Consensus flaw during block processing

@@ -34,6 +34,7 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
 	"golang.org/x/crypto/sha3"
 )
 
@@ -220,8 +221,8 @@ func (pre *Prestate) Apply(vmConfig vm.Config, chainConfig *params.ChainConfig,
 	}
 	execRs := &ExecutionResult{
 		StateRoot:   root,
-		TxRoot:      types.DeriveSha(includedTxs),
-		ReceiptRoot: types.DeriveSha(receipts),
+		TxRoot:      types.DeriveSha(includedTxs, new(trie.Trie)),
+		ReceiptRoot: types.DeriveSha(receipts, new(trie.Trie)),
 		Bloom:       types.CreateBloom(receipts),
 		LogsHash:    rlpHash(statedb.Logs()),
 		Receipts:    receipts,

@@ -248,7 +248,7 @@ func (e *NoRewardEngine) FinalizeAndAssemble(chain consensus.ChainHeaderReader,
 		header.Root = statedb.IntermediateRoot(chain.Config().IsEIP158(header.Number))
 
 		// Header seems complete, assemble into a block and return
-		return types.NewBlock(header, txs, uncles, receipts), nil
+		return types.NewBlock(header, txs, uncles, receipts, new(trie.Trie)), nil
 	}
 }
 

@@ -39,6 +39,7 @@ import (
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/rpc"
+	"github.com/ethereum/go-ethereum/trie"
 	lru "github.com/hashicorp/golang-lru"
 	"golang.org/x/crypto/sha3"
 )
@@ -565,7 +566,7 @@ func (c *Clique) FinalizeAndAssemble(chain consensus.ChainHeaderReader, header *
 	header.UncleHash = types.CalcUncleHash(nil)
 
 	// Assemble and return the final block for sealing
-	return types.NewBlock(header, txs, nil, receipts), nil
+	return types.NewBlock(header, txs, nil, receipts, new(trie.Trie)), nil
 }
 
 // Authorize injects a private key into the consensus engine to mint new blocks

@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
 	"golang.org/x/crypto/sha3"
 )
 
@@ -583,7 +584,7 @@ func (ethash *Ethash) FinalizeAndAssemble(chain consensus.ChainHeaderReader, hea
 	header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number))
 
 	// Header seems complete, assemble into a block and return
-	return types.NewBlock(header, txs, uncles, receipts), nil
+	return types.NewBlock(header, txs, uncles, receipts, new(trie.Trie)), nil
 }
 
 // SealHash returns the hash of a block prior to it being sealed.

@@ -112,7 +112,10 @@ const (
 	// - Version 7
 	//  The following incompatible database changes were added:
 	//    * Use freezer as the ancient database to maintain all ancient data
-	BlockChainVersion uint64 = 7
+	// - Version 8
+	//  The following incompatible database changes were added:
+	//    * New scheme for contract code in order to separate the codes and trie nodes
+	BlockChainVersion uint64 = 8
 )
 
 // CacheConfig contains the configuration values for the trie caching/pruning
@@ -895,12 +898,30 @@ func (bc *BlockChain) GetUnclesInChain(block *types.Block, length int) []*types.
 	return uncles
 }
 
-// TrieNode retrieves a blob of data associated with a trie node (or code hash)
+// TrieNode retrieves a blob of data associated with a trie node
 // either from ephemeral in-memory cache, or from persistent storage.
 func (bc *BlockChain) TrieNode(hash common.Hash) ([]byte, error) {
 	return bc.stateCache.TrieDB().Node(hash)
 }
 
+// ContractCode retrieves a blob of data associated with a contract hash
+// either from ephemeral in-memory cache, or from persistent storage.
+func (bc *BlockChain) ContractCode(hash common.Hash) ([]byte, error) {
+	return bc.stateCache.ContractCode(common.Hash{}, hash)
+}
+
+// ContractCodeWithPrefix retrieves a blob of data associated with a contract
+// hash either from ephemeral in-memory cache, or from persistent storage.
+//
+// If the code doesn't exist in the in-memory cache, check the storage with
+// new code scheme.
+func (bc *BlockChain) ContractCodeWithPrefix(hash common.Hash) ([]byte, error) {
+	type codeReader interface {
+		ContractCodeWithPrefix(addrHash, codeHash common.Hash) ([]byte, error)
+	}
+	return bc.stateCache.(codeReader).ContractCodeWithPrefix(common.Hash{}, hash)
+}
+
 // Stop stops the blockchain service. If any imports are currently in progress
 // it will abort them using the procInterrupt.
 func (bc *BlockChain) Stop() {

@@ -36,6 +36,7 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 // So we can deterministically seed different blockchains
@@ -681,12 +682,12 @@ func TestFastVsFullChains(t *testing.T) {
 		}
 		if fblock, arblock, anblock := fast.GetBlockByHash(hash), archive.GetBlockByHash(hash), ancient.GetBlockByHash(hash); fblock.Hash() != arblock.Hash() || anblock.Hash() != arblock.Hash() {
 			t.Errorf("block #%d [%x]: block mismatch: fastdb %v, ancientdb %v, archivedb %v", num, hash, fblock, anblock, arblock)
-		} else if types.DeriveSha(fblock.Transactions()) != types.DeriveSha(arblock.Transactions()) || types.DeriveSha(anblock.Transactions()) != types.DeriveSha(arblock.Transactions()) {
+		} else if types.DeriveSha(fblock.Transactions(), new(trie.Trie)) != types.DeriveSha(arblock.Transactions(), new(trie.Trie)) || types.DeriveSha(anblock.Transactions(), new(trie.Trie)) != types.DeriveSha(arblock.Transactions(), new(trie.Trie)) {
 			t.Errorf("block #%d [%x]: transactions mismatch: fastdb %v, ancientdb %v, archivedb %v", num, hash, fblock.Transactions(), anblock.Transactions(), arblock.Transactions())
 		} else if types.CalcUncleHash(fblock.Uncles()) != types.CalcUncleHash(arblock.Uncles()) || types.CalcUncleHash(anblock.Uncles()) != types.CalcUncleHash(arblock.Uncles()) {
 			t.Errorf("block #%d [%x]: uncles mismatch: fastdb %v, ancientdb %v, archivedb %v", num, hash, fblock.Uncles(), anblock, arblock.Uncles())
 		}
-		if freceipts, anreceipts, areceipts := rawdb.ReadReceipts(fastDb, hash, *rawdb.ReadHeaderNumber(fastDb, hash), fast.Config()), rawdb.ReadReceipts(ancientDb, hash, *rawdb.ReadHeaderNumber(ancientDb, hash), fast.Config()), rawdb.ReadReceipts(archiveDb, hash, *rawdb.ReadHeaderNumber(archiveDb, hash), fast.Config()); types.DeriveSha(freceipts) != types.DeriveSha(areceipts) {
+		if freceipts, anreceipts, areceipts := rawdb.ReadReceipts(fastDb, hash, *rawdb.ReadHeaderNumber(fastDb, hash), fast.Config()), rawdb.ReadReceipts(ancientDb, hash, *rawdb.ReadHeaderNumber(ancientDb, hash), fast.Config()), rawdb.ReadReceipts(archiveDb, hash, *rawdb.ReadHeaderNumber(archiveDb, hash), fast.Config()); types.DeriveSha(freceipts, new(trie.Trie)) != types.DeriveSha(areceipts, new(trie.Trie)) {
 			t.Errorf("block #%d [%x]: receipts mismatch: fastdb %v, ancientdb %v, archivedb %v", num, hash, freceipts, anreceipts, areceipts)
 		}
 	}

@@ -23,6 +23,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 // BlockValidator is responsible for validating block headers, uncles and
@@ -61,7 +62,7 @@ func (v *BlockValidator) ValidateBody(block *types.Block) error {
 	if hash := types.CalcUncleHash(block.Uncles()); hash != header.UncleHash {
 		return fmt.Errorf("uncle root hash mismatch: have %x, want %x", hash, header.UncleHash)
 	}
-	if hash := types.DeriveSha(block.Transactions()); hash != header.TxHash {
+	if hash := types.DeriveSha(block.Transactions(), new(trie.Trie)); hash != header.TxHash {
 		return fmt.Errorf("transaction root hash mismatch: have %x, want %x", hash, header.TxHash)
 	}
 	if !v.bc.HasBlockAndState(block.ParentHash(), block.NumberU64()-1) {
@@ -89,7 +90,7 @@ func (v *BlockValidator) ValidateState(block *types.Block, statedb *state.StateD
 		return fmt.Errorf("invalid bloom (remote: %x  local: %x)", header.Bloom, rbloom)
 	}
 	// Tre receipt Trie's root (R = (Tr [[H1, R1], ... [Hn, R1]]))
-	receiptSha := types.DeriveSha(receipts)
+	receiptSha := types.DeriveSha(receipts, new(trie.Trie))
 	if receiptSha != header.ReceiptHash {
 		return fmt.Errorf("invalid receipt root hash (remote: %x local: %x)", header.ReceiptHash, receiptSha)
 	}

@@ -36,6 +36,7 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 //go:generate gencodec -type Genesis -field-override genesisSpecMarshaling -out gen_genesis.go
@@ -287,7 +288,7 @@ func (g *Genesis) ToBlock(db ethdb.Database) *types.Block {
 	statedb.Commit(false)
 	statedb.Database().TrieDB().Commit(root, true, nil)
 
-	return types.NewBlock(head, nil, nil, nil)
+	return types.NewBlock(head, nil, nil, nil, new(trie.Trie))
 }
 
 // Commit writes the block and state of a genesis specification to the database.

