller changes in this commit make this easier to test:

* The iterator previously returned from Next on encountering a hash
  node. This caused it to visit the same path twice.
* Path returned nibbles with terminator symbol for valueNode attached
  to fullNode, but removed it for valueNode attached to shortNode. Now
  the terminator is always present. This makes Path unique to each node
  and simplifies Leaf.

* trie: add Path to MissingNodeError

The light client trie iterator needs to know the path of the node that's
missing so it can retrieve a proof for it. NodeIterator.Path is not
sufficient because it is updated when the node is resolved and actually
visited by the iterator.

Also remove unused fields. They were added a long time ago before we
knew which fields would be needed for the light client.
This commit is contained in:
Felix Lange
2017-06-20 18:26:09 +02:00
committed by GitHub
parent 431cf2a1e4
commit 693d9ccbfb
7 changed files with 296 additions and 180 deletions
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259
trie/iterator.go
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@ -24,14 +24,13 @@ import (
"github.com/ethereum/go-ethereum/common"
)
var iteratorEnd = errors.New("end of iteration")
// Iterator is a key-value trie iterator that traverses a Trie.
type Iterator struct {
nodeIt NodeIterator
Key []byte // Current data key on which the iterator is positioned on
Value []byte // Current data value on which the iterator is positioned on
Err error
}
// NewIterator creates a new key-value iterator from a node iterator
@ -45,35 +44,42 @@ func NewIterator(it NodeIterator) *Iterator {
func (it *Iterator) Next() bool {
for it.nodeIt.Next(true) {
if it.nodeIt.Leaf() {
it.Key = hexToKeybytes(it.nodeIt.Path())
it.Key = it.nodeIt.LeafKey()
it.Value = it.nodeIt.LeafBlob()
return true
}
}
it.Key = nil
it.Value = nil
it.Err = it.nodeIt.Error()
return false
}
// NodeIterator is an iterator to traverse the trie pre-order.
type NodeIterator interface {
// Hash returns the hash of the current node
Hash() common.Hash
// Parent returns the hash of the parent of the current node
Parent() common.Hash
// Leaf returns true iff the current node is a leaf node.
Leaf() bool
// LeafBlob returns the contents of the node, if it is a leaf.
// Callers must not retain references to the return value after calling Next()
LeafBlob() []byte
// Path returns the hex-encoded path to the current node.
// Callers must not retain references to the return value after calling Next()
Path() []byte
// Next moves the iterator to the next node. If the parameter is false, any child
// nodes will be skipped.
Next(bool) bool
// Error returns the error status of the iterator.
Error() error
// Hash returns the hash of the current node.
Hash() common.Hash
// Parent returns the hash of the parent of the current node. The hash may be the one
// grandparent if the immediate parent is an internal node with no hash.
Parent() common.Hash
// Path returns the hex-encoded path to the current node.
// Callers must not retain references to the return value after calling Next.
// For leaf nodes, the last element of the path is the 'terminator symbol' 0x10.
Path() []byte
// Leaf returns true iff the current node is a leaf node.
// LeafBlob, LeafKey return the contents and key of the leaf node. These
// method panic if the iterator is not positioned at a leaf.
// Callers must not retain references to their return value after calling Next
Leaf() bool
LeafBlob() []byte
LeafKey() []byte
}
// nodeIteratorState represents the iteration state at one particular node of the
@ -89,8 +95,21 @@ type nodeIteratorState struct {
type nodeIterator struct {
trie *Trie // Trie being iterated
stack []*nodeIteratorState // Hierarchy of trie nodes persisting the iteration state
err error // Failure set in case of an internal error in the iterator
path []byte // Path to the current node
err error // Failure set in case of an internal error in the iterator
}
// iteratorEnd is stored in nodeIterator.err when iteration is done.
var iteratorEnd = errors.New("end of iteration")
// seekError is stored in nodeIterator.err if the initial seek has failed.
