plugeth/trie/trie.go
Evolution404 732a6a3666
trie: small optimization of delete in fullNode case (#22979)
When deleting in fullNode, and the new child node nn is not nil, there is no need
to check the number of non-nil entries in the node. This is because the fullNode 
must've contained at least two children before deletion, so there must be another
child node other than nn.

Co-authored-by: Felix Lange <fjl@twurst.com>
2021-06-20 15:59:00 +02:00

581 lines
18 KiB
Go

// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// Package trie implements Merkle Patricia Tries.
package trie
import (
"bytes"
"errors"
"fmt"
"sync"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/log"
)
var (
// emptyRoot is the known root hash of an empty trie.
emptyRoot = common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
// emptyState is the known hash of an empty state trie entry.
emptyState = crypto.Keccak256Hash(nil)
)
// LeafCallback is a callback type invoked when a trie operation reaches a leaf
// node.
//
// The paths is a path tuple identifying a particular trie node either in a single
// trie (account) or a layered trie (account -> storage). Each path in the tuple
// is in the raw format(32 bytes).
//
// The hexpath is a composite hexary path identifying the trie node. All the key
// bytes are converted to the hexary nibbles and composited with the parent path
// if the trie node is in a layered trie.
//
// It's used by state sync and commit to allow handling external references
// between account and storage tries. And also it's used in the state healing
// for extracting the raw states(leaf nodes) with corresponding paths.
type LeafCallback func(paths [][]byte, hexpath []byte, leaf []byte, parent common.Hash) error
// Trie is a Merkle Patricia Trie.
// The zero value is an empty trie with no database.
// Use New to create a trie that sits on top of a database.
//
// Trie is not safe for concurrent use.
type Trie struct {
db *Database
root node
// Keep track of the number leafs which have been inserted since the last
// hashing operation. This number will not directly map to the number of
// actually unhashed nodes
unhashed int
}
// newFlag returns the cache flag value for a newly created node.
func (t *Trie) newFlag() nodeFlag {
return nodeFlag{dirty: true}
}
// New creates a trie with an existing root node from db.
//
// If root is the zero hash or the sha3 hash of an empty string, the
// trie is initially empty and does not require a database. Otherwise,
// New will panic if db is nil and returns a MissingNodeError if root does
// not exist in the database. Accessing the trie loads nodes from db on demand.
func New(root common.Hash, db *Database) (*Trie, error) {
if db == nil {
panic("trie.New called without a database")
}
trie := &Trie{
db: db,
}
if root != (common.Hash{}) && root != emptyRoot {
rootnode, err := trie.resolveHash(root[:], nil)
if err != nil {
return nil, err
}
trie.root = rootnode
}
return trie, nil
}
// NodeIterator returns an iterator that returns nodes of the trie. Iteration starts at
// the key after the given start key.
func (t *Trie) NodeIterator(start []byte) NodeIterator {
return newNodeIterator(t, start)
}
// Get returns the value for key stored in the trie.
// The value bytes must not be modified by the caller.
func (t *Trie) Get(key []byte) []byte {
res, err := t.TryGet(key)
if err != nil {
log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
}
return res
}
// TryGet returns the value for key stored in the trie.
// The value bytes must not be modified by the caller.
// If a node was not found in the database, a MissingNodeError is returned.
func (t *Trie) TryGet(key []byte) ([]byte, error) {
value, newroot, didResolve, err := t.tryGet(t.root, keybytesToHex(key), 0)
if err == nil && didResolve {
t.root = newroot
}
return value, err
}
func (t *Trie) tryGet(origNode node, key []byte, pos int) (value []byte, newnode node, didResolve bool, err error) {
switch n := (origNode).(type) {
case nil:
return nil, nil, false, nil
case valueNode:
return n, n, false, nil
case *shortNode:
if len(key)-pos < len(n.Key) || !bytes.Equal(n.Key, key[pos:pos+len(n.Key)]) {
// key not found in trie
return nil, n, false, nil
}
value, newnode, didResolve, err = t.tryGet(n.Val, key, pos+len(n.Key))
if err == nil && didResolve {
n = n.copy()
n.Val = newnode
}
return value, n, didResolve, err
case *fullNode:
value, newnode, didResolve, err = t.tryGet(n.Children[key[pos]], key, pos+1)
if err == nil && didResolve {
n = n.copy()
n.Children[key[pos]] = newnode
}
return value, n, didResolve, err
case hashNode:
child, err := t.resolveHash(n, key[:pos])
if err != nil {
return nil, n, true, err
}
value, newnode, _, err := t.tryGet(child, key, pos)
return value, newnode, true, err
default:
panic(fmt.Sprintf("%T: invalid node: %v", origNode, origNode))
}
}
// TryGetNode attempts to retrieve a trie node by compact-encoded path. It is not
// possible to use keybyte-encoding as the path might contain odd nibbles.