@@ -84,7 +84,7 @@ func TestBodyStorage(t *testing.T) {
 	WriteBody(db, hash, 0, body)
 	if entry := ReadBody(db, hash, 0); entry == nil {
 		t.Fatalf("Stored body not found")
-	} else if types.DeriveSha(types.Transactions(entry.Transactions)) != types.DeriveSha(types.Transactions(body.Transactions)) || types.CalcUncleHash(entry.Uncles) != types.CalcUncleHash(body.Uncles) {
+	} else if types.DeriveSha(types.Transactions(entry.Transactions), newHasher()) != types.DeriveSha(types.Transactions(body.Transactions), newHasher()) || types.CalcUncleHash(entry.Uncles) != types.CalcUncleHash(body.Uncles) {
 		t.Fatalf("Retrieved body mismatch: have %v, want %v", entry, body)
 	}
 	if entry := ReadBodyRLP(db, hash, 0); entry == nil {
@@ -138,7 +138,7 @@ func TestBlockStorage(t *testing.T) {
 	}
 	if entry := ReadBody(db, block.Hash(), block.NumberU64()); entry == nil {
 		t.Fatalf("Stored body not found")
-	} else if types.DeriveSha(types.Transactions(entry.Transactions)) != types.DeriveSha(block.Transactions()) || types.CalcUncleHash(entry.Uncles) != types.CalcUncleHash(block.Uncles()) {
+	} else if types.DeriveSha(types.Transactions(entry.Transactions), newHasher()) != types.DeriveSha(block.Transactions(), newHasher()) || types.CalcUncleHash(entry.Uncles) != types.CalcUncleHash(block.Uncles()) {
 		t.Fatalf("Retrieved body mismatch: have %v, want %v", entry, block.Body())
 	}
 	// Delete the block and verify the execution

@@ -18,6 +18,7 @@ package rawdb
 
 import (
 	"bytes"
+	"hash"
 	"math/big"
 	"testing"
 
@@ -26,8 +27,33 @@ import (
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
+	"golang.org/x/crypto/sha3"
 )
 
+// testHasher is the helper tool for transaction/receipt list hashing.
+// The original hasher is trie, in order to get rid of import cycle,
+// use the testing hasher instead.
+type testHasher struct {
+	hasher hash.Hash
+}
+
+func newHasher() *testHasher {
+	return &testHasher{hasher: sha3.NewLegacyKeccak256()}
+}
+
+func (h *testHasher) Reset() {
+	h.hasher.Reset()
+}
+
+func (h *testHasher) Update(key, val []byte) {
+	h.hasher.Write(key)
+	h.hasher.Write(val)
+}
+
+func (h *testHasher) Hash() common.Hash {
+	return common.BytesToHash(h.hasher.Sum(nil))
+}
+
 // Tests that positional lookup metadata can be stored and retrieved.
 func TestLookupStorage(t *testing.T) {
 	tests := []struct {
@@ -73,7 +99,7 @@ func TestLookupStorage(t *testing.T) {
 			tx3 := types.NewTransaction(3, common.BytesToAddress([]byte{0x33}), big.NewInt(333), 3333, big.NewInt(33333), []byte{0x33, 0x33, 0x33})
 			txs := []*types.Transaction{tx1, tx2, tx3}
 
-			block := types.NewBlock(&types.Header{Number: big.NewInt(314)}, txs, nil, nil)
+			block := types.NewBlock(&types.Header{Number: big.NewInt(314)}, txs, nil, nil, newHasher())
 
 			// Check that no transactions entries are in a pristine database
 			for i, tx := range txs {

@@ -79,20 +79,3 @@ func WriteChainConfig(db ethdb.KeyValueWriter, hash common.Hash, cfg *params.Cha
 		log.Crit("Failed to store chain config", "err", err)
 	}
 }
-
-// ReadPreimage retrieves a single preimage of the provided hash.
-func ReadPreimage(db ethdb.KeyValueReader, hash common.Hash) []byte {
-	data, _ := db.Get(preimageKey(hash))
-	return data
-}
-
-// WritePreimages writes the provided set of preimages to the database.
-func WritePreimages(db ethdb.KeyValueWriter, preimages map[common.Hash][]byte) {
-	for hash, preimage := range preimages {
-		if err := db.Put(preimageKey(hash), preimage); err != nil {
-			log.Crit("Failed to store trie preimage", "err", err)
-		}
-	}
-	preimageCounter.Inc(int64(len(preimages)))
-	preimageHitCounter.Inc(int64(len(preimages)))
-}

@@ -0,0 +1,96 @@
+// Copyright 2020 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 rawdb
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/log"
+)
+
+// ReadPreimage retrieves a single preimage of the provided hash.
+func ReadPreimage(db ethdb.KeyValueReader, hash common.Hash) []byte {
+	data, _ := db.Get(preimageKey(hash))
+	return data
+}
+
+// WritePreimages writes the provided set of preimages to the database.
+func WritePreimages(db ethdb.KeyValueWriter, preimages map[common.Hash][]byte) {
+	for hash, preimage := range preimages {
+		if err := db.Put(preimageKey(hash), preimage); err != nil {
+			log.Crit("Failed to store trie preimage", "err", err)
+		}
+	}
+	preimageCounter.Inc(int64(len(preimages)))
+	preimageHitCounter.Inc(int64(len(preimages)))
+}
+
+// ReadCode retrieves the contract code of the provided code hash.
+func ReadCode(db ethdb.KeyValueReader, hash common.Hash) []byte {
+	// Try with the legacy code scheme first, if not then try with current
+	// scheme. Since most of the code will be found with legacy scheme.
+	//
+	// todo(rjl493456442) change the order when we forcibly upgrade the code
+	// scheme with snapshot.
+	data, _ := db.Get(hash[:])
+	if len(data) != 0 {
+		return data
+	}
+	return ReadCodeWithPrefix(db, hash)
+}
+
+// ReadCodeWithPrefix retrieves the contract code of the provided code hash.
+// The main difference between this function and ReadCode is this function
+// will only check the existence with latest scheme(with prefix).
+func ReadCodeWithPrefix(db ethdb.KeyValueReader, hash common.Hash) []byte {
+	data, _ := db.Get(codeKey(hash))
+	return data
+}
+
+// WriteCode writes the provided contract code database.
+func WriteCode(db ethdb.KeyValueWriter, hash common.Hash, code []byte) {
+	if err := db.Put(codeKey(hash), code); err != nil {
+		log.Crit("Failed to store contract code", "err", err)
+	}
+}
+
+// DeleteCode deletes the specified contract code from the database.
+func DeleteCode(db ethdb.KeyValueWriter, hash common.Hash) {
+	if err := db.Delete(codeKey(hash)); err != nil {
+		log.Crit("Failed to delete contract code", "err", err)
+	}
+}
+
+// ReadTrieNode retrieves the trie node of the provided hash.
+func ReadTrieNode(db ethdb.KeyValueReader, hash common.Hash) []byte {
+	data, _ := db.Get(hash.Bytes())
+	return data
+}
+
+// WriteTrieNode writes the provided trie node database.
+func WriteTrieNode(db ethdb.KeyValueWriter, hash common.Hash, node []byte) {
+	if err := db.Put(hash.Bytes(), node); err != nil {
+		log.Crit("Failed to store trie node", "err", err)
+	}
+}
+
+// DeleteTrieNode deletes the specified trie node from the database.
+func DeleteTrieNode(db ethdb.KeyValueWriter, hash common.Hash) {
+	if err := db.Delete(hash.Bytes()); err != nil {
+		log.Crit("Failed to delete trie node", "err", err)
+	}
+}

@@ -34,11 +34,11 @@ func TestChainIterator(t *testing.T) {
 	var txs []*types.Transaction
 	for i := uint64(0); i <= 10; i++ {
 		if i == 0 {
-			block = types.NewBlock(&types.Header{Number: big.NewInt(int64(i))}, nil, nil, nil) // Empty genesis block
+			block = types.NewBlock(&types.Header{Number: big.NewInt(int64(i))}, nil, nil, nil, newHasher()) // Empty genesis block
 		} else {
 			tx := types.NewTransaction(i, common.BytesToAddress([]byte{0x11}), big.NewInt(111), 1111, big.NewInt(11111), []byte{0x11, 0x11, 0x11})
 			txs = append(txs, tx)
-			block = types.NewBlock(&types.Header{Number: big.NewInt(int64(i))}, []*types.Transaction{tx}, nil, nil)
+			block = types.NewBlock(&types.Header{Number: big.NewInt(int64(i))}, []*types.Transaction{tx}, nil, nil, newHasher())
 		}
 		WriteBlock(chainDb, block)
 		WriteCanonicalHash(chainDb, block.Hash(), block.NumberU64())

@@ -258,6 +258,7 @@ func InspectDatabase(db ethdb.Database) error {
 		numHashPairing  common.StorageSize
 		hashNumPairing  common.StorageSize
 		trieSize        common.StorageSize
+		codeSize        common.StorageSize
 		txlookupSize    common.StorageSize
 		accountSnapSize common.StorageSize
 		storageSnapSize common.StorageSize
@@ -316,6 +317,8 @@ func InspectDatabase(db ethdb.Database) error {
 			chtTrieNodes += size
 		case bytes.HasPrefix(key, []byte("blt-")) && len(key) == 4+common.HashLength:
 			bloomTrieNodes += size
+		case bytes.HasPrefix(key, codePrefix) && len(key) == len(codePrefix)+common.HashLength:
+			codeSize += size
 		case len(key) == common.HashLength:
 			trieSize += size
 		default:
@@ -355,6 +358,7 @@ func InspectDatabase(db ethdb.Database) error {
 		{"Key-Value store", "Block hash->number", hashNumPairing.String()},
 		{"Key-Value store", "Transaction index", txlookupSize.String()},
 		{"Key-Value store", "Bloombit index", bloomBitsSize.String()},
+		{"Key-Value store", "Contract codes", codeSize.String()},
 		{"Key-Value store", "Trie nodes", trieSize.String()},
 		{"Key-Value store", "Trie preimages", preimageSize.String()},
 		{"Key-Value store", "Account snapshot", accountSnapSize.String()},