type seekError struct {
key []byte
err error
}
func (e seekError) Error() string {
return "seek error: " + e.err.Error()
}
func newNodeIterator(trie *Trie, start []byte) NodeIterator {
@ -98,60 +117,57 @@ func newNodeIterator(trie *Trie, start []byte) NodeIterator {
return new(nodeIterator)
}
it := &nodeIterator{trie: trie}
it.seek(start)
it.err = it.seek(start)
return it
}
// Hash returns the hash of the current node
func (it *nodeIterator) Hash() common.Hash {
if len(it.stack) == 0 {
return common.Hash{}
}
return it.stack[len(it.stack)-1].hash
}
// Parent returns the hash of the parent node
func (it *nodeIterator) Parent() common.Hash {
if len(it.stack) == 0 {
return common.Hash{}
}
return it.stack[len(it.stack)-1].parent
}
// Leaf returns true if the current node is a leaf
func (it *nodeIterator) Leaf() bool {
if len(it.stack) == 0 {
return false
}
_, ok := it.stack[len(it.stack)-1].node.(valueNode)
return ok
return hasTerm(it.path)
}
// LeafBlob returns the data for the current node, if it is a leaf
func (it *nodeIterator) LeafBlob() []byte {
if len(it.stack) == 0 {
return nil
if len(it.stack) > 0 {
if node, ok := it.stack[len(it.stack)-1].node.(valueNode); ok {
return []byte(node)
}
}
if node, ok := it.stack[len(it.stack)-1].node.(valueNode); ok {
return []byte(node)
}
return nil
panic("not at leaf")
}
func (it *nodeIterator) LeafKey() []byte {
if len(it.stack) > 0 {
if _, ok := it.stack[len(it.stack)-1].node.(valueNode); ok {
return hexToKeybytes(it.path)
}
}
panic("not at leaf")
}
// Path returns the hex-encoded path to the current node
func (it *nodeIterator) Path() []byte {
return it.path
}
// Error returns the error set in case of an internal error in the iterator
func (it *nodeIterator) Error() error {
if it.err == iteratorEnd {
return nil
}
if seek, ok := it.err.(seekError); ok {
return seek.err
}
return it.err
}
@ -160,29 +176,37 @@ func (it *nodeIterator) Error() error {
// sets the Error field to the encountered failure. If `descend` is false,
// skips iterating over any subnodes of the current node.
func (it *nodeIterator) Next(descend bool) bool {
if it.err != nil {
if it.err == iteratorEnd {
return false
}
// Otherwise step forward with the iterator and report any errors
if seek, ok := it.err.(seekError); ok {
if it.err = it.seek(seek.key); it.err != nil {
return false
}
}
// Otherwise step forward with the iterator and report any errors.
state, parentIndex, path, err := it.peek(descend)
if err != nil {
it.err = err
it.err = err
if it.err != nil {
return false
}
it.push(state, parentIndex, path)
return true
}
func (it *nodeIterator) seek(prefix []byte) {
func (it *nodeIterator) seek(prefix []byte) error {
// The path we're looking for is the hex encoded key without terminator.
key := keybytesToHex(prefix)
key = key[:len(key)-1]
// Move forward until we're just before the closest match to key.
for {
state, parentIndex, path, err := it.peek(bytes.HasPrefix(key, it.path))
if err != nil || bytes.Compare(path, key) >= 0 {
it.err = err
return
if err == iteratorEnd {
return iteratorEnd
} else if err != nil {
return seekError{prefix, err}
} else if bytes.Compare(path, key) >= 0 {
return nil
}
it.push(state, parentIndex, path)
}
@ -197,7 +221,8 @@ func (it *nodeIterator) peek(descend bool) (*nodeIteratorState, *int, []byte, er
if root != emptyRoot {
state.hash = root
}
return state, nil, nil, nil
err := state.resolve(it.trie, nil)
return state, nil, nil, err
}
if !descend {
// If we're skipping children, pop the current node first
@ -205,72 +230,73 @@ func (it *nodeIterator) peek(descend bool) (*nodeIteratorState, *int, []byte, er
}
// Continue iteration to the next child
for {
if len(it.stack) == 0 {
return nil, nil, nil, iteratorEnd
}
for len(it.stack) > 0 {
parent := it.stack[len(it.stack)-1]
ancestor := parent.hash
if (ancestor == common.Hash{}) {
ancestor = parent.parent
}
if node, ok := parent.node.(*fullNode); ok {
// Full node, move to the first non-nil child.
for i := parent.index + 1; i < len(node.Children); i++ {
child := node.Children[i]
if child != nil {
hash, _ := child.cache()
state := &nodeIteratorState{
hash: common.BytesToHash(hash),
node: child,
parent: ancestor,
index: -1,
pathlen: len(it.path),
}
path := append(it.path, byte(i))
parent.index = i - 1
return state, &parent.index, path, nil
}
}
} else if node, ok := parent.node.(*shortNode); ok {
// Short node, return the pointer singleton child
if parent.index < 0 {
hash, _ := node.Val.cache()
state := &nodeIteratorState{
hash: common.BytesToHash(hash),
node: node.Val,
parent: ancestor,
index: -1,
pathlen: len(it.path),
}
var path []byte
if hasTerm(node.Key) {
path = append(it.path, node.Key[:len(node.Key)-1]...)
