all: integrate the freezer with fast sync

* all: freezer style syncing

core, eth, les, light: clean up freezer relative APIs

core, eth, les, trie, ethdb, light: clean a bit

core, eth, les, light: add unit tests

core, light: rewrite setHead function

core, eth: fix downloader unit tests

core: add receipt chain insertion test

core: use constant instead of hardcoding table name

core: fix rollback

core: fix setHead

core/rawdb: remove canonical block first and then iterate side chain

core/rawdb, ethdb: add hasAncient interface

eth/downloader: calculate ancient limit via cht first

core, eth, ethdb: lots of fixes

* eth/downloader: print ancient disable log only for fast sync

13 files changed, 895 insertions, 267 deletions

diff --git a/core/blockchain.go b/core/blockchain.go
index 61b809319..4ac2c3a44 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -63,6 +63,8 @@ var (
 
 	blockPrefetchExecuteTimer   = metrics.NewRegisteredTimer("chain/prefetch/executes", nil)
 	blockPrefetchInterruptMeter = metrics.NewRegisteredMeter("chain/prefetch/interrupts", nil)
+
+	errInsertionInterrupted = errors.New("insertion is interrupted")
 )
 
 const (
@@ -138,7 +140,6 @@ type BlockChain struct {
 
 	chainmu sync.RWMutex // blockchain insertion lock
 
-	checkpoint       int          // checkpoint counts towards the new checkpoint
 	currentBlock     atomic.Value // Current head of the block chain
 	currentFastBlock atomic.Value // Current head of the fast-sync chain (may be above the block chain!)
 
@@ -161,8 +162,9 @@ type BlockChain struct {
 	processor  Processor  // Block transaction processor interface
 	vmConfig   vm.Config
 
-	badBlocks      *lru.Cache              // Bad block cache
-	shouldPreserve func(*types.Block) bool // Function used to determine whether should preserve the given block.
+	badBlocks       *lru.Cache                     // Bad block cache
+	shouldPreserve  func(*types.Block) bool        // Function used to determine whether should preserve the given block.
+	terminateInsert func(common.Hash, uint64) bool // Testing hook used to terminate ancient receipt chain insertion.
 }
 
 // NewBlockChain returns a fully initialised block chain using information
@@ -216,6 +218,39 @@ func NewBlockChain(db ethdb.Database, cacheConfig *CacheConfig, chainConfig *par
 	if err := bc.loadLastState(); err != nil {
 		return nil, err
 	}
+	if frozen, err := bc.db.Ancients(); err == nil && frozen >= 1 {
+		var (
+			needRewind bool
+			low        uint64
+		)
+		// The head full block may be rolled back to a very low height due to
+		// blockchain repair. If the head full block is even lower than the ancient
+		// chain, truncate the ancient store.
+		fullBlock := bc.CurrentBlock()
+		if fullBlock != nil && fullBlock != bc.genesisBlock && fullBlock.NumberU64() < frozen-1 {
+			needRewind = true
+			low = fullBlock.NumberU64()
+		}
+		// In fast sync, it may happen that ancient data has been written to the
+		// ancient store, but the LastFastBlock has not been updated, truncate the
+		// extra data here.
+		fastBlock := bc.CurrentFastBlock()
+		if fastBlock != nil && fastBlock.NumberU64() < frozen-1 {
+			needRewind = true
+			if fastBlock.NumberU64() < low || low == 0 {
+				low = fastBlock.NumberU64()
+			}
+		}
+		if needRewind {
+			var hashes []common.Hash
+			previous := bc.CurrentHeader().Number.Uint64()
+			for i := low + 1; i <= bc.CurrentHeader().Number.Uint64(); i++ {
+				hashes = append(hashes, rawdb.ReadCanonicalHash(bc.db, i))
+			}
+			bc.Rollback(hashes)
+			log.Warn("Truncate ancient chain", "from", previous, "to", low)
+		}
+	}
 	// Check the current state of the block hashes and make sure that we do not have any of the bad blocks in our chain
 	for hash := range BadHashes {
 		if header := bc.GetHeaderByHash(hash); header != nil {
@@ -267,6 +302,7 @@ func (bc *BlockChain) loadLastState() error {
 		if err := bc.repair(&currentBlock); err != nil {
 			return err
 		}
+		rawdb.WriteHeadBlockHash(bc.db, currentBlock.Hash())
 	}
 	// Everything seems to be fine, set as the head block
 	bc.currentBlock.Store(currentBlock)
@@ -312,12 +348,55 @@ func (bc *BlockChain) SetHead(head uint64) error {
 	bc.chainmu.Lock()
 	defer bc.chainmu.Unlock()
 
-	// Rewind the header chain, deleting all block bodies until then
-	delFn := func(db ethdb.Writer, hash common.Hash, num uint64) {
-		rawdb.DeleteBody(db, hash, num)
+	updateFn := func(db ethdb.KeyValueWriter, header *types.Header) {
+		// Rewind the block chain, ensuring we don't end up with a stateless head block
+		if currentBlock := bc.CurrentBlock(); currentBlock != nil && header.Number.Uint64() < currentBlock.NumberU64() {
+			newHeadBlock := bc.GetBlock(header.Hash(), header.Number.Uint64())
+			if newHeadBlock == nil {
+				newHeadBlock = bc.genesisBlock
+			} else {
+				if _, err := state.New(newHeadBlock.Root(), bc.stateCache); err != nil {
+					// Rewound state missing, rolled back to before pivot, reset to genesis
+					newHeadBlock = bc.genesisBlock
+				}
+			}
+			rawdb.WriteHeadBlockHash(db, newHeadBlock.Hash())
+			bc.currentBlock.Store(newHeadBlock)
+		}
+
+		// Rewind the fast block in a simpleton way to the target head
+		if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock != nil && header.Number.Uint64() < currentFastBlock.NumberU64() {
+			newHeadFastBlock := bc.GetBlock(header.Hash(), header.Number.Uint64())
+			// If either blocks reached nil, reset to the genesis state
+			if newHeadFastBlock == nil {
+				newHeadFastBlock = bc.genesisBlock
+			}
+			rawdb.WriteHeadFastBlockHash(db, newHeadFastBlock.Hash())
+			bc.currentFastBlock.Store(newHeadFastBlock)
+		}
 	}
-	bc.hc.SetHead(head, delFn)
-	currentHeader := bc.hc.CurrentHeader()
+
+	// Rewind the header chain, deleting all block bodies until then
+	delFn := func(db ethdb.KeyValueWriter, hash common.Hash, num uint64) {
+		// Ignore the error here since light client won't hit this path
+		frozen, _ := bc.db.Ancients()
+		if num+1 <= frozen {
+			// Truncate all relative data(header, total difficulty, body, receipt
+			// and canonical hash) from ancient store.
+			bc.db.TruncateAncients(num + 1)
+
+			// Remove the hash <-> number mapping from the active store.
+			rawdb.DeleteHeaderNumber(db, hash)
+		} else {
+			// Remove relative body and receipts from the active store.
+			// The header, total difficulty and canonical hash will be
+			// removed in the hc.SetHead function.
+			rawdb.DeleteBody(db, hash, num)
+			rawdb.DeleteReceipts(db, hash, num)
+		}
+		// Todo(rjl493456442) txlookup, bloombits, etc
+	}
+	bc.hc.SetHead(head, updateFn, delFn)
 
 	// Clear out any stale content from the caches
 	bc.bodyCache.Purge()
@@ -326,33 +405,6 @@ func (bc *BlockChain) SetHead(head uint64) error {
 	bc.blockCache.Purge()
 	bc.futureBlocks.Purge()
 
-	// Rewind the block chain, ensuring we don't end up with a stateless head block
-	if currentBlock := bc.CurrentBlock(); currentBlock != nil && currentHeader.Number.Uint64() < currentBlock.NumberU64() {
-		bc.currentBlock.Store(bc.GetBlock(currentHeader.Hash(), currentHeader.Number.Uint64()))
-	}
-	if currentBlock := bc.CurrentBlock(); currentBlock != nil {
-		if _, err := state.New(currentBlock.Root(), bc.stateCache); err != nil {
-			// Rewound state missing, rolled back to before pivot, reset to genesis
-			bc.currentBlock.Store(bc.genesisBlock)
-		}
-	}
-	// Rewind the fast block in a simpleton way to the target head
-	if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock != nil && currentHeader.Number.Uint64() < currentFastBlock.NumberU64() {
-		bc.currentFastBlock.Store(bc.GetBlock(currentHeader.Hash(), currentHeader.Number.Uint64()))
-	}
-	// If either blocks reached nil, reset to the genesis state
-	if currentBlock := bc.CurrentBlock(); currentBlock == nil {
-		bc.currentBlock.Store(bc.genesisBlock)
-	}
-	if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock == nil {
-		bc.currentFastBlock.Store(bc.genesisBlock)
-	}
-	currentBlock := bc.CurrentBlock()
-	currentFastBlock := bc.CurrentFastBlock()
-
-	rawdb.WriteHeadBlockHash(bc.db, currentBlock.Hash())
-	rawdb.WriteHeadFastBlockHash(bc.db, currentFastBlock.Hash())
-
 	return bc.loadLastState()
 }
 