@@ -18,6 +18,7 @@
 package rawdb
 
 import (
+	"bytes"
 	"encoding/binary"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -69,6 +70,7 @@ var (
 	bloomBitsPrefix       = []byte("B") // bloomBitsPrefix + bit (uint16 big endian) + section (uint64 big endian) + hash -> bloom bits
 	SnapshotAccountPrefix = []byte("a") // SnapshotAccountPrefix + account hash -> account trie value
 	SnapshotStoragePrefix = []byte("o") // SnapshotStoragePrefix + account hash + storage hash -> storage trie value
+	codePrefix            = []byte("c") // codePrefix + code hash -> account code
 
 	preimagePrefix = []byte("secure-key-")      // preimagePrefix + hash -> preimage
 	configPrefix   = []byte("ethereum-config-") // config prefix for the db
@@ -192,6 +194,20 @@ func preimageKey(hash common.Hash) []byte {
 	return append(preimagePrefix, hash.Bytes()...)
 }
 
+// codeKey = codePrefix + hash
+func codeKey(hash common.Hash) []byte {
+	return append(codePrefix, hash.Bytes()...)
+}
+
+// IsCodeKey reports whether the given byte slice is the key of contract code,
+// if so return the raw code hash as well.
+func IsCodeKey(key []byte) (bool, []byte) {
+	if bytes.HasPrefix(key, codePrefix) && len(key) == common.HashLength+len(codePrefix) {
+		return true, key[len(codePrefix):]
+	}
+	return false, nil
+}
+
 // configKey = configPrefix + hash
 func configKey(hash common.Hash) []byte {
 	return append(configPrefix, hash.Bytes()...)

@@ -17,9 +17,12 @@
 package state
 
 import (
+	"errors"
 	"fmt"
 
+	"github.com/VictoriaMetrics/fastcache"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/trie"
 	lru "github.com/hashicorp/golang-lru"
@@ -28,6 +31,9 @@ import (
 const (
 	// Number of codehash->size associations to keep.
 	codeSizeCacheSize = 100000
+
+	// Cache size granted for caching clean code.
+	codeCacheSize = 64 * 1024 * 1024
 )
 
 // Database wraps access to tries and contract code.
@@ -111,12 +117,14 @@ func NewDatabaseWithCache(db ethdb.Database, cache int, journal string) Database
 	return &cachingDB{
 		db:            trie.NewDatabaseWithCache(db, cache, journal),
 		codeSizeCache: csc,
+		codeCache:     fastcache.New(codeCacheSize),
 	}
 }
 
 type cachingDB struct {
 	db            *trie.Database
 	codeSizeCache *lru.Cache
+	codeCache     *fastcache.Cache
 }
 
 // OpenTrie opens the main account trie at a specific root hash.
@@ -141,11 +149,32 @@ func (db *cachingDB) CopyTrie(t Trie) Trie {
 
 // ContractCode retrieves a particular contract's code.
 func (db *cachingDB) ContractCode(addrHash, codeHash common.Hash) ([]byte, error) {
-	code, err := db.db.Node(codeHash)
-	if err == nil {
+	if code := db.codeCache.Get(nil, codeHash.Bytes()); len(code) > 0 {
+		return code, nil
+	}
+	code := rawdb.ReadCode(db.db.DiskDB(), codeHash)
+	if len(code) > 0 {
+		db.codeCache.Set(codeHash.Bytes(), code)
+		db.codeSizeCache.Add(codeHash, len(code))
+		return code, nil
+	}
+	return nil, errors.New("not found")
+}
+
+// ContractCodeWithPrefix retrieves a particular contract's code. If the
+// code can't be found in the cache, then check the existence with **new**
+// db scheme.
+func (db *cachingDB) ContractCodeWithPrefix(addrHash, codeHash common.Hash) ([]byte, error) {
+	if code := db.codeCache.Get(nil, codeHash.Bytes()); len(code) > 0 {
+		return code, nil
+	}
+	code := rawdb.ReadCodeWithPrefix(db.db.DiskDB(), codeHash)
+	if len(code) > 0 {
+		db.codeCache.Set(codeHash.Bytes(), code)
 		db.codeSizeCache.Add(codeHash, len(code))
+		return code, nil
 	}
-	return code, err
+	return nil, errors.New("not found")
 }
 
 // ContractCodeSize retrieves a particular contracts code's size.

@@ -28,6 +28,7 @@ import (
 func TestNodeIteratorCoverage(t *testing.T) {
 	// Create some arbitrary test state to iterate
 	db, root, _ := makeTestState()
+	db.TrieDB().Commit(root, false, nil)
 
 	state, err := New(root, db, nil)
 	if err != nil {
@@ -42,7 +43,10 @@ func TestNodeIteratorCoverage(t *testing.T) {
 	}
 	// Cross check the iterated hashes and the database/nodepool content
 	for hash := range hashes {
-		if _, err := db.TrieDB().Node(hash); err != nil {
+		if _, err = db.TrieDB().Node(hash); err != nil {
+			_, err = db.ContractCode(common.Hash{}, hash)
+		}
+		if err != nil {
 			t.Errorf("failed to retrieve reported node %x", hash)
 		}
 	}

@@ -25,6 +25,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/state/snapshot"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
@@ -42,9 +43,6 @@ type revision struct {
 var (
 	// emptyRoot is the known root hash of an empty trie.
 	emptyRoot = common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
-
-	// emptyCode is the known hash of the empty EVM bytecode.
-	emptyCode = crypto.Keccak256Hash(nil)
 )
 
 type proofList [][]byte
@@ -589,7 +587,10 @@ func (s *StateDB) createObject(addr common.Address) (newobj, prev *stateObject)
 		s.journal.append(resetObjectChange{prev: prev, prevdestruct: prevdestruct})
 	}
 	s.setStateObject(newobj)
-	return newobj, prev
+	if prev != nil && !prev.deleted {
+		return newobj, prev
+	}
+	return newobj, nil
 }
 
 // CreateAccount explicitly creates a state object. If a state object with the address
@@ -816,11 +817,12 @@ func (s *StateDB) Commit(deleteEmptyObjects bool) (common.Hash, error) {
 	s.IntermediateRoot(deleteEmptyObjects)
 
 	// Commit objects to the trie, measuring the elapsed time
+	codeWriter := s.db.TrieDB().DiskDB().NewBatch()
 	for addr := range s.stateObjectsDirty {
 		if obj := s.stateObjects[addr]; !obj.deleted {
 			// Write any contract code associated with the state object
 			if obj.code != nil && obj.dirtyCode {
-				s.db.TrieDB().InsertBlob(common.BytesToHash(obj.CodeHash()), obj.code)
+				rawdb.WriteCode(codeWriter, common.BytesToHash(obj.CodeHash()), obj.code)
 				obj.dirtyCode = false
 			}
 			// Write any storage changes in the state object to its storage trie
@@ -832,6 +834,11 @@ func (s *StateDB) Commit(deleteEmptyObjects bool) (common.Hash, error) {
 	if len(s.stateObjectsDirty) > 0 {
 		s.stateObjectsDirty = make(map[common.Address]struct{})
 	}
+	if codeWriter.ValueSize() > 0 {
+		if err := codeWriter.Write(); err != nil {
+			log.Crit("Failed to commit dirty codes", "error", err)
+		}
+	}
 	// Write the account trie changes, measuing the amount of wasted time
 	var start time.Time
 	if metrics.EnabledExpensive {
@@ -847,10 +854,6 @@ func (s *StateDB) Commit(deleteEmptyObjects bool) (common.Hash, error) {
 		if account.Root != emptyRoot {
 			s.db.TrieDB().Reference(account.Root, parent)
 		}
-		code := common.BytesToHash(account.CodeHash)
-		if code != emptyCode {
-			s.db.TrieDB().Reference(code, parent)
-		}
 		return nil
 	})
 	if metrics.EnabledExpensive {

@@ -34,7 +34,7 @@ func NewStateSync(root common.Hash, database ethdb.KeyValueReader, bloom *trie.S
 			return err
 		}
 		syncer.AddSubTrie(obj.Root, 64, parent, nil)
-		syncer.AddRawEntry(common.BytesToHash(obj.CodeHash), 64, parent)
+		syncer.AddCodeEntry(common.BytesToHash(obj.CodeHash), 64, parent)
 		return nil
 	}
 	syncer = trie.NewSync(root, database, callback, bloom)

@@ -133,13 +133,17 @@ func TestEmptyStateSync(t *testing.T) {
 
 // Tests that given a root hash, a state can sync iteratively on a single thread,
 // requesting retrieval tasks and returning all of them in one go.
-func TestIterativeStateSyncIndividual(t *testing.T) { testIterativeStateSync(t, 1) }
-func TestIterativeStateSyncBatched(t *testing.T)    { testIterativeStateSync(t, 100) }
+func TestIterativeStateSyncIndividual(t *testing.T)         { testIterativeStateSync(t, 1, false) }
+func TestIterativeStateSyncBatched(t *testing.T)            { testIterativeStateSync(t, 100, false) }
+func TestIterativeStateSyncIndividualFromDisk(t *testing.T) { testIterativeStateSync(t, 1, true) }
+func TestIterativeStateSyncBatchedFromDisk(t *testing.T)    { testIterativeStateSync(t, 100, true) }
 
