neo-go/pkg/core/mpt/batch.go
AnnaShaleva 3fed7b8eec core: handle empty MPT batch properly
It's OK to have it.
2021-10-27 18:44:39 +03:00

292 lines
7.5 KiB
Go

package mpt
import (
"bytes"
"sort"
)
// Batch is batch of storage changes.
// It stores key-value pairs in a sorted state.
type Batch struct {
kv []keyValue
}
type keyValue struct {
key []byte
value []byte
}
// Add adds key-value pair to batch.
// If there is an item with the specified key, it is replaced.
func (b *Batch) Add(key []byte, value []byte) {
path := toNibbles(key)
i := sort.Search(len(b.kv), func(i int) bool {
return bytes.Compare(path, b.kv[i].key) <= 0
})
if i == len(b.kv) {
b.kv = append(b.kv, keyValue{path, value})
} else if bytes.Equal(b.kv[i].key, path) {
b.kv[i].value = value
} else {
b.kv = append(b.kv, keyValue{})
copy(b.kv[i+1:], b.kv[i:])
b.kv[i].key = path
b.kv[i].value = value
}
}
// PutBatch puts batch to trie.
// It is not atomic (and probably cannot be without substantial slow-down)
// and returns number of elements processed.
// If an error is returned, the trie may be in the inconsistent state in case of storage failures.
// This is due to the fact that we can remove multiple children from the branch node simultaneously
// and won't strip the resulting branch node.
// However it is used mostly after the block processing to update MPT and error is not expected.
func (t *Trie) PutBatch(b Batch) (int, error) {
if len(b.kv) == 0 {
return 0, nil
}
r, n, err := t.putBatch(b.kv)
t.root = r
return n, err
}
func (t *Trie) putBatch(kv []keyValue) (Node, int, error) {
return t.putBatchIntoNode(t.root, kv)
}
func (t *Trie) putBatchIntoNode(curr Node, kv []keyValue) (Node, int, error) {
switch n := curr.(type) {
case *LeafNode:
return t.putBatchIntoLeaf(n, kv)
case *BranchNode:
return t.putBatchIntoBranch(n, kv)
case *ExtensionNode:
return t.putBatchIntoExtension(n, kv)
case *HashNode:
return t.putBatchIntoHash(n, kv)
case EmptyNode:
return t.putBatchIntoEmpty(kv)
default:
panic("invalid MPT node type")
}
}
func (t *Trie) putBatchIntoLeaf(curr *LeafNode, kv []keyValue) (Node, int, error) {
t.removeRef(curr.Hash(), curr.Bytes())
return t.newSubTrieMany(nil, kv, curr.value)
}
func (t *Trie) putBatchIntoBranch(curr *BranchNode, kv []keyValue) (Node, int, error) {
return t.addToBranch(curr, kv, true)
}
func (t *Trie) mergeExtension(prefix []byte, sub Node) (Node, error) {
switch sn := sub.(type) {
case *ExtensionNode:
t.removeRef(sn.Hash(), sn.bytes)
sn.key = append(prefix, sn.key...)
sn.invalidateCache()
t.addRef(sn.Hash(), sn.bytes)
return sn, nil
case EmptyNode:
return sn, nil
case *HashNode:
n, err := t.getFromStore(sn.Hash())
if err != nil {
return sn, err
}
return t.mergeExtension(prefix, n)
default:
if len(prefix) != 0 {
e := NewExtensionNode(prefix, sub)
t.addRef(e.Hash(), e.bytes)
return e, nil
}
return sub, nil
}
}
func (t *Trie) putBatchIntoExtension(curr *ExtensionNode, kv []keyValue) (Node, int, error) {
t.removeRef(curr.Hash(), curr.bytes)
common := lcpMany(kv)
pref := lcp(common, curr.key)
if len(pref) == len(curr.key) {
// Extension must be split into new nodes.
stripPrefix(len(curr.key), kv)
sub, n, err := t.putBatchIntoNode(curr.next, kv)
if err == nil {
sub, err = t.mergeExtension(pref, sub)
}
return sub, n, err
}
if len(pref) != 0 {
stripPrefix(len(pref), kv)
sub, n, err := t.putBatchIntoExtensionNoPrefix(curr.key[len(pref):], curr.next, kv)
if err == nil {
sub, err = t.mergeExtension(pref, sub)
}
return sub, n, err
}
return t.putBatchIntoExtensionNoPrefix(curr.key, curr.next, kv)
}
func (t *Trie) putBatchIntoExtensionNoPrefix(key []byte, next Node, kv []keyValue) (Node, int, error) {
b := NewBranchNode()
if len(key) > 1 {
b.Children[key[0]] = t.newSubTrie(key[1:], next, false)
} else {
b.Children[key[0]] = next
}
return t.addToBranch(b, kv, false)
}
func isEmpty(n Node) bool {
_, ok := n.(EmptyNode)
return ok
}
// addToBranch puts items into the branch node assuming b is not yet in trie.