@@ -780,96 +832,259 @@ func (bc *BlockChain) Rollback(chain []common.Hash) {
 		}
 		if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock.Hash() == hash {
 			newFastBlock := bc.GetBlock(currentFastBlock.ParentHash(), currentFastBlock.NumberU64()-1)
-			bc.currentFastBlock.Store(newFastBlock)
 			rawdb.WriteHeadFastBlockHash(bc.db, newFastBlock.Hash())
+			bc.currentFastBlock.Store(newFastBlock)
 		}
 		if currentBlock := bc.CurrentBlock(); currentBlock.Hash() == hash {
 			newBlock := bc.GetBlock(currentBlock.ParentHash(), currentBlock.NumberU64()-1)
-			bc.currentBlock.Store(newBlock)
 			rawdb.WriteHeadBlockHash(bc.db, newBlock.Hash())
+			bc.currentBlock.Store(newBlock)
 		}
 	}
+	// Truncate ancient data which exceeds the current header.
+	//
+	// Notably, it can happen that system crashes without truncating the ancient data
+	// but the head indicator has been updated in the active store. Regarding this issue,
+	// system will self recovery by truncating the extra data during the setup phase.
+	if err := bc.truncateAncient(bc.hc.CurrentHeader().Number.Uint64()); err != nil {
+		log.Crit("Truncate ancient store failed", "err", err)
+	}
+}
+
+// truncateAncient rewinds the blockchain to the specified header and deletes all
+// data in the ancient store that exceeds the specified header.
+func (bc *BlockChain) truncateAncient(head uint64) error {
+	frozen, err := bc.db.Ancients()
+	if err != nil {
+		return err
+	}
+	// Short circuit if there is no data to truncate in ancient store.
+	if frozen <= head+1 {
+		return nil
+	}
+	// Truncate all the data in the freezer beyond the specified head
+	if err := bc.db.TruncateAncients(head + 1); err != nil {
+		return err
+	}
+	// Clear out any stale content from the caches
+	bc.hc.headerCache.Purge()
+	bc.hc.tdCache.Purge()
+	bc.hc.numberCache.Purge()
+
+	// Clear out any stale content from the caches
+	bc.bodyCache.Purge()
+	bc.bodyRLPCache.Purge()
+	bc.receiptsCache.Purge()
+	bc.blockCache.Purge()
+	bc.futureBlocks.Purge()
+
+	log.Info("Rewind ancient data", "number", head)
+	return nil
 }
 
 // InsertReceiptChain attempts to complete an already existing header chain with
 // transaction and receipt data.
-func (bc *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
+func (bc *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain []types.Receipts, ancientLimit uint64) (int, error) {
 	bc.wg.Add(1)
 	defer bc.wg.Done()
 
+	var (
+		ancientBlocks, liveBlocks     types.Blocks
+		ancientReceipts, liveReceipts []types.Receipts
+	)
 	// Do a sanity check that the provided chain is actually ordered and linked
-	for i := 1; i < len(blockChain); i++ {
-		if blockChain[i].NumberU64() != blockChain[i-1].NumberU64()+1 || blockChain[i].ParentHash() != blockChain[i-1].Hash() {
-			log.Error("Non contiguous receipt insert", "number", blockChain[i].Number(), "hash", blockChain[i].Hash(), "parent", blockChain[i].ParentHash(),
-				"prevnumber", blockChain[i-1].Number(), "prevhash", blockChain[i-1].Hash())
-			return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, blockChain[i-1].NumberU64(),
-				blockChain[i-1].Hash().Bytes()[:4], i, blockChain[i].NumberU64(), blockChain[i].Hash().Bytes()[:4], blockChain[i].ParentHash().Bytes()[:4])
+	for i := 0; i < len(blockChain); i++ {
+		if i != 0 {
+			if blockChain[i].NumberU64() != blockChain[i-1].NumberU64()+1 || blockChain[i].ParentHash() != blockChain[i-1].Hash() {
+				log.Error("Non contiguous receipt insert", "number", blockChain[i].Number(), "hash", blockChain[i].Hash(), "parent", blockChain[i].ParentHash(),
+					"prevnumber", blockChain[i-1].Number(), "prevhash", blockChain[i-1].Hash())
+				return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, blockChain[i-1].NumberU64(),
+					blockChain[i-1].Hash().Bytes()[:4], i, blockChain[i].NumberU64(), blockChain[i].Hash().Bytes()[:4], blockChain[i].ParentHash().Bytes()[:4])
+			}
+		}
+		if blockChain[i].NumberU64() <= ancientLimit {
+			ancientBlocks, ancientReceipts = append(ancientBlocks, blockChain[i]), append(ancientReceipts, receiptChain[i])
+		} else {
+			liveBlocks, liveReceipts = append(liveBlocks, blockChain[i]), append(liveReceipts, receiptChain[i])
 		}
 	}
 
 	var (
 		stats = struct{ processed, ignored int32 }{}
 		start = time.Now()
-		bytes = 0
-		batch = bc.db.NewBatch()
+		size  = 0
 	)
-	for i, block := range blockChain {
-		receipts := receiptChain[i]
-		// Short circuit insertion if shutting down or processing failed
-		if atomic.LoadInt32(&bc.procInterrupt) == 1 {
-			return 0, nil
+	// updateHead updates the head fast sync block if the inserted blocks are better
+	// and returns a indicator whether the inserted blocks are canonical.
+	updateHead := func(head *types.Block) bool {
+		var isCanonical bool
+		bc.chainmu.Lock()
+		if td := bc.GetTd(head.Hash(), head.NumberU64()); td != nil { // Rewind may have occurred, skip in that case
+			currentFastBlock := bc.CurrentFastBlock()
+			if bc.GetTd(currentFastBlock.Hash(), currentFastBlock.NumberU64()).Cmp(td) < 0 {
+				rawdb.WriteHeadFastBlockHash(bc.db, head.Hash())
+				bc.currentFastBlock.Store(head)
+				isCanonical = true
+			}
+		}
+		bc.chainmu.Unlock()
+		return isCanonical
+	}
+	// writeAncient writes blockchain and corresponding receipt chain into ancient store.
+	//
+	// this function only accepts canonical chain data. All side chain will be reverted
+	// eventually.
+	writeAncient := func(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
+		var (
+			previous = bc.CurrentFastBlock()
+			batch    = bc.db.NewBatch()
+		)
+		// If any error occurs before updating the head or we are inserting a side chain,
+		// all the data written this time wll be rolled back.
+		defer func() {
+			if previous != nil {
+				if err := bc.truncateAncient(previous.NumberU64()); err != nil {
+					log.Crit("Truncate ancient store failed", "err", err)
+				}
+			}
+		}()
+		for i, block := range blockChain {
+			// Short circuit insertion if shutting down or processing failed
+			if atomic.LoadInt32(&bc.procInterrupt) == 1 {
+				return 0, errInsertionInterrupted
+			}
+			// Short circuit insertion if it is required(used in testing only)
+			if bc.terminateInsert != nil && bc.terminateInsert(block.Hash(), block.NumberU64()) {
+				return i, errors.New("insertion is terminated for testing purpose")
+			}
+			// Short circuit if the owner header is unknown
+			if !bc.HasHeader(block.Hash(), block.NumberU64()) {
+				return i, fmt.Errorf("containing header #%d [%x…] unknown", block.Number(), block.Hash().Bytes()[:4])
+			}
+			// Compute all the non-consensus fields of the receipts
+			if err := receiptChain[i].DeriveFields(bc.chainConfig, block.Hash(), block.NumberU64(), block.Transactions()); err != nil {
+				return i, fmt.Errorf("failed to derive receipts data: %v", err)
+			}
+			// Initialize freezer with genesis block first
+			if frozen, err := bc.db.Ancients(); err == nil && frozen == 0 && block.NumberU64() == 1 {
+				genesisBlock := rawdb.ReadBlock(bc.db, rawdb.ReadCanonicalHash(bc.db, 0), 0)
+				size += rawdb.WriteAncientBlock(bc.db, genesisBlock, nil, genesisBlock.Difficulty())
+			}
+			// Flush data into ancient store.
+			size += rawdb.WriteAncientBlock(bc.db, block, receiptChain[i], bc.GetTd(block.Hash(), block.NumberU64()))
+			rawdb.WriteTxLookupEntries(batch, block)
+
+			stats.processed++
 		}
-		// Short circuit if the owner header is unknown
-		if !bc.HasHeader(block.Hash(), block.NumberU64()) {
-			return i, fmt.Errorf("containing header #%d [%x…] unknown", block.Number(), block.Hash().Bytes()[:4])
+		// Flush all tx-lookup index data.
+		size += batch.ValueSize()
+		if err := batch.Write(); err != nil {
+			return 0, err
 		}
-		// Skip if the entire data is already known
-		if bc.HasBlock(block.Hash(), block.NumberU64()) {
-			stats.ignored++
-			continue
+		batch.Reset()
+
+		// Sync the ancient store explicitly to ensure all data has been flushed to disk.
+		if err := bc.db.Sync(); err != nil {
+			return 0, err
 		}
-		// Compute all the non-consensus fields of the receipts
-		if err := receipts.DeriveFields(bc.chainConfig, block.Hash(), block.NumberU64(), block.Transactions()); err != nil {
-			return i, fmt.Errorf("failed to derive receipts data: %v", err)
+		if !updateHead(blockChain[len(blockChain)-1]) {
+			return 0, errors.New("side blocks can't be accepted as the ancient chain data")
 		}
-		// Write all the data out into the database
-		rawdb.WriteBody(batch, block.Hash(), block.NumberU64(), block.Body())
-		rawdb.WriteReceipts(batch, block.Hash(), block.NumberU64(), receipts)
-		rawdb.WriteTxLookupEntries(batch, block)
+		previous = nil // disable rollback explicitly
 