-func testIterativeStateSync(t *testing.T, count int) {
+func testIterativeStateSync(t *testing.T, count int, commit bool) {
 	// Create a random state to copy
 	srcDb, srcRoot, srcAccounts := makeTestState()
-
+	if commit {
+		srcDb.TrieDB().Commit(srcRoot, false, nil)
+	}
 	// Create a destination state and sync with the scheduler
 	dstDb := rawdb.NewMemoryDatabase()
 	sched := NewStateSync(srcRoot, dstDb, trie.NewSyncBloom(1, dstDb))
@@ -149,13 +153,18 @@ func testIterativeStateSync(t *testing.T, count int) {
 		results := make([]trie.SyncResult, len(queue))
 		for i, hash := range queue {
 			data, err := srcDb.TrieDB().Node(hash)
+			if err != nil {
+				data, err = srcDb.ContractCode(common.Hash{}, hash)
+			}
 			if err != nil {
 				t.Fatalf("failed to retrieve node data for %x", hash)
 			}
 			results[i] = trie.SyncResult{Hash: hash, Data: data}
 		}
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := dstDb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -184,13 +193,18 @@ func TestIterativeDelayedStateSync(t *testing.T) {
 		results := make([]trie.SyncResult, len(queue)/2+1)
 		for i, hash := range queue[:len(results)] {
 			data, err := srcDb.TrieDB().Node(hash)
+			if err != nil {
+				data, err = srcDb.ContractCode(common.Hash{}, hash)
+			}
 			if err != nil {
 				t.Fatalf("failed to retrieve node data for %x", hash)
 			}
 			results[i] = trie.SyncResult{Hash: hash, Data: data}
 		}
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := dstDb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -226,14 +240,19 @@ func testIterativeRandomStateSync(t *testing.T, count int) {
 		results := make([]trie.SyncResult, 0, len(queue))
 		for hash := range queue {
 			data, err := srcDb.TrieDB().Node(hash)
+			if err != nil {
+				data, err = srcDb.ContractCode(common.Hash{}, hash)
+			}
 			if err != nil {
 				t.Fatalf("failed to retrieve node data for %x", hash)
 			}
 			results = append(results, trie.SyncResult{Hash: hash, Data: data})
 		}
 		// Feed the retrieved results back and queue new tasks
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := dstDb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -270,6 +289,9 @@ func TestIterativeRandomDelayedStateSync(t *testing.T) {
 			delete(queue, hash)
 
 			data, err := srcDb.TrieDB().Node(hash)
+			if err != nil {
+				data, err = srcDb.ContractCode(common.Hash{}, hash)
+			}
 			if err != nil {
 				t.Fatalf("failed to retrieve node data for %x", hash)
 			}
@@ -280,8 +302,10 @@ func TestIterativeRandomDelayedStateSync(t *testing.T) {
 			}
 		}
 		// Feed the retrieved results back and queue new tasks
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := dstDb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -302,6 +326,15 @@ func TestIncompleteStateSync(t *testing.T) {
 	// Create a random state to copy
 	srcDb, srcRoot, srcAccounts := makeTestState()
 
+	// isCode reports whether the hash is contract code hash.
+	isCode := func(hash common.Hash) bool {
+		for _, acc := range srcAccounts {
+			if hash == crypto.Keccak256Hash(acc.code) {
+				return true
+			}
+		}
+		return false
+	}
 	checkTrieConsistency(srcDb.TrieDB().DiskDB().(ethdb.Database), srcRoot)
 
 	// Create a destination state and sync with the scheduler
@@ -315,14 +348,19 @@ func TestIncompleteStateSync(t *testing.T) {
 		results := make([]trie.SyncResult, len(queue))
 		for i, hash := range queue {
 			data, err := srcDb.TrieDB().Node(hash)
+			if err != nil {
+				data, err = srcDb.ContractCode(common.Hash{}, hash)
+			}
 			if err != nil {
 				t.Fatalf("failed to retrieve node data for %x", hash)
 			}
 			results[i] = trie.SyncResult{Hash: hash, Data: data}
 		}
 		// Process each of the state nodes
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := dstDb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -333,12 +371,9 @@ func TestIncompleteStateSync(t *testing.T) {
 			added = append(added, result.Hash)
 		}
 		// Check that all known sub-tries added so far are complete or missing entirely.
-	checkSubtries:
 		for _, hash := range added {
-			for _, acc := range srcAccounts {
-				if hash == crypto.Keccak256Hash(acc.code) {
-					continue checkSubtries // skip trie check of code nodes.
-				}
+			if isCode(hash) {
+				continue
 			}
 			// Can't use checkStateConsistency here because subtrie keys may have odd
 			// length and crash in LeafKey.
@@ -351,13 +386,25 @@ func TestIncompleteStateSync(t *testing.T) {
 	}
 	// Sanity check that removing any node from the database is detected
 	for _, node := range added[1:] {
-		key := node.Bytes()
-		value, _ := dstDb.Get(key)
-
-		dstDb.Delete(key)
+		var (
+			key  = node.Bytes()
+			code = isCode(node)
+			val  []byte
+		)
+		if code {
+			val = rawdb.ReadCode(dstDb, node)
+			rawdb.DeleteCode(dstDb, node)
+		} else {
+			val = rawdb.ReadTrieNode(dstDb, node)
+			rawdb.DeleteTrieNode(dstDb, node)
+		}
 		if err := checkStateConsistency(dstDb, added[0]); err == nil {
 			t.Fatalf("trie inconsistency not caught, missing: %x", key)
 		}
-		dstDb.Put(key, value)
+		if code {
+			rawdb.WriteCode(dstDb, node, val)
+		} else {
+			rawdb.WriteTrieNode(dstDb, node, val)
+		}
 	}
 }

@@ -34,6 +34,7 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 // testTxPoolConfig is a transaction pool configuration without stateful disk
@@ -54,7 +55,7 @@ type testBlockChain struct {
 func (bc *testBlockChain) CurrentBlock() *types.Block {
 	return types.NewBlock(&types.Header{
 		GasLimit: bc.gasLimit,
-	}, nil, nil, nil)
+	}, nil, nil, nil, new(trie.Trie))
 }
 
 func (bc *testBlockChain) GetBlock(hash common.Hash, number uint64) *types.Block {

@@ -35,7 +35,7 @@ import (
 )
 
 var (
-	EmptyRootHash  = DeriveSha(Transactions{})
+	EmptyRootHash  = common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
 	EmptyUncleHash = rlpHash([]*Header(nil))
 )
 
@@ -221,22 +221,22 @@ type storageblock struct {
 // The values of TxHash, UncleHash, ReceiptHash and Bloom in header
 // are ignored and set to values derived from the given txs, uncles
 // and receipts.
-func NewBlock(header *Header, txs []*Transaction, uncles []*Header, receipts []*Receipt) *Block {
+func NewBlock(header *Header, txs []*Transaction, uncles []*Header, receipts []*Receipt, hasher Hasher) *Block {
 	b := &Block{header: CopyHeader(header), td: new(big.Int)}
 
 	// TODO: panic if len(txs) != len(receipts)
 	if len(txs) == 0 {
 		b.header.TxHash = EmptyRootHash
 	} else {
-		b.header.TxHash = DeriveSha(Transactions(txs))
+		b.header.TxHash = DeriveSha(Transactions(txs), hasher)
 		b.transactions = make(Transactions, len(txs))
 		copy(b.transactions, txs)
 	}
 
 	if len(receipts) == 0 {
 		b.header.ReceiptHash = EmptyRootHash
 	} else {
-		b.header.ReceiptHash = DeriveSha(Receipts(receipts))
+		b.header.ReceiptHash = DeriveSha(Receipts(receipts), hasher)
 		b.header.Bloom = CreateBloom(receipts)
 	}
 

@@ -18,6 +18,7 @@ package types
 
 import (
 	"bytes"
+	"hash"
 	"math/big"
 	"reflect"
 	"testing"
@@ -27,6 +28,7 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
+	"golang.org/x/crypto/sha3"
 )
 
 // from bcValidBlockTest.json, "SimpleTx"
@@ -90,6 +92,30 @@ func BenchmarkEncodeBlock(b *testing.B) {
 	}
 }
 
+// testHasher is the helper tool for transaction/receipt list hashing.
+// The original hasher is trie, in order to get rid of import cycle,
+// use the testing hasher instead.
+type testHasher struct {
+	hasher hash.Hash
+}
+
+func newHasher() *testHasher {
+	return &testHasher{hasher: sha3.NewLegacyKeccak256()}
+}
+
+func (h *testHasher) Reset() {
+	h.hasher.Reset()
+}
+
+func (h *testHasher) Update(key, val []byte) {
+	h.hasher.Write(key)
+	h.hasher.Write(val)
+}
+
+func (h *testHasher) Hash() common.Hash {
+	return common.BytesToHash(h.hasher.Sum(nil))
+}
+
 func makeBenchBlock() *Block {
 	var (
 		key, _   = crypto.GenerateKey()
@@ -128,5 +154,5 @@ func makeBenchBlock() *Block {
 			Extra:      []byte("benchmark uncle"),
 		}
 	}
-	return NewBlock(header, txs, uncles, receipts)
+	return NewBlock(header, txs, uncles, receipts, newHasher())
 }

@@ -21,21 +21,28 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/rlp"
-	"github.com/ethereum/go-ethereum/trie"
 )
 
+// DerivableList is the interface which can derive the hash.
 type DerivableList interface {
 	Len() int
 	GetRlp(i int) []byte
 }
 