} else {
path = append(it.path, node.Key...)
}
return state, &parent.index, path, nil
}
} else if hash, ok := parent.node.(hashNode); ok {
// Hash node, resolve the hash child from the database
if parent.index < 0 {
node, err := it.trie.resolveHash(hash, nil, nil)
if err != nil {
return it.stack[len(it.stack)-1], &parent.index, it.path, err
}
state := &nodeIteratorState{
hash: common.BytesToHash(hash),
node: node,
parent: ancestor,
index: -1,
pathlen: len(it.path),
}
return state, &parent.index, it.path, nil
state, path, ok := it.nextChild(parent, ancestor)
if ok {
if err := state.resolve(it.trie, path); err != nil {
return parent, &parent.index, path, err
}
return state, &parent.index, path, nil
}
// No more child nodes, move back up.
it.pop()
}
return nil, nil, nil, iteratorEnd
}
func (st *nodeIteratorState) resolve(tr *Trie, path []byte) error {
if hash, ok := st.node.(hashNode); ok {
resolved, err := tr.resolveHash(hash, path)
if err != nil {
return err
}
st.node = resolved
st.hash = common.BytesToHash(hash)
}
return nil
}
func (it *nodeIterator) nextChild(parent *nodeIteratorState, ancestor common.Hash) (*nodeIteratorState, []byte, bool) {
switch node := parent.node.(type) {
case *fullNode:
// Full node, move to the first non-nil child.
for i := parent.index + 1; i < len(node.Children); i++ {
child := node.Children[i]
if child != nil {
hash, _ := child.cache()
state := &nodeIteratorState{
hash: common.BytesToHash(hash),
node: child,
parent: ancestor,
index: -1,
pathlen: len(it.path),
}
path := append(it.path, byte(i))
parent.index = i - 1
return state, path, true
}
}
case *shortNode:
// Short node, return the pointer singleton child
if parent.index < 0 {
hash, _ := node.Val.cache()
state := &nodeIteratorState{
hash: common.BytesToHash(hash),
node: node.Val,
parent: ancestor,
index: -1,
pathlen: len(it.path),
}
path := append(it.path, node.Key...)
return state, path, true
}
}
return parent, it.path, false
}
func (it *nodeIterator) push(state *nodeIteratorState, parentIndex *int, path []byte) {
@ -288,23 +314,21 @@ func (it *nodeIterator) pop() {
}
func compareNodes(a, b NodeIterator) int {
cmp := bytes.Compare(a.Path(), b.Path())
if cmp != 0 {
if cmp := bytes.Compare(a.Path(), b.Path()); cmp != 0 {
return cmp
}
if a.Leaf() && !b.Leaf() {
return -1
} else if b.Leaf() && !a.Leaf() {
return 1
}
cmp = bytes.Compare(a.Hash().Bytes(), b.Hash().Bytes())
if cmp != 0 {
if cmp := bytes.Compare(a.Hash().Bytes(), b.Hash().Bytes()); cmp != 0 {
return cmp
}
return bytes.Compare(a.LeafBlob(), b.LeafBlob())
if a.Leaf() && b.Leaf() {
return bytes.Compare(a.LeafBlob(), b.LeafBlob())
}
return 0
}
type differenceIterator struct {
@ -341,6 +365,10 @@ func (it *differenceIterator) LeafBlob() []byte {
return it.b.LeafBlob()
}
func (it *differenceIterator) LeafKey() []byte {
return it.b.LeafKey()
}
func (it *differenceIterator) Path() []byte {
return it.b.Path()
}
@ -410,7 +438,6 @@ func (h *nodeIteratorHeap) Pop() interface{} {
type unionIterator struct {
items *nodeIteratorHeap // Nodes returned are the union of the ones in these iterators
count int // Number of nodes scanned across all tries
err error // The error, if one has been encountered
}
// NewUnionIterator constructs a NodeIterator that iterates over elements in the union
@ -421,9 +448,7 @@ func NewUnionIterator(iters []NodeIterator) (NodeIterator, *int) {
copy(h, iters)
heap.Init(&h)
ui := &unionIterator{
items: &h,
}
ui := &unionIterator{items: &h}
return ui, &ui.count
}
@ -443,6 +468,10 @@ func (it *unionIterator) LeafBlob() []byte {
return (*it.items)[0].LeafBlob()
}
func (it *unionIterator) LeafKey() []byte {
return (*it.items)[0].LeafKey()
}
func (it *unionIterator) Path() []byte {
return (*it.items)[0].Path()
}