-		stats.processed++
+		// Remove the ancient data from the active store
+		cleanGenesis := len(blockChain) > 0 && blockChain[0].NumberU64() == 1
+		if cleanGenesis {
+			// Migrate genesis block to ancient store too.
+			rawdb.DeleteBlockWithoutNumber(batch, rawdb.ReadCanonicalHash(bc.db, 0), 0)
+			rawdb.DeleteCanonicalHash(batch, 0)
+		}
+		// Wipe out canonical block data.
+		for _, block := range blockChain {
+			rawdb.DeleteBlockWithoutNumber(batch, block.Hash(), block.NumberU64())
+			rawdb.DeleteCanonicalHash(batch, block.NumberU64())
+		}
+		if err := batch.Write(); err != nil {
+			return 0, err
+		}
+		batch.Reset()
+		// Wipe out side chain too.
+		for _, block := range blockChain {
+			for _, hash := range rawdb.ReadAllHashes(bc.db, block.NumberU64()) {
+				rawdb.DeleteBlock(batch, hash, block.NumberU64())
+			}
+		}
+		if err := batch.Write(); err != nil {
+			return 0, err
+		}
+		return 0, nil
+	}
+	// writeLive writes blockchain and corresponding receipt chain into active store.
+	writeLive := func(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
+		batch := bc.db.NewBatch()
+		for i, block := range blockChain {
+			// Short circuit insertion if shutting down or processing failed
+			if atomic.LoadInt32(&bc.procInterrupt) == 1 {
+				return 0, errInsertionInterrupted
+			}
+			// Short circuit if the owner header is unknown
+			if !bc.HasHeader(block.Hash(), block.NumberU64()) {
+				return i, fmt.Errorf("containing header #%d [%x…] unknown", block.Number(), block.Hash().Bytes()[:4])
+			}
+			if bc.HasBlock(block.Hash(), block.NumberU64()) {
+				stats.ignored++
+				continue
+			}
+			// Compute all the non-consensus fields of the receipts
+			if err := receiptChain[i].DeriveFields(bc.chainConfig, block.Hash(), block.NumberU64(), block.Transactions()); err != nil {
+				return i, fmt.Errorf("failed to derive receipts data: %v", err)
+			}
+			// Write all the data out into the database
+			rawdb.WriteBody(batch, block.Hash(), block.NumberU64(), block.Body())
+			rawdb.WriteReceipts(batch, block.Hash(), block.NumberU64(), receiptChain[i])
+			rawdb.WriteTxLookupEntries(batch, block)
 
-		if batch.ValueSize() >= ethdb.IdealBatchSize {
+			stats.processed++
+			if batch.ValueSize() >= ethdb.IdealBatchSize {
+				if err := batch.Write(); err != nil {
+					return 0, err
+				}
+				size += batch.ValueSize()
+				batch.Reset()
+			}
+		}
+		if batch.ValueSize() > 0 {
+			size += batch.ValueSize()
 			if err := batch.Write(); err != nil {
 				return 0, err
 			}
-			bytes += batch.ValueSize()
-			batch.Reset()
 		}
+		updateHead(blockChain[len(blockChain)-1])
+		return 0, nil
 	}
-	if batch.ValueSize() > 0 {
-		bytes += batch.ValueSize()
-		if err := batch.Write(); err != nil {
-			return 0, err
+	// Write downloaded chain data and corresponding receipt chain data.
+	if len(ancientBlocks) > 0 {
+		if n, err := writeAncient(ancientBlocks, ancientReceipts); err != nil {
+			if err == errInsertionInterrupted {
+				return 0, nil
+			}
+			return n, err
 		}
 	}
-
-	// Update the head fast sync block if better
-	bc.chainmu.Lock()
-	head := blockChain[len(blockChain)-1]
-	if td := bc.GetTd(head.Hash(), head.NumberU64()); td != nil { // Rewind may have occurred, skip in that case
-		currentFastBlock := bc.CurrentFastBlock()
-		if bc.GetTd(currentFastBlock.Hash(), currentFastBlock.NumberU64()).Cmp(td) < 0 {
-			rawdb.WriteHeadFastBlockHash(bc.db, head.Hash())
-			bc.currentFastBlock.Store(head)
+	if len(liveBlocks) > 0 {
+		if n, err := writeLive(liveBlocks, liveReceipts); err != nil {
+			if err == errInsertionInterrupted {
+				return 0, nil
+			}
+			return n, err
 		}
 	}
-	bc.chainmu.Unlock()
 
+	head := blockChain[len(blockChain)-1]
 	context := []interface{}{
 		"count", stats.processed, "elapsed", common.PrettyDuration(time.Since(start)),
 		"number", head.Number(), "hash", head.Hash(), "age", common.PrettyAge(time.Unix(int64(head.Time()), 0)),
-		"size", common.StorageSize(bytes),
+		"size", common.StorageSize(size),
 	}
 	if stats.ignored > 0 {
 		context = append(context, []interface{}{"ignored", stats.ignored}...)
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index 70e3207f5..7b1a9a54f 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -18,8 +18,10 @@ package core
 
 import (
 	"fmt"
+	"io/ioutil"
 	"math/big"
 	"math/rand"
+	"os"
 	"sync"
 	"testing"
 	"time"
@@ -33,7 +35,6 @@ import (
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
-	"github.com/ethereum/go-ethereum/ethdb/memorydb"
 	"github.com/ethereum/go-ethereum/params"
 )
 
@@ -639,7 +640,27 @@ func TestFastVsFullChains(t *testing.T) {
 	if n, err := fast.InsertHeaderChain(headers, 1); err != nil {
 		t.Fatalf("failed to insert header %d: %v", n, err)
 	}
-	if n, err := fast.InsertReceiptChain(blocks, receipts); err != nil {
+	if n, err := fast.InsertReceiptChain(blocks, receipts, 0); err != nil {
+		t.Fatalf("failed to insert receipt %d: %v", n, err)
+	}
+	// Freezer style fast import the chain.
+	frdir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("failed to create temp freezer dir: %v", err)
+	}
+	defer os.Remove(frdir)
+	ancientDb, err := rawdb.NewDatabaseWithFreezer(rawdb.NewMemoryDatabase(), frdir, "")
+	if err != nil {
+		t.Fatalf("failed to create temp freezer db: %v", err)
+	}
+	gspec.MustCommit(ancientDb)
+	ancient, _ := NewBlockChain(ancientDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{}, nil)
+	defer ancient.Stop()
+
+	if n, err := ancient.InsertHeaderChain(headers, 1); err != nil {
+		t.Fatalf("failed to insert header %d: %v", n, err)
+	}
+	if n, err := ancient.InsertReceiptChain(blocks, receipts, uint64(len(blocks)/2)); err != nil {
 		t.Fatalf("failed to insert receipt %d: %v", n, err)
 	}
 	// Iterate over all chain data components, and cross reference
@@ -647,26 +668,35 @@ func TestFastVsFullChains(t *testing.T) {
 		num, hash := blocks[i].NumberU64(), blocks[i].Hash()
 