-func DeriveSha(list DerivableList) common.Hash {
+// Hasher is the tool used to calculate the hash of derivable list.
+type Hasher interface {
+	Reset()
+	Update([]byte, []byte)
+	Hash() common.Hash
+}
+
+func DeriveSha(list DerivableList, hasher Hasher) common.Hash {
+	hasher.Reset()
 	keybuf := new(bytes.Buffer)
-	trie := new(trie.Trie)
 	for i := 0; i < list.Len(); i++ {
 		keybuf.Reset()
 		rlp.Encode(keybuf, uint(i))
-		trie.Update(keybuf.Bytes(), list.GetRlp(i))
+		hasher.Update(keybuf.Bytes(), list.GetRlp(i))
 	}
-	return trie.Hash()
+	return hasher.Hash()
 }

@@ -109,7 +109,7 @@ type Downloader struct {
 	peers      *peerSet // Set of active peers from which download can proceed
 
 	stateDB    ethdb.Database  // Database to state sync into (and deduplicate via)
-	stateBloom *trie.SyncBloom // Bloom filter for fast trie node existence checks
+	stateBloom *trie.SyncBloom // Bloom filter for fast trie node and contract code existence checks
 
 	// Statistics
 	syncStatsChainOrigin uint64 // Origin block number where syncing started at

@@ -31,6 +31,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/metrics"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 const (
@@ -771,7 +772,7 @@ func (q *queue) DeliverBodies(id string, txLists [][]*types.Transaction, uncleLi
 	q.lock.Lock()
 	defer q.lock.Unlock()
 	validate := func(index int, header *types.Header) error {
-		if types.DeriveSha(types.Transactions(txLists[index])) != header.TxHash {
+		if types.DeriveSha(types.Transactions(txLists[index]), new(trie.Trie)) != header.TxHash {
 			return errInvalidBody
 		}
 		if types.CalcUncleHash(uncleLists[index]) != header.UncleHash {
@@ -796,7 +797,7 @@ func (q *queue) DeliverReceipts(id string, receiptList [][]*types.Receipt) (int,
 	q.lock.Lock()
 	defer q.lock.Unlock()
 	validate := func(index int, header *types.Header) error {
-		if types.DeriveSha(types.Receipts(receiptList[index])) != header.ReceiptHash {
+		if types.DeriveSha(types.Receipts(receiptList[index]), new(trie.Trie)) != header.ReceiptHash {
 			return errInvalidReceipt
 		}
 		return nil

@@ -474,7 +474,7 @@ func (s *stateSync) process(req *stateReq) (int, error) {
 
 	// Iterate over all the delivered data and inject one-by-one into the trie
 	for _, blob := range req.response {
-		_, hash, err := s.processNodeData(blob)
+		hash, err := s.processNodeData(blob)
 		switch err {
 		case nil:
 			s.numUncommitted++
@@ -512,13 +512,13 @@ func (s *stateSync) process(req *stateReq) (int, error) {
 // processNodeData tries to inject a trie node data blob delivered from a remote
 // peer into the state trie, returning whether anything useful was written or any
 // error occurred.
-func (s *stateSync) processNodeData(blob []byte) (bool, common.Hash, error) {
+func (s *stateSync) processNodeData(blob []byte) (common.Hash, error) {
 	res := trie.SyncResult{Data: blob}
 	s.keccak.Reset()
 	s.keccak.Write(blob)
 	s.keccak.Sum(res.Hash[:0])
-	committed, _, err := s.sched.Process([]trie.SyncResult{res})
-	return committed, res.Hash, err
+	err := s.sched.Process(res)
+	return res.Hash, err
 }
 
 // updateStats bumps the various state sync progress counters and displays a log

@@ -28,6 +28,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/metrics"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 const (
@@ -540,7 +541,7 @@ func (f *BlockFetcher) loop() {
 						announce.time = task.time
 
 						// If the block is empty (header only), short circuit into the final import queue
-						if header.TxHash == types.DeriveSha(types.Transactions{}) && header.UncleHash == types.CalcUncleHash([]*types.Header{}) {
+						if header.TxHash == types.EmptyRootHash && header.UncleHash == types.EmptyUncleHash {
 							log.Trace("Block empty, skipping body retrieval", "peer", announce.origin, "number", header.Number, "hash", header.Hash())
 
 							block := types.NewBlockWithHeader(header)
@@ -619,7 +620,7 @@ func (f *BlockFetcher) loop() {
 							continue
 						}
 						if txnHash == (common.Hash{}) {
-							txnHash = types.DeriveSha(types.Transactions(task.transactions[i]))
+							txnHash = types.DeriveSha(types.Transactions(task.transactions[i]), new(trie.Trie))
 						}
 						if txnHash != announce.header.TxHash {
 							continue

@@ -31,14 +31,15 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 var (
 	testdb       = rawdb.NewMemoryDatabase()
 	testKey, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 	testAddress  = crypto.PubkeyToAddress(testKey.PublicKey)
 	genesis      = core.GenesisBlockForTesting(testdb, testAddress, big.NewInt(1000000000))
-	unknownBlock = types.NewBlock(&types.Header{GasLimit: params.GenesisGasLimit}, nil, nil, nil)
+	unknownBlock = types.NewBlock(&types.Header{GasLimit: params.GenesisGasLimit}, nil, nil, nil, new(trie.Trie))
 )
 
 // makeChain creates a chain of n blocks starting at and including parent.

@@ -608,7 +608,14 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 				return errResp(ErrDecode, "msg %v: %v", msg, err)
 			}
 			// Retrieve the requested state entry, stopping if enough was found
-			if entry, err := pm.blockchain.TrieNode(hash); err == nil {
+			// todo now the code and trienode is mixed in the protocol level,
+			// separate these two types.
+			entry, err := pm.blockchain.TrieNode(hash)
+			if len(entry) == 0 || err != nil {
+				// Read the contract code with prefix only to save unnecessary lookups.
+				entry, err = pm.blockchain.ContractCodeWithPrefix(hash)
+			}
+			if err == nil && len(entry) > 0 {
 				data = append(data, entry)
 				bytes += len(entry)
 			}
@@ -703,7 +710,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 			log.Warn("Propagated block has invalid uncles", "have", hash, "exp", request.Block.UncleHash())
 			break // TODO(karalabe): return error eventually, but wait a few releases
 		}
-		if hash := types.DeriveSha(request.Block.Transactions()); hash != request.Block.TxHash() {
+		if hash := types.DeriveSha(request.Block.Transactions(), new(trie.Trie)); hash != request.Block.TxHash() {
 			log.Warn("Propagated block has invalid body", "have", hash, "exp", request.Block.TxHash())
 			break // TODO(karalabe): return error eventually, but wait a few releases
 		}

@@ -116,7 +116,7 @@ func (r *BlockRequest) Validate(db ethdb.Database, msg *Msg) error {
 	if r.Header == nil {
 		return errHeaderUnavailable
 	}
-	if r.Header.TxHash != types.DeriveSha(types.Transactions(body.Transactions)) {
+	if r.Header.TxHash != types.DeriveSha(types.Transactions(body.Transactions), new(trie.Trie)) {
 		return errTxHashMismatch
 	}
 	if r.Header.UncleHash != types.CalcUncleHash(body.Uncles) {
@@ -174,7 +174,7 @@ func (r *ReceiptsRequest) Validate(db ethdb.Database, msg *Msg) error {
 	if r.Header == nil {
 		return errHeaderUnavailable
 	}
-	if r.Header.ReceiptHash != types.DeriveSha(receipt) {
+	if r.Header.ReceiptHash != types.DeriveSha(receipt, new(trie.Trie)) {
 		return errReceiptHashMismatch
 	}
 	// Validations passed, store and return

@@ -489,7 +489,7 @@ func (h *serverHandler) handleMsg(p *clientPeer, wg *sync.WaitGroup) error {
 						p.bumpInvalid()
 						continue
 					}
-					code, err := triedb.Node(common.BytesToHash(account.CodeHash))
+					code, err := h.blockchain.StateCache().ContractCode(common.BytesToHash(request.AccKey), common.BytesToHash(account.CodeHash))
 					if err != nil {
 						p.Log().Warn("Failed to retrieve account code", "block", header.Number, "hash", header.Hash(), "account", common.BytesToHash(request.AccKey), "codehash", common.BytesToHash(account.CodeHash), "err", err)
 						continue

@@ -101,7 +101,7 @@ type CodeRequest struct {
 
 // StoreResult stores the retrieved data in local database
 func (req *CodeRequest) StoreResult(db ethdb.Database) {
-	db.Put(req.Hash[:], req.Data)
+	rawdb.WriteCode(db, req.Hash, req.Data)
 }
 
 // BlockRequest is the ODR request type for retrieving block bodies

@@ -87,7 +87,7 @@ func (odr *testOdr) Retrieve(ctx context.Context, req OdrRequest) error {
 		t.Prove(req.Key, 0, nodes)
 		req.Proof = nodes
 	case *CodeRequest:
-		req.Data, _ = odr.sdb.Get(req.Hash[:])
+		req.Data = rawdb.ReadCode(odr.sdb, req.Hash)
 	}
 	req.StoreResult(odr.ldb)
 	return nil

@@ -22,6 +22,7 @@ import (
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
@@ -70,7 +71,8 @@ func (db *odrDatabase) ContractCode(addrHash, codeHash common.Hash) ([]byte, err
 	if codeHash == sha3Nil {
 		return nil, nil
 	}
-	if code, err := db.backend.Database().Get(codeHash[:]); err == nil {
+	code := rawdb.ReadCode(db.backend.Database(), codeHash)
+	if len(code) != 0 {
 		return code, nil
 	}
 	id := *db.id

@@ -34,6 +34,7 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 const (
@@ -711,6 +712,7 @@ func (w *worker) updateSnapshot() {
 		w.current.txs,
 		uncles,
 		w.current.receipts,
+		new(trie.Trie),
 	)
 
 	w.snapshotState = w.current.state.Copy()