func (t *Trie) TryGetNode(path []byte) ([]byte, int, error) {
item, newroot, resolved, err := t.tryGetNode(t.root, compactToHex(path), 0)
if err != nil {
return nil, resolved, err
}
if resolved > 0 {
t.root = newroot
}
if item == nil {
return nil, resolved, nil
}
return item, resolved, err
}
func (t *Trie) tryGetNode(origNode node, path []byte, pos int) (item []byte, newnode node, resolved int, err error) {
// If we reached the requested path, return the current node
if pos >= len(path) {
// Although we most probably have the original node expanded, encoding
// that into consensus form can be nasty (needs to cascade down) and
// time consuming. Instead, just pull the hash up from disk directly.
var hash hashNode
if node, ok := origNode.(hashNode); ok {
hash = node
} else {
hash, _ = origNode.cache()
}
if hash == nil {
return nil, origNode, 0, errors.New("non-consensus node")
}
blob, err := t.db.Node(common.BytesToHash(hash))
return blob, origNode, 1, err
}
// Path still needs to be traversed, descend into children
switch n := (origNode).(type) {
case nil:
// Non-existent path requested, abort
return nil, nil, 0, nil
case valueNode:
// Path prematurely ended, abort
return nil, nil, 0, nil
case *shortNode:
if len(path)-pos < len(n.Key) || !bytes.Equal(n.Key, path[pos:pos+len(n.Key)]) {
// Path branches off from short node
return nil, n, 0, nil
}
item, newnode, resolved, err = t.tryGetNode(n.Val, path, pos+len(n.Key))
if err == nil && resolved > 0 {
n = n.copy()
n.Val = newnode
}
return item, n, resolved, err
case *fullNode:
item, newnode, resolved, err = t.tryGetNode(n.Children[path[pos]], path, pos+1)
if err == nil && resolved > 0 {
n = n.copy()
n.Children[path[pos]] = newnode
}
return item, n, resolved, err
case hashNode:
child, err := t.resolveHash(n, path[:pos])
if err != nil {
return nil, n, 1, err
}
item, newnode, resolved, err := t.tryGetNode(child, path, pos)
return item, newnode, resolved + 1, err
default:
panic(fmt.Sprintf("%T: invalid node: %v", origNode, origNode))
}
}
// Update associates key with value in the trie. Subsequent calls to
// Get will return value. If value has length zero, any existing value
// is deleted from the trie and calls to Get will return nil.
//
// The value bytes must not be modified by the caller while they are
// stored in the trie.
func (t *Trie) Update(key, value []byte) {
if err := t.TryUpdate(key, value); err != nil {
log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
}
}
// TryUpdate associates key with value in the trie. Subsequent calls to
// Get will return value. If value has length zero, any existing value
// is deleted from the trie and calls to Get will return nil.
//
// The value bytes must not be modified by the caller while they are
// stored in the trie.
//
// If a node was not found in the database, a MissingNodeError is returned.
func (t *Trie) TryUpdate(key, value []byte) error {
t.unhashed++
k := keybytesToHex(key)
if len(value) != 0 {
_, n, err := t.insert(t.root, nil, k, valueNode(value))
if err != nil {
return err
}
t.root = n
} else {
_, n, err := t.delete(t.root, nil, k)
if err != nil {
return err
}
t.root = n
}
return nil
}
func (t *Trie) insert(n node, prefix, key []byte, value node) (bool, node, error) {
if len(key) == 0 {
if v, ok := n.(valueNode); ok {
return !bytes.Equal(v, value.(valueNode)), value, nil
}
return true, value, nil
}
switch n := n.(type) {
case *shortNode:
matchlen := prefixLen(key, n.Key)
// If the whole key matches, keep this short node as is
// and only update the value.
if matchlen == len(n.Key) {
dirty, nn, err := t.insert(n.Val, append(prefix, key[:matchlen]...), key[matchlen:], value)
if !dirty || err != nil {
return false, n, err
}
return true, &shortNode{n.Key, nn, t.newFlag()}, nil
}
// Otherwise branch out at the index where they differ.