 		if ftd, atd := fast.GetTdByHash(hash), archive.GetTdByHash(hash); ftd.Cmp(atd) != 0 {
-			t.Errorf("block #%d [%x]: td mismatch: have %v, want %v", num, hash, ftd, atd)
+			t.Errorf("block #%d [%x]: td mismatch: fastdb %v, archivedb %v", num, hash, ftd, atd)
+		}
+		if antd, artd := ancient.GetTdByHash(hash), archive.GetTdByHash(hash); antd.Cmp(artd) != 0 {
+			t.Errorf("block #%d [%x]: td mismatch: ancientdb %v, archivedb %v", num, hash, antd, artd)
 		}
 		if fheader, aheader := fast.GetHeaderByHash(hash), archive.GetHeaderByHash(hash); fheader.Hash() != aheader.Hash() {
-			t.Errorf("block #%d [%x]: header mismatch: have %v, want %v", num, hash, fheader, aheader)
+			t.Errorf("block #%d [%x]: header mismatch: fastdb %v, archivedb %v", num, hash, fheader, aheader)
+		}
+		if anheader, arheader := ancient.GetHeaderByHash(hash), archive.GetHeaderByHash(hash); anheader.Hash() != arheader.Hash() {
+			t.Errorf("block #%d [%x]: header mismatch: ancientdb %v, archivedb %v", num, hash, anheader, arheader)
 		}
-		if fblock, ablock := fast.GetBlockByHash(hash), archive.GetBlockByHash(hash); fblock.Hash() != ablock.Hash() {
-			t.Errorf("block #%d [%x]: block mismatch: have %v, want %v", num, hash, fblock, ablock)
-		} else if types.DeriveSha(fblock.Transactions()) != types.DeriveSha(ablock.Transactions()) {
-			t.Errorf("block #%d [%x]: transactions mismatch: have %v, want %v", num, hash, fblock.Transactions(), ablock.Transactions())
-		} else if types.CalcUncleHash(fblock.Uncles()) != types.CalcUncleHash(ablock.Uncles()) {
-			t.Errorf("block #%d [%x]: uncles mismatch: have %v, want %v", num, hash, fblock.Uncles(), ablock.Uncles())
+		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()) {
+			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, areceipts := rawdb.ReadReceipts(fastDb, hash, *rawdb.ReadHeaderNumber(fastDb, hash), fast.Config()), rawdb.ReadReceipts(archiveDb, hash, *rawdb.ReadHeaderNumber(archiveDb, hash), archive.Config()); types.DeriveSha(freceipts) != types.DeriveSha(areceipts) {
-			t.Errorf("block #%d [%x]: receipts mismatch: have %v, want %v", num, hash, freceipts, 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) != types.DeriveSha(areceipts) {
+			t.Errorf("block #%d [%x]: receipts mismatch: fastdb %v, ancientdb %v, archivedb %v", num, hash, freceipts, anreceipts, areceipts)
 		}
 	}
 	// Check that the canonical chains are the same between the databases
 	for i := 0; i < len(blocks)+1; i++ {
 		if fhash, ahash := rawdb.ReadCanonicalHash(fastDb, uint64(i)), rawdb.ReadCanonicalHash(archiveDb, uint64(i)); fhash != ahash {
-			t.Errorf("block #%d: canonical hash mismatch: have %v, want %v", i, fhash, ahash)
+			t.Errorf("block #%d: canonical hash mismatch: fastdb %v, archivedb %v", i, fhash, ahash)
+		}
+		if anhash, arhash := rawdb.ReadCanonicalHash(ancientDb, uint64(i)), rawdb.ReadCanonicalHash(archiveDb, uint64(i)); anhash != arhash {
+			t.Errorf("block #%d: canonical hash mismatch: ancientdb %v, archivedb %v", i, anhash, arhash)
 		}
 	}
 }
@@ -730,13 +760,40 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	if n, err := fast.InsertHeaderChain(headers, 1); err != nil {
 		t.Fatalf("failed to insert header %d: %v", n, err)
 	}
-	if n, err := fast.InsertReceiptChain(blocks, receipts); err != nil {
+	if n, err := fast.InsertReceiptChain(blocks, receipts, 0); err != nil {
 		t.Fatalf("failed to insert receipt %d: %v", n, err)
 	}
 	assert(t, "fast", fast, height, height, 0)
 	fast.Rollback(remove)
 	assert(t, "fast", fast, height/2, height/2, 0)
 
+	// Import the chain as a ancient-first node and ensure all pointers are updated
+	frdir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("failed to create temp freezer dir: %v", err)
+	}
+	defer os.Remove(frdir)
+	ancientDb, err := rawdb.NewDatabaseWithFreezer(rawdb.NewMemoryDatabase(), frdir, "")
+	if err != nil {
+		t.Fatalf("failed to create temp freezer db: %v", err)
+	}
+	gspec.MustCommit(ancientDb)
+	ancient, _ := NewBlockChain(ancientDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{}, nil)
+	defer ancient.Stop()
+
+	if n, err := ancient.InsertHeaderChain(headers, 1); err != nil {
+		t.Fatalf("failed to insert header %d: %v", n, err)
+	}
+	if n, err := ancient.InsertReceiptChain(blocks, receipts, uint64(3*len(blocks)/4)); err != nil {
+		t.Fatalf("failed to insert receipt %d: %v", n, err)
+	}
+	assert(t, "ancient", ancient, height, height, 0)
+	ancient.Rollback(remove)
+	assert(t, "ancient", ancient, height/2, height/2, 0)
+	if frozen, err := ancientDb.Ancients(); err != nil || frozen != height/2+1 {
+		t.Fatalf("failed to truncate ancient store, want %v, have %v", height/2+1, frozen)
+	}
+
 	// Import the chain as a light node and ensure all pointers are updated
 	lightDb := rawdb.NewMemoryDatabase()
 	gspec.MustCommit(lightDb)
@@ -918,7 +975,7 @@ func TestLogRebirth(t *testing.T) {
 	var (
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
-		db      = memorydb.New()
+		db      = rawdb.NewMemoryDatabase()
 
 		// this code generates a log
 		code     = common.Hex2Bytes("60606040525b7f24ec1d3ff24c2f6ff210738839dbc339cd45a5294d85c79361016243157aae7b60405180905060405180910390a15b600a8060416000396000f360606040526008565b00")
@@ -1040,7 +1097,7 @@ func TestSideLogRebirth(t *testing.T) {
 	var (
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
-		db      = memorydb.New()
+		db      = rawdb.NewMemoryDatabase()
 
 		// this code generates a log
 		code     = common.Hex2Bytes("60606040525b7f24ec1d3ff24c2f6ff210738839dbc339cd45a5294d85c79361016243157aae7b60405180905060405180910390a15b600a8060416000396000f360606040526008565b00")
@@ -1564,6 +1621,122 @@ func TestLargeReorgTrieGC(t *testing.T) {
 	}
 }
 
