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trie: improve the node iterator seek operation (#22470)

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This change improves the efficiency of the nodeIterator seek
operation. Previously, seek essentially ran the iterator forward
until it found the matching node. With this change, it skips
over fullnode children and avoids resolving them from the database.
This commit is contained in:
Martin Holst Swende 2021-04-21 12:25:26 +02:00 committed by GitHub
parent 3e68d627b1
commit 4b783c0064
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 202 additions and 24 deletions
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145
trie/iterator.go
View File

@ -243,7 +243,7 @@ func (it *nodeIterator) seek(prefix []byte) error {
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))
state, parentIndex, path, err := it.peekSeek(key)
if err == errIteratorEnd {
return errIteratorEnd
} else if err != nil {
@ -255,16 +255,21 @@ func (it *nodeIterator) seek(prefix []byte) error {
}
}
// init initializes the the iterator.
func (it *nodeIterator) init() (*nodeIteratorState, error) {
root := it.trie.Hash()
state := &nodeIteratorState{node: it.trie.root, index: -1}
if root != emptyRoot {
state.hash = root
}
return state, state.resolve(it.trie, nil)
}
// peek creates the next state of the iterator.
func (it *nodeIterator) peek(descend bool) (*nodeIteratorState, *int, []byte, error) {
// Initialize the iterator if we've just started.
if len(it.stack) == 0 {
// Initialize the iterator if we've just started.
root := it.trie.Hash()
state := &nodeIteratorState{node: it.trie.root, index: -1}
if root != emptyRoot {
state.hash = root
}
err := state.resolve(it.trie, nil)
state, err := it.init()
return state, nil, nil, err
}
if !descend {
@ -292,6 +297,39 @@ func (it *nodeIterator) peek(descend bool) (*nodeIteratorState, *int, []byte, er
return nil, nil, nil, errIteratorEnd
}
// peekSeek is like peek, but it also tries to skip resolving hashes by skipping
// over the siblings that do not lead towards the desired seek position.
func (it *nodeIterator) peekSeek(seekKey []byte) (*nodeIteratorState, *int, []byte, error) {
// Initialize the iterator if we've just started.
if len(it.stack) == 0 {
state, err := it.init()
return state, nil, nil, err
}
if !bytes.HasPrefix(seekKey, it.path) {
// If we're skipping children, pop the current node first
it.pop()
}
// Continue iteration to the next child
for len(it.stack) > 0 {
parent := it.stack[len(it.stack)-1]
ancestor := parent.hash
if (ancestor == common.Hash{}) {
ancestor = parent.parent
}
state, path, ok := it.nextChildAt(parent, ancestor, seekKey)
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, errIteratorEnd
}
func (st *nodeIteratorState) resolve(tr *Trie, path []byte) error {
if hash, ok := st.node.(hashNode); ok {
resolved, err := tr.resolveHash(hash, path)
@ -304,25 +342,38 @@ func (st *nodeIteratorState) resolve(tr *Trie, path []byte) error {
return nil
}
func findChild(n *fullNode, index int, path []byte, ancestor common.Hash) (node, *nodeIteratorState, []byte, int) {
var (
child node
state *nodeIteratorState
childPath []byte
)
for ; index < len(n.Children); index++ {
if n.Children[index] != nil {
child = n.Children[index]
hash, _ := child.cache()
state = &nodeIteratorState{
hash: common.BytesToHash(hash),
node: child,
parent: ancestor,
index: -1,
pathlen: len(path),
}
childPath = append(childPath, path...)
childPath = append(childPath, byte(index))
return child, state, childPath, index
}
}
return nil, nil, nil, 0
}
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
}
//Full node, move to the first non-nil child.
if child, state, path, index := findChild(node, parent.index+1, it.path, ancestor); child != nil {
parent.index = index - 1
return state, path, true
}
case *shortNode:
// Short node, return the pointer singleton child
@ -342,6 +393,52 @@ func (it *nodeIterator) nextChild(parent *nodeIteratorState, ancestor common.Has
return parent, it.path, false
}
// nextChildAt is similar to nextChild, except that it targets a child as close to the
// target key as possible, thus skipping siblings.
func (it *nodeIterator) nextChildAt(parent *nodeIteratorState, ancestor common.Hash, key []byte) (*nodeIteratorState, []byte, bool) {
switch n := parent.node.(type) {
case *fullNode:
// Full node, move to the first non-nil child before the desired key position
child, state, path, index := findChild(n, parent.index+1, it.path, ancestor)
if child == nil {
// No more children in this fullnode
return parent, it.path, false
}
// If the child we found is already past the seek position, just return it.
if bytes.Compare(path, key) >= 0 {
parent.index = index - 1
return state, path, true
}
// The child is before the seek position. Try advancing
for {
nextChild, nextState, nextPath, nextIndex := findChild(n, index+1, it.path, ancestor)
// If we run out of children, or skipped past the target, return the
// previous one
if nextChild == nil || bytes.Compare(nextPath, key) >= 0 {
parent.index = index - 1
return state, path, true
}
// We found a better child closer to the target
state, path, index = nextState, nextPath, nextIndex
}
case *shortNode:
// Short node, return the pointer singleton child
if parent.index < 0 {
hash, _ := n.Val.cache()
state := &nodeIteratorState{
hash: common.BytesToHash(hash),
node: n.Val,
parent: ancestor,
index: -1,
pathlen: len(it.path),
}
path := append(it.path, n.Key...)
return state, path, true
}
}
return parent, it.path, false
}
func (it *nodeIterator) push(state *nodeIteratorState, parentIndex *int, path []byte) {
it.path = path
it.stack = append(it.stack, state)