func (t *Trie) addToBranch(b *BranchNode, kv []keyValue, inTrie bool) (Node, int, error) {
if inTrie {
t.removeRef(b.Hash(), b.bytes)
}
// Error during iterate means some storage failure (i.e. some hash node cannot be
// retrieved from storage). This can leave trie in inconsistent state, because
// it can be impossible to strip branch node after it has been changed.
// Consider a branch with 10 children, first 9 of which are deleted and the remaining one
// is a leaf node replaced by a hash node missing from storage.
// This can't be fixed easily because we need to _revert_ changes in reference counts
// for children which were updated successfully. But storage access errors means we are
// in a bad state anyway.
n, err := t.iterateBatch(kv, func(c byte, kv []keyValue) (int, error) {
child, n, err := t.putBatchIntoNode(b.Children[c], kv)
b.Children[c] = child
return n, err
})
if inTrie && n != 0 {
b.invalidateCache()
}
// Even if some of the children can't be put, we need to try to strip branch
// and possibly update refcounts.
nd, bErr := t.stripBranch(b)
if err == nil {
err = bErr
}
return nd, n, err
}
// stripsBranch strips branch node after incomplete batch put.
// It assumes there is no reference to b in trie.
func (t *Trie) stripBranch(b *BranchNode) (Node, error) {
var n int
var lastIndex byte
for i := range b.Children {
if !isEmpty(b.Children[i]) {
n++
lastIndex = byte(i)
}
}
switch {
case n == 0:
return EmptyNode{}, nil
case n == 1:
if lastIndex != lastChild {
return t.mergeExtension([]byte{lastIndex}, b.Children[lastIndex])
}
return b.Children[lastIndex], nil
default:
t.addRef(b.Hash(), b.bytes)
return b, nil
}
}
func (t *Trie) iterateBatch(kv []keyValue, f func(c byte, kv []keyValue) (int, error)) (int, error) {
var n int
for len(kv) != 0 {
c, i := getLastIndex(kv)
if c != lastChild {
stripPrefix(1, kv[:i])
}
sub, err := f(c, kv[:i])
n += sub
if err != nil {
return n, err
}
kv = kv[i:]
}
return n, nil
}
func (t *Trie) putBatchIntoEmpty(kv []keyValue) (Node, int, error) {
common := lcpMany(kv)
stripPrefix(len(common), kv)
return t.newSubTrieMany(common, kv, nil)
}
func (t *Trie) putBatchIntoHash(curr *HashNode, kv []keyValue) (Node, int, error) {
result, err := t.getFromStore(curr.hash)
if err != nil {
return curr, 0, err
}
return t.putBatchIntoNode(result, kv)
}
// Creates new subtrie from provided key-value pairs.
// Items in kv must have no common prefix.
// If there are any deletions in kv, return error.
// kv is not empty.
// kv is sorted by key.
// value is current value stored by prefix.
func (t *Trie) newSubTrieMany(prefix []byte, kv []keyValue, value []byte) (Node, int, error) {
if len(kv[0].key) == 0 {
if kv[0].value == nil {
if len(kv) == 1 {
return EmptyNode{}, 1, nil
}
node, n, err := t.newSubTrieMany(prefix, kv[1:], nil)
return node, n + 1, err
}
if len(kv) == 1 {
return t.newSubTrie(prefix, NewLeafNode(kv[0].value), true), 1, nil
}
value = kv[0].value
}
// Prefix is empty and we have at least 2 children.
b := NewBranchNode()
if value != nil {
// Empty key is always first.
leaf := NewLeafNode(value)
t.addRef(leaf.Hash(), leaf.bytes)
b.Children[lastChild] = leaf
}
nd, n, err := t.addToBranch(b, kv, false)
if err == nil {
nd, err = t.mergeExtension(prefix, nd)
}
return nd, n, err
}
func stripPrefix(n int, kv []keyValue) {
for i := range kv {
kv[i].key = kv[i].key[n:]
}
}
func getLastIndex(kv []keyValue) (byte, int) {
if len(kv[0].key) == 0 {
return lastChild, 1
}
c := kv[0].key[0]
for i := range kv[1:] {
if kv[i+1].key[0] != c {
return c, i + 1
}
}
return c, len(kv)
}