+func TestBlockchainRecovery(t *testing.T) {
+	// Configure and generate a sample block chain
+	var (
+		gendb   = rawdb.NewMemoryDatabase()
+		key, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		address = crypto.PubkeyToAddress(key.PublicKey)
+		funds   = big.NewInt(1000000000)
+		gspec   = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{address: {Balance: funds}}}
+		genesis = gspec.MustCommit(gendb)
+	)
+	height := uint64(1024)
+	blocks, receipts := GenerateChain(gspec.Config, genesis, ethash.NewFaker(), gendb, int(height), nil)
+
+	// Import the chain as a ancient-first node and ensure all pointers are updated
+	frdir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("failed to create temp freezer dir: %v", err)
+	}
+	defer os.Remove(frdir)
+	ancientDb, err := rawdb.NewDatabaseWithFreezer(rawdb.NewMemoryDatabase(), frdir, "")
+	if err != nil {
+		t.Fatalf("failed to create temp freezer db: %v", err)
+	}
+	gspec.MustCommit(ancientDb)
+	ancient, _ := NewBlockChain(ancientDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{}, nil)
+
+	headers := make([]*types.Header, len(blocks))
+	for i, block := range blocks {
+		headers[i] = block.Header()
+	}
+	if n, err := ancient.InsertHeaderChain(headers, 1); err != nil {
+		t.Fatalf("failed to insert header %d: %v", n, err)
+	}
+	if n, err := ancient.InsertReceiptChain(blocks, receipts, uint64(3*len(blocks)/4)); err != nil {
+		t.Fatalf("failed to insert receipt %d: %v", n, err)
+	}
+	ancient.Stop()
+
+	// Destroy head fast block manually
+	midBlock := blocks[len(blocks)/2]
+	rawdb.WriteHeadFastBlockHash(ancientDb, midBlock.Hash())
+
+	// Reopen broken blockchain again
+	ancient, _ = NewBlockChain(ancientDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{}, nil)
+	defer ancient.Stop()
+	if num := ancient.CurrentBlock().NumberU64(); num != 0 {
+		t.Errorf("head block mismatch: have #%v, want #%v", num, 0)
+	}
+	if num := ancient.CurrentFastBlock().NumberU64(); num != midBlock.NumberU64() {
+		t.Errorf("head fast-block mismatch: have #%v, want #%v", num, midBlock.NumberU64())
+	}
+	if num := ancient.CurrentHeader().Number.Uint64(); num != midBlock.NumberU64() {
+		t.Errorf("head header mismatch: have #%v, want #%v", num, midBlock.NumberU64())
+	}
+}
+
+func TestIncompleteAncientReceiptChainInsertion(t *testing.T) {
+	// Configure and generate a sample block chain
+	var (
+		gendb   = rawdb.NewMemoryDatabase()
+		key, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		address = crypto.PubkeyToAddress(key.PublicKey)
+		funds   = big.NewInt(1000000000)
+		gspec   = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{address: {Balance: funds}}}
+		genesis = gspec.MustCommit(gendb)
+	)
+	height := uint64(1024)
+	blocks, receipts := GenerateChain(gspec.Config, genesis, ethash.NewFaker(), gendb, int(height), nil)
+
+	// Import the chain as a ancient-first node and ensure all pointers are updated
+	frdir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("failed to create temp freezer dir: %v", err)
+	}
+	defer os.Remove(frdir)
+	ancientDb, err := rawdb.NewDatabaseWithFreezer(rawdb.NewMemoryDatabase(), frdir, "")
+	if err != nil {
+		t.Fatalf("failed to create temp freezer db: %v", err)
+	}
+	gspec.MustCommit(ancientDb)
+	ancient, _ := NewBlockChain(ancientDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{}, nil)
+	defer ancient.Stop()
+
+	headers := make([]*types.Header, len(blocks))
+	for i, block := range blocks {
+		headers[i] = block.Header()
+	}
+	if n, err := ancient.InsertHeaderChain(headers, 1); err != nil {
+		t.Fatalf("failed to insert header %d: %v", n, err)
+	}
+	// Abort ancient receipt chain insertion deliberately
+	ancient.terminateInsert = func(hash common.Hash, number uint64) bool {
+		if number == blocks[len(blocks)/2].NumberU64() {
+			return true
+		}
+		return false
+	}
+	previousFastBlock := ancient.CurrentFastBlock()
+	if n, err := ancient.InsertReceiptChain(blocks, receipts, uint64(3*len(blocks)/4)); err == nil {
+		t.Fatalf("failed to insert receipt %d: %v", n, err)
+	}
+	if ancient.CurrentFastBlock().NumberU64() != previousFastBlock.NumberU64() {
+		t.Fatalf("failed to rollback ancient data, want %d, have %d", previousFastBlock.NumberU64(), ancient.CurrentFastBlock().NumberU64())
+	}
+	if frozen, err := ancient.db.Ancients(); err != nil || frozen != 1 {
+		t.Fatalf("failed to truncate ancient data")
+	}
+	ancient.terminateInsert = nil
+	if n, err := ancient.InsertReceiptChain(blocks, receipts, uint64(3*len(blocks)/4)); err != nil {
+		t.Fatalf("failed to insert receipt %d: %v", n, err)
+	}
+	if ancient.CurrentFastBlock().NumberU64() != blocks[len(blocks)-1].NumberU64() {
+		t.Fatalf("failed to insert ancient recept chain after rollback")
+	}
+}
+
 // Tests that importing a very large side fork, which is larger than the canon chain,
 // but where the difficulty per block is kept low: this means that it will not
 // overtake the 'canon' chain until after it's passed canon by about 200 blocks.
@@ -1764,7 +1937,7 @@ func testInsertKnownChainData(t *testing.T, typ string) {
 			if err != nil {
 				return err
 			}
-			_, err = chain.InsertReceiptChain(blocks, receipts)
+			_, err = chain.InsertReceiptChain(blocks, receipts, 0)
 			return err
 		}
 		asserter = func(t *testing.T, block *types.Block) {
@@ -2019,14 +2192,12 @@ func BenchmarkBlockChain_1x1000ValueTransferToNonexisting(b *testing.B) {
 		numTxs    = 1000
 		numBlocks = 1
 	)
-
 	recipientFn := func(nonce uint64) common.Address {
 		return common.BigToAddress(big.NewInt(0).SetUint64(1337 + nonce))
 	}
 	dataFn := func(nonce uint64) []byte {
 		return nil
 	}
-
 	benchmarkLargeNumberOfValueToNonexisting(b, numTxs, numBlocks, recipientFn, dataFn)
 }
 
@@ -2044,7 +2215,6 @@ func BenchmarkBlockChain_1x1000ValueTransferToExisting(b *testing.B) {
 	dataFn := func(nonce uint64) []byte {
 		return nil
 	}
-
 	benchmarkLargeNumberOfValueToNonexisting(b, numTxs, numBlocks, recipientFn, dataFn)
 }
 
@@ -2062,6 +2232,5 @@ func BenchmarkBlockChain_1x1000Executions(b *testing.B) {
 	dataFn := func(nonce uint64) []byte {
 		return nil
 	}
-
 	benchmarkLargeNumberOfValueToNonexisting(b, numTxs, numBlocks, recipientFn, dataFn)
 }
diff --git a/core/headerchain.go b/core/headerchain.go
index d0c1987fb..659141fd1 100644
--- a/core/headerchain.go
+++ b/core/headerchain.go
@@ -453,33 +453,56 @@ func (hc *HeaderChain) SetCurrentHeader(head *types.Header) {
 	hc.currentHeaderHash = head.Hash()
 }
 
-// DeleteCallback is a callback function that is called by SetHead before
-// each header is deleted.
-type DeleteCallback func(ethdb.Writer, common.Hash, uint64)
+type (
+	// UpdateHeadBlocksCallback is a callback function that is called by SetHead
+	// before head header is updated.
+	UpdateHeadBlocksCallback func(ethdb.KeyValueWriter, *types.Header)
+
+	// DeleteBlockContentCallback is a callback function that is called by SetHead
+	// before each header is deleted.
+	DeleteBlockContentCallback func(ethdb.KeyValueWriter, common.Hash, uint64)
+)
 
 // SetHead rewinds the local chain to a new head. Everything above the new head
 // will be deleted and the new one set.
-func (hc *HeaderChain) SetHead(head uint64, delFn DeleteCallback) {
-	height := uint64(0)
-
-	if hdr := hc.CurrentHeader(); hdr != nil {
-		height = hdr.Number.Uint64()
-	}
-	batch := hc.chainDb.NewBatch()
+func (hc *HeaderChain) SetHead(head uint64, updateFn UpdateHeadBlocksCallback, delFn DeleteBlockContentCallback) {
+	var (
+		parentHash common.Hash
+		batch      = hc.chainDb.NewBatch()
+	)
 	for hdr := hc.CurrentHeader(); hdr != nil && hdr.Number.Uint64() > head; hdr = hc.CurrentHeader() {
-		hash := hdr.Hash()
-		num := hdr.Number.Uint64()
+		hash, num := hdr.Hash(), hdr.Number.Uint64()
+
+		// Rewind block chain to new head.
+		parent := hc.GetHeader(hdr.ParentHash, num-1)
+		if parent == nil {
+			parent = hc.genesisHeader
+		}
+		parentHash = hdr.ParentHash
+		// Notably, since geth has the possibility for setting the head to a low
+		// height which is even lower than ancient head.
+		// In order to ensure that the head is always no higher than the data in
+		// the database(ancient store or active store), we need to update head
+		// first then remove the relative data from the database.
+		//
+		// Update head first(head fast block, head full block) before deleting the data.
+		if updateFn != nil {
+			updateFn(hc.chainDb, parent)
+		}
+		// Update head header then.
+		rawdb.WriteHeadHeaderHash(hc.chainDb, parentHash)
+
+		// Remove the relative data from the database.
 		if delFn != nil {
 			delFn(batch, hash, num)
 		}
+		// Rewind header chain to new head.
 		rawdb.DeleteHeader(batch, hash, num)
 		rawdb.DeleteTd(batch, hash, num)
+		rawdb.DeleteCanonicalHash(batch, num)
 
-		hc.currentHeader.Store(hc.GetHeader(hdr.ParentHash, hdr.Number.Uint64()-1))
-	}
-	// Roll back the canonical chain numbering
-	for i := height; i > head; i-- {
-		rawdb.DeleteCanonicalHash(batch, i)
+		hc.currentHeader.Store(parent)
+		hc.currentHeaderHash = parentHash
 	}
 	batch.Write()
 
@@ -487,13 +510,6 @@ func (hc *HeaderChain) SetHead(head uint64, delFn DeleteCallback) {
 	hc.headerCache.Purge()
 	hc.tdCache.Purge()
 	hc.numberCache.Purge()
-
-	if hc.CurrentHeader() == nil {
-		hc.currentHeader.Store(hc.genesisHeader)
-	}
-	hc.currentHeaderHash = hc.CurrentHeader().Hash()
-
-	rawdb.WriteHeadHeaderHash(hc.chainDb, hc.currentHeaderHash)
 }
 
 // SetGenesis sets a new genesis block header for the chain
diff --git a/core/rawdb/accessors_chain.go b/core/rawdb/accessors_chain.go
index 103f18f78..681e6e917 100644
--- a/core/rawdb/accessors_chain.go
+++ b/core/rawdb/accessors_chain.go
@@ -30,10 +30,17 @@ import (
 )
 
 // ReadCanonicalHash retrieves the hash assigned to a canonical block number.
-func ReadCanonicalHash(db ethdb.AncientReader, number uint64) common.Hash {
-	data, _ := db.Ancient("hashes", number)
+func ReadCanonicalHash(db ethdb.Reader, number uint64) common.Hash {
+	data, _ := db.Ancient(freezerHashTable, number)
 	if len(data) == 0 {
 		data, _ = db.Get(headerHashKey(number))
+		// In the background freezer is moving data from leveldb to flatten files.
+		// So during the first check for ancient db, the data is not yet in there,
+		// but when we reach into leveldb, the data was already moved. That would
+		// result in a not found error.
+		if len(data) == 0 {
+			data, _ = db.Ancient(freezerHashTable, number)
+		}
 	}
 	if len(data) == 0 {
 		return common.Hash{}
@@ -42,29 +49,28 @@ func ReadCanonicalHash(db ethdb.AncientReader, number uint64) common.Hash {
 }
 