@@ -27,6 +27,7 @@ import (
 
 	"github.com/VictoriaMetrics/fastcache"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/metrics"
@@ -57,15 +58,6 @@ var (
 	memcacheCommitSizeMeter  = metrics.NewRegisteredMeter("trie/memcache/commit/size", nil)
 )
 
-// secureKeyPrefix is the database key prefix used to store trie node preimages.
-var secureKeyPrefix = []byte("secure-key-")
-
-// secureKeyPrefixLength is the length of the above prefix
-const secureKeyPrefixLength = 11
-
-// secureKeyLength is the length of the above prefix + 32byte hash.
-const secureKeyLength = secureKeyPrefixLength + 32
-
 // Database is an intermediate write layer between the trie data structures and
 // the disk database. The aim is to accumulate trie writes in-memory and only
 // periodically flush a couple tries to disk, garbage collecting the remainder.
@@ -78,7 +70,7 @@ type Database struct {
 	diskdb ethdb.KeyValueStore // Persistent storage for matured trie nodes
 
 	cleans  *fastcache.Cache            // GC friendly memory cache of clean node RLPs
-	dirties map[common.Hash]*cachedNode // Data and references relationships of dirty nodes
+	dirties map[common.Hash]*cachedNode // Data and references relationships of dirty trie nodes
 	oldest  common.Hash                 // Oldest tracked node, flush-list head
 	newest  common.Hash                 // Newest tracked node, flush-list tail
 
@@ -139,8 +131,8 @@ type rawShortNode struct {
 func (n rawShortNode) cache() (hashNode, bool)   { panic("this should never end up in a live trie") }
 func (n rawShortNode) fstring(ind string) string { panic("this should never end up in a live trie") }
 
-// cachedNode is all the information we know about a single cached node in the
-// memory database write layer.
+// cachedNode is all the information we know about a single cached trie node
+// in the memory database write layer.
 type cachedNode struct {
 	node node   // Cached collapsed trie node, or raw rlp data
 	size uint16 // Byte size of the useful cached data
@@ -161,8 +153,8 @@ var cachedNodeSize = int(reflect.TypeOf(cachedNode{}).Size())
 // reference map.
 const cachedNodeChildrenSize = 48
 
-// rlp returns the raw rlp encoded blob of the cached node, either directly from
-// the cache, or by regenerating it from the collapsed node.
+// rlp returns the raw rlp encoded blob of the cached trie node, either directly
+// from the cache, or by regenerating it from the collapsed node.
 func (n *cachedNode) rlp() []byte {
 	if node, ok := n.node.(rawNode); ok {
 		return node
@@ -183,9 +175,9 @@ func (n *cachedNode) obj(hash common.Hash) node {
 	return expandNode(hash[:], n.node)
 }
 
-// forChilds invokes the callback for  all the tracked children of this node,
-// both the implicit ones  from inside the node as well as the explicit ones
-//from outside the node.
+// forChilds invokes the callback for all the tracked children of this node,
+// both the implicit ones from inside the node as well as the explicit ones
+// from outside the node.
 func (n *cachedNode) forChilds(onChild func(hash common.Hash)) {
 	for child := range n.children {
 		onChild(child)
@@ -305,25 +297,14 @@ func NewDatabaseWithCache(diskdb ethdb.KeyValueStore, cache int, journal string)
 }
 
 // DiskDB retrieves the persistent storage backing the trie database.
-func (db *Database) DiskDB() ethdb.KeyValueReader {
+func (db *Database) DiskDB() ethdb.KeyValueStore {
 	return db.diskdb
 }
 
-// InsertBlob writes a new reference tracked blob to the memory database if it's
-// yet unknown. This method should only be used for non-trie nodes that require
-// reference counting, since trie nodes are garbage collected directly through
-// their embedded children.
-func (db *Database) InsertBlob(hash common.Hash, blob []byte) {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
-	db.insert(hash, len(blob), rawNode(blob))
-}
-
-// insert inserts a collapsed trie node into the memory database. This method is
-// a more generic version of InsertBlob, supporting both raw blob insertions as
-// well ex trie node insertions. The blob size must be specified to allow proper
-// size tracking.
+// insert inserts a collapsed trie node into the memory database.
+// The blob size must be specified to allow proper size tracking.
+// All nodes inserted by this function will be reference tracked
+// and in theory should only used for **trie nodes** insertion.
 func (db *Database) insert(hash common.Hash, size int, node node) {
 	// If the node's already cached, skip
 	if _, ok := db.dirties[hash]; ok {
@@ -430,39 +411,30 @@ func (db *Database) Node(hash common.Hash) ([]byte, error) {
 	memcacheDirtyMissMeter.Mark(1)
 
 	// Content unavailable in memory, attempt to retrieve from disk
-	enc, err := db.diskdb.Get(hash[:])
-	if err == nil && enc != nil {
+	enc := rawdb.ReadTrieNode(db.diskdb, hash)
+	if len(enc) != 0 {
 		if db.cleans != nil {
 			db.cleans.Set(hash[:], enc)
 			memcacheCleanMissMeter.Mark(1)
 			memcacheCleanWriteMeter.Mark(int64(len(enc)))
 		}
+		return enc, nil
 	}
-	return enc, err
+	return nil, errors.New("not found")
 }
 
 // preimage retrieves a cached trie node pre-image from memory. If it cannot be
 // found cached, the method queries the persistent database for the content.
-func (db *Database) preimage(hash common.Hash) ([]byte, error) {
+func (db *Database) preimage(hash common.Hash) []byte {
 	// Retrieve the node from cache if available
 	db.lock.RLock()
 	preimage := db.preimages[hash]
 	db.lock.RUnlock()
 
 	if preimage != nil {
-		return preimage, nil
+		return preimage
 	}
-	// Content unavailable in memory, attempt to retrieve from disk
-	return db.diskdb.Get(secureKey(hash))
-}
-
-// secureKey returns the database key for the preimage of key (as a newly
-// allocated byte-slice)
-func secureKey(hash common.Hash) []byte {
-	buf := make([]byte, secureKeyLength)
-	copy(buf, secureKeyPrefix)
-	copy(buf[secureKeyPrefixLength:], hash[:])
-	return buf
+	return rawdb.ReadPreimage(db.diskdb, hash)
 }
 
 // Nodes retrieves the hashes of all the nodes cached within the memory database.
@@ -482,6 +454,9 @@ func (db *Database) Nodes() []common.Hash {
 }
 
 // Reference adds a new reference from a parent node to a child node.
+// This function is used to add reference between internal trie node
+// and external node(e.g. storage trie root), all internal trie nodes
+// are referenced together by database itself.
 func (db *Database) Reference(child common.Hash, parent common.Hash) {
 	db.lock.Lock()
 	defer db.lock.Unlock()
@@ -604,37 +579,25 @@ func (db *Database) Cap(limit common.StorageSize) error {
 	size := db.dirtiesSize + common.StorageSize((len(db.dirties)-1)*cachedNodeSize)
 	size += db.childrenSize - common.StorageSize(len(db.dirties[common.Hash{}].children)*(common.HashLength+2))
 
-	// We reuse an ephemeral buffer for the keys. The batch Put operation
-	// copies it internally, so we can reuse it.
-	var keyBuf [secureKeyLength]byte
-	copy(keyBuf[:], secureKeyPrefix)
-
 	// If the preimage cache got large enough, push to disk. If it's still small
 	// leave for later to deduplicate writes.
 	flushPreimages := db.preimagesSize > 4*1024*1024
 	if flushPreimages {
-		for hash, preimage := range db.preimages {
-			copy(keyBuf[secureKeyPrefixLength:], hash[:])
-			if err := batch.Put(keyBuf[:], preimage); err != nil {
-				log.Error("Failed to commit preimage from trie database", "err", err)
+		rawdb.WritePreimages(batch, db.preimages)
+		if batch.ValueSize() > ethdb.IdealBatchSize {
+			if err := batch.Write(); err != nil {
 				return err
 			}
-			if batch.ValueSize() > ethdb.IdealBatchSize {
-				if err := batch.Write(); err != nil {
-					return err
-				}
-				batch.Reset()
-			}
+			batch.Reset()
 		}
 	}
 	// Keep committing nodes from the flush-list until we're below allowance
 	oldest := db.oldest
 	for size > limit && oldest != (common.Hash{}) {
 		// Fetch the oldest referenced node and push into the batch
 		node := db.dirties[oldest]
-		if err := batch.Put(oldest[:], node.rlp()); err != nil {
-			return err
-		}
+		rawdb.WriteTrieNode(batch, oldest, node.rlp())
+
 		// If we exceeded the ideal batch size, commit and reset
 		if batch.ValueSize() >= ethdb.IdealBatchSize {
 			if err := batch.Write(); err != nil {
@@ -662,8 +625,7 @@ func (db *Database) Cap(limit common.StorageSize) error {
 	defer db.lock.Unlock()
 
 	if flushPreimages {
-		db.preimages = make(map[common.Hash][]byte)
-		db.preimagesSize = 0
+		db.preimages, db.preimagesSize = make(map[common.Hash][]byte), 0
 	}
 	for db.oldest != oldest {
 		node := db.dirties[db.oldest]
@@ -706,25 +668,13 @@ func (db *Database) Commit(node common.Hash, report bool, callback func(common.H
 	start := time.Now()
 	batch := db.diskdb.NewBatch()
 