branch := &fullNode{flags: t.newFlag()}
var err error
_, branch.Children[n.Key[matchlen]], err = t.insert(nil, append(prefix, n.Key[:matchlen+1]...), n.Key[matchlen+1:], n.Val)
if err != nil {
return false, nil, err
}
_, branch.Children[key[matchlen]], err = t.insert(nil, append(prefix, key[:matchlen+1]...), key[matchlen+1:], value)
if err != nil {
return false, nil, err
}
// Replace this shortNode with the branch if it occurs at index 0.
if matchlen == 0 {
return true, branch, nil
}
// Otherwise, replace it with a short node leading up to the branch.
return true, &shortNode{key[:matchlen], branch, t.newFlag()}, nil
case *fullNode:
dirty, nn, err := t.insert(n.Children[key[0]], append(prefix, key[0]), key[1:], value)
if !dirty || err != nil {
return false, n, err
}
n = n.copy()
n.flags = t.newFlag()
n.Children[key[0]] = nn
return true, n, nil
case nil:
return true, &shortNode{key, value, t.newFlag()}, nil
case hashNode:
// We've hit a part of the trie that isn't loaded yet. Load
// the node and insert into it. This leaves all child nodes on
// the path to the value in the trie.
rn, err := t.resolveHash(n, prefix)
if err != nil {
return false, nil, err
}
dirty, nn, err := t.insert(rn, prefix, key, value)
if !dirty || err != nil {
return false, rn, err
}
return true, nn, nil
default:
panic(fmt.Sprintf("%T: invalid node: %v", n, n))
}
}
// Delete removes any existing value for key from the trie.
func (t *Trie) Delete(key []byte) {
if err := t.TryDelete(key); err != nil {
log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
}
}
// TryDelete removes any existing value for key from the trie.
// If a node was not found in the database, a MissingNodeError is returned.
func (t *Trie) TryDelete(key []byte) error {
t.unhashed++
k := keybytesToHex(key)
_, n, err := t.delete(t.root, nil, k)
if err != nil {
return err
}
t.root = n
return nil
}
// delete returns the new root of the trie with key deleted.
// It reduces the trie to minimal form by simplifying
// nodes on the way up after deleting recursively.
func (t *Trie) delete(n node, prefix, key []byte) (bool, node, error) {
switch n := n.(type) {
case *shortNode:
matchlen := prefixLen(key, n.Key)
if matchlen < len(n.Key) {
return false, n, nil // don't replace n on mismatch
}
if matchlen == len(key) {
return true, nil, nil // remove n entirely for whole matches
}
// The key is longer than n.Key. Remove the remaining suffix
// from the subtrie. Child can never be nil here since the
// subtrie must contain at least two other values with keys
// longer than n.Key.
dirty, child, err := t.delete(n.Val, append(prefix, key[:len(n.Key)]...), key[len(n.Key):])
if !dirty || err != nil {
return false, n, err
}
switch child := child.(type) {
case *shortNode:
// Deleting from the subtrie reduced it to another
// short node. Merge the nodes to avoid creating a
// shortNode{..., shortNode{...}}. Use concat (which
// always creates a new slice) instead of append to
// avoid modifying n.Key since it might be shared with
// other nodes.
return true, &shortNode{concat(n.Key, child.Key...), child.Val, t.newFlag()}, nil
default:
return true, &shortNode{n.Key, child, t.newFlag()}, nil
}
case *fullNode:
dirty, nn, err := t.delete(n.Children[key[0]], append(prefix, key[0]), key[1:])
if !dirty || err != nil {
return false, n, err
}
n = n.copy()
n.flags = t.newFlag()
n.Children[key[0]] = nn
// Because n is a full node, it must've contained at least two children
// before the delete operation. If the new child value is non-nil, n still
// has at least two children after the deletion, and cannot be reduced to
// a short node.
if nn != nil {
return true, n, nil
}
// Reduction:
// Check how many non-nil entries are left after deleting and
// reduce the full node to a short node if only one entry is
// left. Since n must've contained at least two children
// before deletion (otherwise it would not be a full node) n
// can never be reduced to nil.