 // WriteCanonicalHash stores the hash assigned to a canonical block number.
-func WriteCanonicalHash(db ethdb.Writer, hash common.Hash, number uint64) {
+func WriteCanonicalHash(db ethdb.KeyValueWriter, hash common.Hash, number uint64) {
 	if err := db.Put(headerHashKey(number), hash.Bytes()); err != nil {
 		log.Crit("Failed to store number to hash mapping", "err", err)
 	}
 }
 
 // DeleteCanonicalHash removes the number to hash canonical mapping.
-func DeleteCanonicalHash(db ethdb.Writer, number uint64) {
+func DeleteCanonicalHash(db ethdb.KeyValueWriter, number uint64) {
 	if err := db.Delete(headerHashKey(number)); err != nil {
 		log.Crit("Failed to delete number to hash mapping", "err", err)
 	}
 }
 
-// readAllHashes retrieves all the hashes assigned to blocks at a certain heights,
+// ReadAllHashes retrieves all the hashes assigned to blocks at a certain heights,
 // both canonical and reorged forks included.
-//
-// This method is a helper for the chain reader. It should never be exposed to the
-// outside world.
-func readAllHashes(db ethdb.Iteratee, number uint64) []common.Hash {
+func ReadAllHashes(db ethdb.Iteratee, number uint64) []common.Hash {
 	prefix := headerKeyPrefix(number)
 
 	hashes := make([]common.Hash, 0, 1)
 	it := db.NewIteratorWithPrefix(prefix)
+	defer it.Release()
+
 	for it.Next() {
 		if key := it.Key(); len(key) == len(prefix)+32 {
 			hashes = append(hashes, common.BytesToHash(key[len(key)-32:]))
@@ -74,7 +80,7 @@ func readAllHashes(db ethdb.Iteratee, number uint64) []common.Hash {
 }
 
 // ReadHeaderNumber returns the header number assigned to a hash.
-func ReadHeaderNumber(db ethdb.Reader, hash common.Hash) *uint64 {
+func ReadHeaderNumber(db ethdb.KeyValueReader, hash common.Hash) *uint64 {
 	data, _ := db.Get(headerNumberKey(hash))
 	if len(data) != 8 {
 		return nil
@@ -83,8 +89,15 @@ func ReadHeaderNumber(db ethdb.Reader, hash common.Hash) *uint64 {
 	return &number
 }
 
+// DeleteHeaderNumber removes hash to number mapping.
+func DeleteHeaderNumber(db ethdb.KeyValueWriter, hash common.Hash) {
+	if err := db.Delete(headerNumberKey(hash)); err != nil {
+		log.Crit("Failed to delete hash to number mapping", "err", err)
+	}
+}
+
 // ReadHeadHeaderHash retrieves the hash of the current canonical head header.
-func ReadHeadHeaderHash(db ethdb.Reader) common.Hash {
+func ReadHeadHeaderHash(db ethdb.KeyValueReader) common.Hash {
 	data, _ := db.Get(headHeaderKey)
 	if len(data) == 0 {
 		return common.Hash{}
@@ -93,14 +106,14 @@ func ReadHeadHeaderHash(db ethdb.Reader) common.Hash {
 }
 
 // WriteHeadHeaderHash stores the hash of the current canonical head header.
-func WriteHeadHeaderHash(db ethdb.Writer, hash common.Hash) {
+func WriteHeadHeaderHash(db ethdb.KeyValueWriter, hash common.Hash) {
 	if err := db.Put(headHeaderKey, hash.Bytes()); err != nil {
 		log.Crit("Failed to store last header's hash", "err", err)
 	}
 }
 
 // ReadHeadBlockHash retrieves the hash of the current canonical head block.
-func ReadHeadBlockHash(db ethdb.Reader) common.Hash {
+func ReadHeadBlockHash(db ethdb.KeyValueReader) common.Hash {
 	data, _ := db.Get(headBlockKey)
 	if len(data) == 0 {
 		return common.Hash{}
@@ -109,14 +122,14 @@ func ReadHeadBlockHash(db ethdb.Reader) common.Hash {
 }
 
 // WriteHeadBlockHash stores the head block's hash.
-func WriteHeadBlockHash(db ethdb.Writer, hash common.Hash) {
+func WriteHeadBlockHash(db ethdb.KeyValueWriter, hash common.Hash) {
 	if err := db.Put(headBlockKey, hash.Bytes()); err != nil {
 		log.Crit("Failed to store last block's hash", "err", err)
 	}
 }
 
 // ReadHeadFastBlockHash retrieves the hash of the current fast-sync head block.
-func ReadHeadFastBlockHash(db ethdb.Reader) common.Hash {
+func ReadHeadFastBlockHash(db ethdb.KeyValueReader) common.Hash {
 	data, _ := db.Get(headFastBlockKey)
 	if len(data) == 0 {
 		return common.Hash{}
@@ -125,7 +138,7 @@ func ReadHeadFastBlockHash(db ethdb.Reader) common.Hash {
 }
 
 // WriteHeadFastBlockHash stores the hash of the current fast-sync head block.
-func WriteHeadFastBlockHash(db ethdb.Writer, hash common.Hash) {
+func WriteHeadFastBlockHash(db ethdb.KeyValueWriter, hash common.Hash) {
 	if err := db.Put(headFastBlockKey, hash.Bytes()); err != nil {
 		log.Crit("Failed to store last fast block's hash", "err", err)
 	}
@@ -133,7 +146,7 @@ func WriteHeadFastBlockHash(db ethdb.Writer, hash common.Hash) {
 
 // ReadFastTrieProgress retrieves the number of tries nodes fast synced to allow
 // reporting correct numbers across restarts.
-func ReadFastTrieProgress(db ethdb.Reader) uint64 {
+func ReadFastTrieProgress(db ethdb.KeyValueReader) uint64 {
 	data, _ := db.Get(fastTrieProgressKey)
 	if len(data) == 0 {
 		return 0
@@ -143,24 +156,31 @@ func ReadFastTrieProgress(db ethdb.Reader) uint64 {
 
 // WriteFastTrieProgress stores the fast sync trie process counter to support
 // retrieving it across restarts.
-func WriteFastTrieProgress(db ethdb.Writer, count uint64) {
+func WriteFastTrieProgress(db ethdb.KeyValueWriter, count uint64) {
 	if err := db.Put(fastTrieProgressKey, new(big.Int).SetUint64(count).Bytes()); err != nil {
 		log.Crit("Failed to store fast sync trie progress", "err", err)
 	}
 }
 
 // ReadHeaderRLP retrieves a block header in its raw RLP database encoding.
-func ReadHeaderRLP(db ethdb.AncientReader, hash common.Hash, number uint64) rlp.RawValue {
-	data, _ := db.Ancient("headers", number)
+func ReadHeaderRLP(db ethdb.Reader, hash common.Hash, number uint64) rlp.RawValue {
+	data, _ := db.Ancient(freezerHeaderTable, number)
 	if len(data) == 0 {
 		data, _ = db.Get(headerKey(number, hash))
+		// In the background freezer is moving data from leveldb to flatten files.
+		// So during the first check for ancient db, the data is not yet in there,
+		// but when we reach into leveldb, the data was already moved. That would
+		// result in a not found error.
+		if len(data) == 0 {
+			data, _ = db.Ancient(freezerHeaderTable, number)
+		}
 	}
 	return data
 }
 
 // HasHeader verifies the existence of a block header corresponding to the hash.
-func HasHeader(db ethdb.AncientReader, hash common.Hash, number uint64) bool {
-	if has, err := db.Ancient("hashes", number); err == nil && common.BytesToHash(has) == hash {
+func HasHeader(db ethdb.Reader, hash common.Hash, number uint64) bool {
+	if has, err := db.Ancient(freezerHashTable, number); err == nil && common.BytesToHash(has) == hash {
 		return true
 	}
 	if has, err := db.Has(headerKey(number, hash)); !has || err != nil {
@@ -170,7 +190,7 @@ func HasHeader(db ethdb.AncientReader, hash common.Hash, number uint64) bool {
 }
 
 // ReadHeader retrieves the block header corresponding to the hash.
-func ReadHeader(db ethdb.AncientReader, hash common.Hash, number uint64) *types.Header {
+func ReadHeader(db ethdb.Reader, hash common.Hash, number uint64) *types.Header {
 	data := ReadHeaderRLP(db, hash, number)
 	if len(data) == 0 {
 		return nil
@@ -185,7 +205,7 @@ func ReadHeader(db ethdb.AncientReader, hash common.Hash, number uint64) *types.
 