-	// We reuse an ephemeral buffer for the keys. The batch Put operation
-	// copies it internally, so we can reuse it.
-	var keyBuf [secureKeyLength]byte
-	copy(keyBuf[:], secureKeyPrefix)
-
 	// Move all of the accumulated preimages into a write batch
-	for hash, preimage := range db.preimages {
-		copy(keyBuf[secureKeyPrefixLength:], hash[:])
-		if err := batch.Put(keyBuf[:], preimage); err != nil {
-			log.Error("Failed to commit preimage from trie database", "err", err)
+	rawdb.WritePreimages(batch, db.preimages)
+	if batch.ValueSize() > ethdb.IdealBatchSize {
+		if err := batch.Write(); err != nil {
 			return err
 		}
-		// If the batch is too large, flush to disk
-		if batch.ValueSize() > ethdb.IdealBatchSize {
-			if err := batch.Write(); err != nil {
-				return err
-			}
-			batch.Reset()
-		}
+		batch.Reset()
 	}
 	// Since we're going to replay trie node writes into the clean cache, flush out
 	// any batched pre-images before continuing.
@@ -754,8 +704,7 @@ func (db *Database) Commit(node common.Hash, report bool, callback func(common.H
 	batch.Reset()
 
 	// Reset the storage counters and bumpd metrics
-	db.preimages = make(map[common.Hash][]byte)
-	db.preimagesSize = 0
+	db.preimages, db.preimagesSize = make(map[common.Hash][]byte), 0
 
 	memcacheCommitTimeTimer.Update(time.Since(start))
 	memcacheCommitSizeMeter.Mark(int64(storage - db.dirtiesSize))
@@ -791,13 +740,11 @@ func (db *Database) commit(hash common.Hash, batch ethdb.Batch, uncacher *cleane
 	if err != nil {
 		return err
 	}
-	if err := batch.Put(hash[:], node.rlp()); err != nil {
-		return err
-	}
+	// If we've reached an optimal batch size, commit and start over
+	rawdb.WriteTrieNode(batch, hash, node.rlp())
 	if callback != nil {
 		callback(hash)
 	}
-	// If we've reached an optimal batch size, commit and start over
 	if batch.ValueSize() >= ethdb.IdealBatchSize {
 		if err := batch.Write(); err != nil {
 			return err

@@ -130,8 +130,7 @@ func (t *SecureTrie) GetKey(shaKey []byte) []byte {
 	if key, ok := t.getSecKeyCache()[string(shaKey)]; ok {
 		return key
 	}
-	key, _ := t.trie.db.preimage(common.BytesToHash(shaKey))
-	return key
+	return t.trie.db.preimage(common.BytesToHash(shaKey))
 }
 
 // Commit writes all nodes and the secure hash pre-images to the trie's database.

@@ -25,6 +25,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/metrics"
@@ -41,8 +42,8 @@ var (
 )
 
 // syncBloomHasher is a wrapper around a byte blob to satisfy the interface API
-// requirements of the bloom library used. It's used to convert a trie hash into
-// a 64 bit mini hash.
+// requirements of the bloom library used. It's used to convert a trie hash or
+// contract code hash into a 64 bit mini hash.
 type syncBloomHasher []byte
 
 func (f syncBloomHasher) Write(p []byte) (n int, err error) { panic("not implemented") }
@@ -53,9 +54,9 @@ func (f syncBloomHasher) Size() int                         { return 8 }
 func (f syncBloomHasher) Sum64() uint64                     { return binary.BigEndian.Uint64(f) }
 
 // SyncBloom is a bloom filter used during fast sync to quickly decide if a trie
-// node already exists on disk or not. It self populates from the provided disk
-// database on creation in a background thread and will only start returning live
-// results once that's finished.
+// node or contract code already exists on disk or not. It self populates from the
+// provided disk database on creation in a background thread and will only start
+// returning live results once that's finished.
 type SyncBloom struct {
 	bloom  *bloomfilter.Filter
 	inited uint32
@@ -107,10 +108,16 @@ func (b *SyncBloom) init(database ethdb.Iteratee) {
 	)
 	for it.Next() && atomic.LoadUint32(&b.closed) == 0 {
 		// If the database entry is a trie node, add it to the bloom
-		if key := it.Key(); len(key) == common.HashLength {
+		key := it.Key()
+		if len(key) == common.HashLength {
 			b.bloom.Add(syncBloomHasher(key))
 			bloomLoadMeter.Mark(1)
 		}
+		// If the database entry is a contract code, add it to the bloom
+		if ok, hash := rawdb.IsCodeKey(key); ok {
+			b.bloom.Add(syncBloomHasher(hash))
+			bloomLoadMeter.Mark(1)
+		}
 		// If enough time elapsed since the last iterator swap, restart
 		if time.Since(swap) > 8*time.Second {
 			key := common.CopyBytes(it.Key())

@@ -22,6 +22,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/prque"
+	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/ethdb"
 )
 
@@ -37,7 +38,7 @@ var ErrAlreadyProcessed = errors.New("already processed")
 type request struct {
 	hash common.Hash // Hash of the node data content to retrieve
 	data []byte      // Data content of the node, cached until all subtrees complete
-	raw  bool        // Whether this is a raw entry (code) or a trie node
+	code bool        // Whether this is a code entry
 
 	parents []*request // Parent state nodes referencing this entry (notify all upon completion)
 	depth   int        // Depth level within the trie the node is located to prioritise DFS
@@ -46,8 +47,7 @@ type request struct {
 	callback LeafCallback // Callback to invoke if a leaf node it reached on this branch
 }
 
-// SyncResult is a simple list to return missing nodes along with their request
-// hashes.
+// SyncResult is a response with requested data along with it's hash.
 type SyncResult struct {
 	Hash common.Hash // Hash of the originally unknown trie node
 	Data []byte      // Data content of the retrieved node
@@ -56,33 +56,49 @@ type SyncResult struct {
 // syncMemBatch is an in-memory buffer of successfully downloaded but not yet
 // persisted data items.
 type syncMemBatch struct {
-	batch map[common.Hash][]byte // In-memory membatch of recently completed items
+	nodes map[common.Hash][]byte // In-memory membatch of recently completed nodes
+	codes map[common.Hash][]byte // In-memory membatch of recently completed codes
 }
 
 // newSyncMemBatch allocates a new memory-buffer for not-yet persisted trie nodes.
 func newSyncMemBatch() *syncMemBatch {
 	return &syncMemBatch{
-		batch: make(map[common.Hash][]byte),
+		nodes: make(map[common.Hash][]byte),
+		codes: make(map[common.Hash][]byte),
 	}
 }
 
+// hasNode reports the trie node with specific hash is already cached.
+func (batch *syncMemBatch) hasNode(hash common.Hash) bool {
+	_, ok := batch.nodes[hash]
+	return ok
+}
+
+// hasCode reports the contract code with specific hash is already cached.
+func (batch *syncMemBatch) hasCode(hash common.Hash) bool {
+	_, ok := batch.codes[hash]
+	return ok
+}
+
 // Sync is the main state trie synchronisation scheduler, which provides yet
 // unknown trie hashes to retrieve, accepts node data associated with said hashes
 // and reconstructs the trie step by step until all is done.
 type Sync struct {
 	database ethdb.KeyValueReader     // Persistent database to check for existing entries
 	membatch *syncMemBatch            // Memory buffer to avoid frequent database writes
-	requests map[common.Hash]*request // Pending requests pertaining to a key hash
+	nodeReqs map[common.Hash]*request // Pending requests pertaining to a trie node hash
+	codeReqs map[common.Hash]*request // Pending requests pertaining to a code hash
 	queue    *prque.Prque             // Priority queue with the pending requests
-	bloom    *SyncBloom               // Bloom filter for fast node existence checks
+	bloom    *SyncBloom               // Bloom filter for fast state existence checks
 }
 
 // NewSync creates a new trie data download scheduler.
 func NewSync(root common.Hash, database ethdb.KeyValueReader, callback LeafCallback, bloom *SyncBloom) *Sync {
 	ts := &Sync{
 		database: database,
 		membatch: newSyncMemBatch(),
-		requests: make(map[common.Hash]*request),
+		nodeReqs: make(map[common.Hash]*request),
+		codeReqs: make(map[common.Hash]*request),
 		queue:    prque.New(nil),
 		bloom:    bloom,
 	}
@@ -96,13 +112,15 @@ func (s *Sync) AddSubTrie(root common.Hash, depth int, parent common.Hash, callb
 	if root == emptyRoot {
 		return
 	}
-	if _, ok := s.membatch.batch[root]; ok {
+	if s.membatch.hasNode(root) {
 		return
 	}
 	if s.bloom == nil || s.bloom.Contains(root[:]) {
-		// Bloom filter says this might be a duplicate, double check
-		blob, _ := s.database.Get(root[:])
-		if local, err := decodeNode(root[:], blob); local != nil && err == nil {
+		// Bloom filter says this might be a duplicate, double check.
+		// If database says yes, then at least the trie node is present
+		// and we hold the assumption that it's NOT legacy contract code.
+		blob := rawdb.ReadTrieNode(s.database, root)
+		if len(blob) > 0 {
 			return
 		}
 		// False positive, bump fault meter
@@ -116,7 +134,7 @@ func (s *Sync) AddSubTrie(root common.Hash, depth int, parent common.Hash, callb
 	}
 	// If this sub-trie has a designated parent, link them together
 	if parent != (common.Hash{}) {
-		ancestor := s.requests[parent]
+		ancestor := s.nodeReqs[parent]
 		if ancestor == nil {
 			panic(fmt.Sprintf("sub-trie ancestor not found: %x", parent))
 		}
@@ -126,21 +144,25 @@ func (s *Sync) AddSubTrie(root common.Hash, depth int, parent common.Hash, callb
 	s.schedule(req)
 }
 