81
trie/iterator_test.go
View File

@ -18,11 +18,14 @@ package trie
import (
"bytes"
"encoding/binary"
"fmt"
"math/rand"
"testing"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/ethdb/memorydb"
)
@ -440,3 +443,81 @@ func checkIteratorNoDups(t *testing.T, it NodeIterator, seen map[string]bool) in
}
return len(seen)
}
type loggingDb struct {
getCount uint64
backend ethdb.KeyValueStore
}
func (l *loggingDb) Has(key []byte) (bool, error) {
return l.backend.Has(key)
}
func (l *loggingDb) Get(key []byte) ([]byte, error) {
l.getCount++
return l.backend.Get(key)
}
func (l *loggingDb) Put(key []byte, value []byte) error {
return l.backend.Put(key, value)
}
func (l *loggingDb) Delete(key []byte) error {
return l.backend.Delete(key)
}
func (l *loggingDb) NewBatch() ethdb.Batch {
return l.backend.NewBatch()
}
func (l *loggingDb) NewIterator(prefix []byte, start []byte) ethdb.Iterator {
fmt.Printf("NewIterator\n")
return l.backend.NewIterator(prefix, start)
}
func (l *loggingDb) Stat(property string) (string, error) {
return l.backend.Stat(property)
}
func (l *loggingDb) Compact(start []byte, limit []byte) error {
return l.backend.Compact(start, limit)
}
func (l *loggingDb) Close() error {
return l.backend.Close()
}
// makeLargeTestTrie create a sample test trie
func makeLargeTestTrie() (*Database, *SecureTrie, *loggingDb) {
// Create an empty trie
logDb := &loggingDb{0, memorydb.New()}
triedb := NewDatabase(logDb)
trie, _ := NewSecure(common.Hash{}, triedb)
// Fill it with some arbitrary data
for i := 0; i < 10000; i++ {
key := make([]byte, 32)
val := make([]byte, 32)
binary.BigEndian.PutUint64(key, uint64(i))
binary.BigEndian.PutUint64(val, uint64(i))
key = crypto.Keccak256(key)
val = crypto.Keccak256(val)
trie.Update(key, val)
}
trie.Commit(nil)
// Return the generated trie
return triedb, trie, logDb
}
// Tests that the node iterator indeed walks over the entire database contents.
func TestNodeIteratorLargeTrie(t *testing.T) {
// Create some arbitrary test trie to iterate
db, trie, logDb := makeLargeTestTrie()
db.Cap(0) // flush everything
// Do a seek operation
trie.NodeIterator(common.FromHex("0x77667766776677766778855885885885"))
// master: 24 get operations
// this pr: 5 get operations
if have, want := logDb.getCount, uint64(5); have != want {
t.Fatalf("Too many lookups during seek, have %d want %d", have, want)
}
}