 // WriteHeader stores a block header into the database and also stores the hash-
 // to-number mapping.
-func WriteHeader(db ethdb.Writer, header *types.Header) {
+func WriteHeader(db ethdb.KeyValueWriter, header *types.Header) {
 	// Write the hash -> number mapping
 	var (
 		hash    = header.Hash()
@@ -208,7 +228,7 @@ func WriteHeader(db ethdb.Writer, header *types.Header) {
 }
 
 // DeleteHeader removes all block header data associated with a hash.
-func DeleteHeader(db ethdb.Writer, hash common.Hash, number uint64) {
+func DeleteHeader(db ethdb.KeyValueWriter, hash common.Hash, number uint64) {
 	deleteHeaderWithoutNumber(db, hash, number)
 	if err := db.Delete(headerNumberKey(hash)); err != nil {
 		log.Crit("Failed to delete hash to number mapping", "err", err)
@@ -217,31 +237,38 @@ func DeleteHeader(db ethdb.Writer, hash common.Hash, number uint64) {
 
 // deleteHeaderWithoutNumber removes only the block header but does not remove
 // the hash to number mapping.
-func deleteHeaderWithoutNumber(db ethdb.Writer, hash common.Hash, number uint64) {
+func deleteHeaderWithoutNumber(db ethdb.KeyValueWriter, hash common.Hash, number uint64) {
 	if err := db.Delete(headerKey(number, hash)); err != nil {
 		log.Crit("Failed to delete header", "err", err)
 	}
 }
 
 // ReadBodyRLP retrieves the block body (transactions and uncles) in RLP encoding.
-func ReadBodyRLP(db ethdb.AncientReader, hash common.Hash, number uint64) rlp.RawValue {
-	data, _ := db.Ancient("bodies", number)
+func ReadBodyRLP(db ethdb.Reader, hash common.Hash, number uint64) rlp.RawValue {
+	data, _ := db.Ancient(freezerBodiesTable, number)
 	if len(data) == 0 {
 		data, _ = db.Get(blockBodyKey(number, hash))
+		// In the background freezer is moving data from leveldb to flatten files.
+		// So during the first check for ancient db, the data is not yet in there,
+		// but when we reach into leveldb, the data was already moved. That would
+		// result in a not found error.
+		if len(data) == 0 {
+			data, _ = db.Ancient(freezerBodiesTable, number)
+		}
 	}
 	return data
 }
 
 // WriteBodyRLP stores an RLP encoded block body into the database.
-func WriteBodyRLP(db ethdb.Writer, hash common.Hash, number uint64, rlp rlp.RawValue) {
+func WriteBodyRLP(db ethdb.KeyValueWriter, hash common.Hash, number uint64, rlp rlp.RawValue) {
 	if err := db.Put(blockBodyKey(number, hash), rlp); err != nil {
 		log.Crit("Failed to store block body", "err", err)
 	}
 }
 
 // HasBody verifies the existence of a block body corresponding to the hash.
-func HasBody(db ethdb.AncientReader, hash common.Hash, number uint64) bool {
-	if has, err := db.Ancient("hashes", number); err == nil && common.BytesToHash(has) == hash {
+func HasBody(db ethdb.Reader, hash common.Hash, number uint64) bool {
+	if has, err := db.Ancient(freezerHashTable, number); err == nil && common.BytesToHash(has) == hash {
 		return true
 	}
 	if has, err := db.Has(blockBodyKey(number, hash)); !has || err != nil {
@@ -251,7 +278,7 @@ func HasBody(db ethdb.AncientReader, hash common.Hash, number uint64) bool {
 }
 
 // ReadBody retrieves the block body corresponding to the hash.
-func ReadBody(db ethdb.AncientReader, hash common.Hash, number uint64) *types.Body {
+func ReadBody(db ethdb.Reader, hash common.Hash, number uint64) *types.Body {
 	data := ReadBodyRLP(db, hash, number)
 	if len(data) == 0 {
 		return nil
@@ -265,7 +292,7 @@ func ReadBody(db ethdb.AncientReader, hash common.Hash, number uint64) *types.Bo
 }
 
 // WriteBody stores a block body into the database.
-func WriteBody(db ethdb.Writer, hash common.Hash, number uint64, body *types.Body) {
+func WriteBody(db ethdb.KeyValueWriter, hash common.Hash, number uint64, body *types.Body) {
 	data, err := rlp.EncodeToBytes(body)
 	if err != nil {
 		log.Crit("Failed to RLP encode body", "err", err)
@@ -274,23 +301,30 @@ func WriteBody(db ethdb.Writer, hash common.Hash, number uint64, body *types.Bod
 }
 
 // DeleteBody removes all block body data associated with a hash.
-func DeleteBody(db ethdb.Writer, hash common.Hash, number uint64) {
+func DeleteBody(db ethdb.KeyValueWriter, hash common.Hash, number uint64) {
 	if err := db.Delete(blockBodyKey(number, hash)); err != nil {
 		log.Crit("Failed to delete block body", "err", err)
 	}
 }
 
 // ReadTdRLP retrieves a block's total difficulty corresponding to the hash in RLP encoding.
-func ReadTdRLP(db ethdb.AncientReader, hash common.Hash, number uint64) rlp.RawValue {
-	data, _ := db.Ancient("diffs", number)
+func ReadTdRLP(db ethdb.Reader, hash common.Hash, number uint64) rlp.RawValue {
+	data, _ := db.Ancient(freezerDifficultyTable, number)
 	if len(data) == 0 {
 		data, _ = db.Get(headerTDKey(number, hash))
+		// In the background freezer is moving data from leveldb to flatten files.
+		// So during the first check for ancient db, the data is not yet in there,
+		// but when we reach into leveldb, the data was already moved. That would
+		// result in a not found error.
+		if len(data) == 0 {
+			data, _ = db.Ancient(freezerDifficultyTable, number)
+		}
 	}
 	return data
 }
 
 // ReadTd retrieves a block's total difficulty corresponding to the hash.
-func ReadTd(db ethdb.AncientReader, hash common.Hash, number uint64) *big.Int {
+func ReadTd(db ethdb.Reader, hash common.Hash, number uint64) *big.Int {
 	data := ReadTdRLP(db, hash, number)
 	if len(data) == 0 {
 		return nil
@@ -304,7 +338,7 @@ func ReadTd(db ethdb.AncientReader, hash common.Hash, number uint64) *big.Int {
 }
 
 // WriteTd stores the total difficulty of a block into the database.
-func WriteTd(db ethdb.Writer, hash common.Hash, number uint64, td *big.Int) {
+func WriteTd(db ethdb.KeyValueWriter, hash common.Hash, number uint64, td *big.Int) {
 	data, err := rlp.EncodeToBytes(td)
 	if err != nil {
 		log.Crit("Failed to RLP encode block total difficulty", "err", err)
@@ -315,7 +349,7 @@ func WriteTd(db ethdb.Writer, hash common.Hash, number uint64, td *big.Int) {
 }
 
 // DeleteTd removes all block total difficulty data associated with a hash.
-func DeleteTd(db ethdb.Writer, hash common.Hash, number uint64) {
+func DeleteTd(db ethdb.KeyValueWriter, hash common.Hash, number uint64) {
 	if err := db.Delete(headerTDKey(number, hash)); err != nil {
 		log.Crit("Failed to delete block total difficulty", "err", err)
 	}
@@ -323,8 +357,8 @@ func DeleteTd(db ethdb.Writer, hash common.Hash, number uint64) {
 
 // HasReceipts verifies the existence of all the transaction receipts belonging
 // to a block.
-func HasReceipts(db ethdb.AncientReader, hash common.Hash, number uint64) bool {
-	if has, err := db.Ancient("hashes", number); err == nil && common.BytesToHash(has) == hash {
+func HasReceipts(db ethdb.Reader, hash common.Hash, number uint64) bool {
+	if has, err := db.Ancient(freezerHashTable, number); err == nil && common.BytesToHash(has) == hash {
 		return true
 	}
 	if has, err := db.Has(blockReceiptsKey(number, hash)); !has || err != nil {
@@ -334,10 +368,17 @@ func HasReceipts(db ethdb.AncientReader, hash common.Hash, number uint64) bool {
 }
 