-// AddRawEntry schedules the direct retrieval of a state entry that should not be
-// interpreted as a trie node, but rather accepted and stored into the database
-// as is. This method's goal is to support misc state metadata retrievals (e.g.
-// contract code).
-func (s *Sync) AddRawEntry(hash common.Hash, depth int, parent common.Hash) {
+// AddCodeEntry schedules the direct retrieval of a contract code that should not
+// be interpreted as a trie node, but rather accepted and stored into the database
+// as is.
+func (s *Sync) AddCodeEntry(hash common.Hash, depth int, parent common.Hash) {
 	// Short circuit if the entry is empty or already known
 	if hash == emptyState {
 		return
 	}
-	if _, ok := s.membatch.batch[hash]; ok {
+	if s.membatch.hasCode(hash) {
 		return
 	}
 	if s.bloom == nil || s.bloom.Contains(hash[:]) {
-		// Bloom filter says this might be a duplicate, double check
-		if ok, _ := s.database.Has(hash[:]); ok {
+		// Bloom filter says this might be a duplicate, double check.
+		// If database says yes, the blob is present for sure.
+		// Note we only check the existence with new code scheme, fast
+		// sync is expected to run with a fresh new node. Even there
+		// exists the code with legacy format, fetch and store with
+		// new scheme anyway.
+		if blob := rawdb.ReadCodeWithPrefix(s.database, hash); len(blob) > 0 {
 			return
 		}
 		// False positive, bump fault meter
@@ -149,12 +171,12 @@ func (s *Sync) AddRawEntry(hash common.Hash, depth int, parent common.Hash) {
 	// Assemble the new sub-trie sync request
 	req := &request{
 		hash:  hash,
-		raw:   true,
+		code:  true,
 		depth: depth,
 	}
 	// If this sub-trie has a designated parent, link them together
 	if parent != (common.Hash{}) {
-		ancestor := s.requests[parent]
+		ancestor := s.nodeReqs[parent] // the parent of codereq can ONLY be nodereq
 		if ancestor == nil {
 			panic(fmt.Sprintf("raw-entry ancestor not found: %x", parent))
 		}
@@ -173,61 +195,64 @@ func (s *Sync) Missing(max int) []common.Hash {
 	return requests
 }
 
-// Process injects a batch of retrieved trie nodes data, returning if something
-// was committed to the database and also the index of an entry if its processing
-// failed.
-func (s *Sync) Process(results []SyncResult) (bool, int, error) {
-	committed := false
-
-	for i, item := range results {
-		// If the item was not requested, bail out
-		request := s.requests[item.Hash]
-		if request == nil {
-			return committed, i, ErrNotRequested
-		}
-		if request.data != nil {
-			return committed, i, ErrAlreadyProcessed
-		}
-		// If the item is a raw entry request, commit directly
-		if request.raw {
-			request.data = item.Data
-			s.commit(request)
-			committed = true
-			continue
-		}
+// Process injects the received data for requested item. Note it can
+// happpen that the single response commits two pending requests(e.g.
+// there are two requests one for code and one for node but the hash
+// is same). In this case the second response for the same hash will
+// be treated as "non-requested" item or "already-processed" item but
+// there is no downside.
+func (s *Sync) Process(result SyncResult) error {
+	// If the item was not requested either for code or node, bail out
+	if s.nodeReqs[result.Hash] == nil && s.codeReqs[result.Hash] == nil {
+		return ErrNotRequested
+	}
+	// There is an pending code request for this data, commit directly
+	var filled bool
+	if req := s.codeReqs[result.Hash]; req != nil && req.data == nil {
+		filled = true
+		req.data = result.Data
+		s.commit(req)
+	}
+	// There is an pending node request for this data, fill it.
+	if req := s.nodeReqs[result.Hash]; req != nil && req.data == nil {
+		filled = true
 		// Decode the node data content and update the request
-		node, err := decodeNode(item.Hash[:], item.Data)
+		node, err := decodeNode(result.Hash[:], result.Data)
 		if err != nil {
-			return committed, i, err
+			return err
 		}
-		request.data = item.Data
+		req.data = result.Data
 
 		// Create and schedule a request for all the children nodes
-		requests, err := s.children(request, node)
+		requests, err := s.children(req, node)
 		if err != nil {
-			return committed, i, err
-		}
-		if len(requests) == 0 && request.deps == 0 {
-			s.commit(request)
-			committed = true
-			continue
+			return err
 		}
-		request.deps += len(requests)
-		for _, child := range requests {
-			s.schedule(child)
+		if len(requests) == 0 && req.deps == 0 {
+			s.commit(req)
+		} else {
+			req.deps += len(requests)
+			for _, child := range requests {
+				s.schedule(child)
+			}
 		}
 	}
-	return committed, 0, nil
+	if !filled {
+		return ErrAlreadyProcessed
+	}
+	return nil
 }
 
 // Commit flushes the data stored in the internal membatch out to persistent
 // storage, returning any occurred error.
 func (s *Sync) Commit(dbw ethdb.Batch) error {
 	// Dump the membatch into a database dbw
-	for key, value := range s.membatch.batch {
-		if err := dbw.Put(key[:], value); err != nil {
-			return err
-		}
+	for key, value := range s.membatch.nodes {
+		rawdb.WriteTrieNode(dbw, key, value)
+		s.bloom.Add(key[:])
+	}
+	for key, value := range s.membatch.codes {
+		rawdb.WriteCode(dbw, key, value)
 		s.bloom.Add(key[:])
 	}
 	// Drop the membatch data and return
@@ -237,21 +262,30 @@ func (s *Sync) Commit(dbw ethdb.Batch) error {
 
 // Pending returns the number of state entries currently pending for download.
 func (s *Sync) Pending() int {
-	return len(s.requests)
+	return len(s.nodeReqs) + len(s.codeReqs)
 }
 
 // schedule inserts a new state retrieval request into the fetch queue. If there
 // is already a pending request for this node, the new request will be discarded
 // and only a parent reference added to the old one.
 func (s *Sync) schedule(req *request) {
+	var reqset = s.nodeReqs
+	if req.code {
+		reqset = s.codeReqs
+	}
 	// If we're already requesting this node, add a new reference and stop
-	if old, ok := s.requests[req.hash]; ok {
+	if old, ok := reqset[req.hash]; ok {
 		old.parents = append(old.parents, req.parents...)
 		return
 	}
-	// Schedule the request for future retrieval
+	reqset[req.hash] = req
+
+	// Schedule the request for future retrieval. This queue is shared
+	// by both node requests and code requests. It can happen that there
+	// is a trie node and code has same hash. In this case two elements
+	// with same hash and same or different depth will be pushed. But it's
+	// ok the worst case is the second response will be treated as duplicated.
 	s.queue.Push(req.hash, int64(req.depth))
-	s.requests[req.hash] = req
 }
 
 // children retrieves all the missing children of a state trie entry for future
@@ -297,12 +331,14 @@ func (s *Sync) children(req *request, object node) ([]*request, error) {
 		if node, ok := (child.node).(hashNode); ok {
 			// Try to resolve the node from the local database
 			hash := common.BytesToHash(node)
-			if _, ok := s.membatch.batch[hash]; ok {
+			if s.membatch.hasNode(hash) {
 				continue
 			}
 			if s.bloom == nil || s.bloom.Contains(node) {
-				// Bloom filter says this might be a duplicate, double check
-				if ok, _ := s.database.Has(node); ok {
+				// Bloom filter says this might be a duplicate, double check.
+				// If database says yes, then at least the trie node is present
+				// and we hold the assumption that it's NOT legacy contract code.
+				if blob := rawdb.ReadTrieNode(s.database, common.BytesToHash(node)); len(blob) > 0 {
 					continue
 				}
 				// False positive, bump fault meter
@@ -325,10 +361,13 @@ func (s *Sync) children(req *request, object node) ([]*request, error) {
 // committed themselves.
 func (s *Sync) commit(req *request) (err error) {
 	// Write the node content to the membatch
-	s.membatch.batch[req.hash] = req.data
-
-	delete(s.requests, req.hash)
-
+	if req.code {
+		s.membatch.codes[req.hash] = req.data
+		delete(s.codeReqs, req.hash)
+	} else {
+		s.membatch.nodes[req.hash] = req.data
+		delete(s.nodeReqs, req.hash)
+	}
 	// Check all parents for completion
 	for _, parent := range req.parents {
 		parent.deps--

@@ -124,8 +124,10 @@ func testIterativeSync(t *testing.T, count int) {
 			}
 			results[i] = SyncResult{hash, data}
 		}
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := diskdb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -160,8 +162,10 @@ func TestIterativeDelayedSync(t *testing.T) {
 			}
 			results[i] = SyncResult{hash, data}
 		}
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := diskdb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -204,8 +208,10 @@ func testIterativeRandomSync(t *testing.T, count int) {
 			results = append(results, SyncResult{hash, data})
 		}
 		// Feed the retrieved results back and queue new tasks
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := diskdb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -251,8 +257,10 @@ func TestIterativeRandomDelayedSync(t *testing.T) {
 			}
 		}
 		// Feed the retrieved results back and queue new tasks
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := diskdb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -298,8 +306,10 @@ func TestDuplicateAvoidanceSync(t *testing.T) {
 
 			results[i] = SyncResult{hash, data}
 		}
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := diskdb.NewBatch()
 		if err := sched.Commit(batch); err != nil {
@@ -336,8 +346,10 @@ func TestIncompleteSync(t *testing.T) {
 			results[i] = SyncResult{hash, data}
 		}
 		// Process each of the trie nodes
-		if _, index, err := sched.Process(results); err != nil {
-			t.Fatalf("failed to process result #%d: %v", index, err)
+		for _, result := range results {
+			if err := sched.Process(result); err != nil {
+				t.Fatalf("failed to process result %v", err)
+			}
 		}
 		batch := diskdb.NewBatch()
 		if err := sched.Commit(batch); err != nil {

@@ -473,3 +473,9 @@ func (t *Trie) hashRoot(db *Database) (node, node, error) {
 	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
+}