//
// When the loop is done, pos contains the index of the single
// value that is left in n or -2 if n contains at least two
// values.
pos := -1
for i, cld := range &n.Children {
if cld != nil {
if pos == -1 {
pos = i
} else {
pos = -2
break
}
}
}
if pos >= 0 {
if pos != 16 {
// If the remaining entry is a short node, it replaces
// n and its key gets the missing nibble tacked to the
// front. This avoids creating an invalid
// shortNode{..., shortNode{...}}. Since the entry
// might not be loaded yet, resolve it just for this
// check.
cnode, err := t.resolve(n.Children[pos], prefix)
if err != nil {
return false, nil, err
}
if cnode, ok := cnode.(*shortNode); ok {
k := append([]byte{byte(pos)}, cnode.Key...)
return true, &shortNode{k, cnode.Val, t.newFlag()}, nil
}
}
// Otherwise, n is replaced by a one-nibble short node
// containing the child.
return true, &shortNode{[]byte{byte(pos)}, n.Children[pos], t.newFlag()}, nil
}
// n still contains at least two values and cannot be reduced.
return true, n, nil
case valueNode:
return true, nil, nil
case nil:
return false, nil, nil
case hashNode:
// We've hit a part of the trie that isn't loaded yet. Load
// the node and delete from it. This leaves all child nodes on
// the path to the value in the trie.
rn, err := t.resolveHash(n, prefix)
if err != nil {
return false, nil, err
}
dirty, nn, err := t.delete(rn, prefix, key)
if !dirty || err != nil {
return false, rn, err
}
return true, nn, nil
default:
panic(fmt.Sprintf("%T: invalid node: %v (%v)", n, n, key))
}
}
func concat(s1 []byte, s2 ...byte) []byte {
r := make([]byte, len(s1)+len(s2))
copy(r, s1)
copy(r[len(s1):], s2)
return r
}
func (t *Trie) resolve(n node, prefix []byte) (node, error) {
if n, ok := n.(hashNode); ok {
return t.resolveHash(n, prefix)
}
return n, nil
}
func (t *Trie) resolveHash(n hashNode, prefix []byte) (node, error) {
hash := common.BytesToHash(n)
if node := t.db.node(hash); node != nil {
return node, nil
}
return nil, &MissingNodeError{NodeHash: hash, Path: prefix}
}
// Hash returns the root hash of the trie. It does not write to the
// database and can be used even if the trie doesn't have one.
func (t *Trie) Hash() common.Hash {
hash, cached, _ := t.hashRoot()
t.root = cached
return common.BytesToHash(hash.(hashNode))
}
// Commit writes all nodes to the trie's memory database, tracking the internal
// and external (for account tries) references.
func (t *Trie) Commit(onleaf LeafCallback) (root common.Hash, err error) {
if t.db == nil {
panic("commit called on trie with nil database")
}
if t.root == nil {
return emptyRoot, nil
}
// Derive the hash for all dirty nodes first. We hold the assumption
// in the following procedure that all nodes are hashed.
rootHash := t.Hash()
h := newCommitter()
defer returnCommitterToPool(h)
// Do a quick check if we really need to commit, before we spin
// up goroutines. This can happen e.g. if we load a trie for reading storage
// values, but don't write to it.
if _, dirty := t.root.cache(); !dirty {
return rootHash, nil
}
var wg sync.WaitGroup
if onleaf != nil {
h.onleaf = onleaf
h.leafCh = make(chan *leaf, leafChanSize)
wg.Add(1)
go func() {
defer wg.Done()
h.commitLoop(t.db)
}()
}
var newRoot hashNode
newRoot, err = h.Commit(t.root, t.db)
if onleaf != nil {
// The leafch is created in newCommitter if there was an onleaf callback
// provided. The commitLoop only _reads_ from it, and the commit
// operation was the sole writer. Therefore, it's safe to close this
// channel here.
close(h.leafCh)
wg.Wait()
}
if err != nil {
return common.Hash{}, err
}
t.root = newRoot
return rootHash, nil
}
// hashRoot calculates the root hash of the given trie
func (t *Trie) hashRoot() (node, node, error) {
if t.root == nil {
return hashNode(emptyRoot.Bytes()), nil, nil
}
// If the number of changes is below 100, we let one thread handle it
h := newHasher(t.unhashed >= 100)
defer returnHasherToPool(h)
hashed, cached := h.hash(t.root, true)
t.unhashed = 0
return hashed, cached, nil
}
// Reset drops the referenced root node and cleans all internal state.
func (t *Trie) Reset() {
t.root = nil
t.unhashed = 0
}