 // ReadReceiptsRLP retrieves all the transaction receipts belonging to a block in RLP encoding.
-func ReadReceiptsRLP(db ethdb.AncientReader, hash common.Hash, number uint64) rlp.RawValue {
-	data, _ := db.Ancient("receipts", number)
+func ReadReceiptsRLP(db ethdb.Reader, hash common.Hash, number uint64) rlp.RawValue {
+	data, _ := db.Ancient(freezerReceiptTable, number)
 	if len(data) == 0 {
 		data, _ = db.Get(blockReceiptsKey(number, hash))
+		// In the background freezer is moving data from leveldb to flatten files.
+		// So during the first check for ancient db, the data is not yet in there,
+		// but when we reach into leveldb, the data was already moved. That would
+		// result in a not found error.
+		if len(data) == 0 {
+			data, _ = db.Ancient(freezerReceiptTable, number)
+		}
 	}
 	return data
 }
@@ -345,7 +386,7 @@ func ReadReceiptsRLP(db ethdb.AncientReader, hash common.Hash, number uint64) rl
 // ReadRawReceipts retrieves all the transaction receipts belonging to a block.
 // The receipt metadata fields are not guaranteed to be populated, so they
 // should not be used. Use ReadReceipts instead if the metadata is needed.
-func ReadRawReceipts(db ethdb.AncientReader, hash common.Hash, number uint64) types.Receipts {
+func ReadRawReceipts(db ethdb.Reader, hash common.Hash, number uint64) types.Receipts {
 	// Retrieve the flattened receipt slice
 	data := ReadReceiptsRLP(db, hash, number)
 	if len(data) == 0 {
@@ -371,7 +412,7 @@ func ReadRawReceipts(db ethdb.AncientReader, hash common.Hash, number uint64) ty
 // The current implementation populates these metadata fields by reading the receipts'
 // corresponding block body, so if the block body is not found it will return nil even
 // if the receipt itself is stored.
-func ReadReceipts(db ethdb.AncientReader, hash common.Hash, number uint64, config *params.ChainConfig) types.Receipts {
+func ReadReceipts(db ethdb.Reader, hash common.Hash, number uint64, config *params.ChainConfig) types.Receipts {
 	// We're deriving many fields from the block body, retrieve beside the receipt
 	receipts := ReadRawReceipts(db, hash, number)
 	if receipts == nil {
@@ -390,7 +431,7 @@ func ReadReceipts(db ethdb.AncientReader, hash common.Hash, number uint64, confi
 }
 
 // WriteReceipts stores all the transaction receipts belonging to a block.
-func WriteReceipts(db ethdb.Writer, hash common.Hash, number uint64, receipts types.Receipts) {
+func WriteReceipts(db ethdb.KeyValueWriter, hash common.Hash, number uint64, receipts types.Receipts) {
 	// Convert the receipts into their storage form and serialize them
 	storageReceipts := make([]*types.ReceiptForStorage, len(receipts))
 	for i, receipt := range receipts {
@@ -407,7 +448,7 @@ func WriteReceipts(db ethdb.Writer, hash common.Hash, number uint64, receipts ty
 }
 
 // DeleteReceipts removes all receipt data associated with a block hash.
-func DeleteReceipts(db ethdb.Writer, hash common.Hash, number uint64) {
+func DeleteReceipts(db ethdb.KeyValueWriter, hash common.Hash, number uint64) {
 	if err := db.Delete(blockReceiptsKey(number, hash)); err != nil {
 		log.Crit("Failed to delete block receipts", "err", err)
 	}
@@ -419,7 +460,7 @@ func DeleteReceipts(db ethdb.Writer, hash common.Hash, number uint64) {
 //
 // Note, due to concurrent download of header and block body the header and thus
 // canonical hash can be stored in the database but the body data not (yet).
-func ReadBlock(db ethdb.AncientReader, hash common.Hash, number uint64) *types.Block {
+func ReadBlock(db ethdb.Reader, hash common.Hash, number uint64) *types.Block {
 	header := ReadHeader(db, hash, number)
 	if header == nil {
 		return nil
@@ -432,22 +473,53 @@ func ReadBlock(db ethdb.AncientReader, hash common.Hash, number uint64) *types.B
 }
 
 // WriteBlock serializes a block into the database, header and body separately.
-func WriteBlock(db ethdb.Writer, block *types.Block) {
+func WriteBlock(db ethdb.KeyValueWriter, block *types.Block) {
 	WriteBody(db, block.Hash(), block.NumberU64(), block.Body())
 	WriteHeader(db, block.Header())
 }
 
+// WriteAncientBlock writes entire block data into ancient store and returns the total written size.
+func WriteAncientBlock(db ethdb.AncientWriter, block *types.Block, receipts types.Receipts, td *big.Int) int {
+	// Encode all block components to RLP format.
+	headerBlob, err := rlp.EncodeToBytes(block.Header())
+	if err != nil {
+		log.Crit("Failed to RLP encode block header", "err", err)
+	}
+	bodyBlob, err := rlp.EncodeToBytes(block.Body())
+	if err != nil {
+		log.Crit("Failed to RLP encode body", "err", err)
+	}
+	storageReceipts := make([]*types.ReceiptForStorage, len(receipts))
+	for i, receipt := range receipts {
+		storageReceipts[i] = (*types.ReceiptForStorage)(receipt)
+	}
+	receiptBlob, err := rlp.EncodeToBytes(storageReceipts)
+	if err != nil {
+		log.Crit("Failed to RLP encode block receipts", "err", err)
+	}
+	tdBlob, err := rlp.EncodeToBytes(td)
+	if err != nil {
+		log.Crit("Failed to RLP encode block total difficulty", "err", err)
+	}
+	// Write all blob to flatten files.
+	err = db.AppendAncient(block.NumberU64(), block.Hash().Bytes(), headerBlob, bodyBlob, receiptBlob, tdBlob)
+	if err != nil {
+		log.Crit("Failed to write block data to ancient store", "err", err)
+	}
+	return len(headerBlob) + len(bodyBlob) + len(receiptBlob) + len(tdBlob) + common.HashLength
+}
+
 // DeleteBlock removes all block data associated with a hash.
-func DeleteBlock(db ethdb.Writer, hash common.Hash, number uint64) {
+func DeleteBlock(db ethdb.KeyValueWriter, hash common.Hash, number uint64) {
 	DeleteReceipts(db, hash, number)
 	DeleteHeader(db, hash, number)
 	DeleteBody(db, hash, number)
 	DeleteTd(db, hash, number)
 }
 
-// deleteBlockWithoutNumber removes all block data associated with a hash, except
+// DeleteBlockWithoutNumber removes all block data associated with a hash, except
 // the hash to number mapping.
-func deleteBlockWithoutNumber(db ethdb.Writer, hash common.Hash, number uint64) {
+func DeleteBlockWithoutNumber(db ethdb.KeyValueWriter, hash common.Hash, number uint64) {
 	DeleteReceipts(db, hash, number)
 	deleteHeaderWithoutNumber(db, hash, number)
 	DeleteBody(db, hash, number)
@@ -455,7 +527,7 @@ func deleteBlockWithoutNumber(db ethdb.Writer, hash common.Hash, number uint64)
 }
 
 // FindCommonAncestor returns the last common ancestor of two block headers
-func FindCommonAncestor(db ethdb.AncientReader, a, b *types.Header) *types.Header {
+func FindCommonAncestor(db ethdb.Reader, a, b *types.Header) *types.Header {
 	for bn := b.Number.Uint64(); a.Number.Uint64() > bn; {
 		a = ReadHeader(db, a.ParentHash, a.Number.Uint64()-1)
 		if a == nil {
diff --git a/core/rawdb/accessors_indexes.go b/core/rawdb/accessors_indexes.go
index 666e3edff..ed1f1bca6 100644
--- a/core/rawdb/accessors_indexes.go
+++ b/core/rawdb/accessors_indexes.go
@@ -54,7 +54,7 @@ func ReadTxLookupEntry(db ethdb.Reader, hash common.Hash) *uint64 {
 
 // WriteTxLookupEntries stores a positional metadata for every transaction from
 // a block, enabling hash based transaction and receipt lookups.
-func WriteTxLookupEntries(db ethdb.Writer, block *types.Block) {
+func WriteTxLookupEntries(db ethdb.KeyValueWriter, block *types.Block) {
 	for _, tx := range block.Transactions() {
 		if err := db.Put(txLookupKey(tx.Hash()), block.Number().Bytes()); err != nil {
 			log.Crit("Failed to store transaction lookup entry", "err", err)
@@ -63,13 +63,13 @@ func WriteTxLookupEntries(db ethdb.Writer, block *types.Block) {
 }
 
 // DeleteTxLookupEntry removes all transaction data associated with a hash.
-func DeleteTxLookupEntry(db ethdb.Writer, hash common.Hash) {
+func DeleteTxLookupEntry(db ethdb.KeyValueWriter, hash common.Hash) {
 	db.Delete(txLookupKey(hash))
 }
 
 // ReadTransaction retrieves a specific transaction from the database, along with
 // its added positional metadata.
-func ReadTransaction(db ethdb.AncientReader, hash common.Hash) (*types.Transaction, common.Hash, uint64, uint64) {
+func ReadTransaction(db ethdb.Reader, hash common.Hash) (*types.Transaction, common.Hash, uint64, uint64) {
 	blockNumber := ReadTxLookupEntry(db, hash)
 	if blockNumber == nil {
 		return nil, common.Hash{}, 0, 0
@@ -94,7 +94,7 @@ func ReadTransaction(db ethdb.AncientReader, hash common.Hash) (*types.Transacti
 
 // ReadReceipt retrieves a specific transaction receipt from the database, along with
 // its added positional metadata.
-func ReadReceipt(db ethdb.AncientReader, hash common.Hash, config *params.ChainConfig) (*types.Receipt, common.Hash, uint64, uint64) {
+func ReadReceipt(db ethdb.Reader, hash common.Hash, config *params.ChainConfig) (*types.Receipt, common.Hash, uint64, uint64) {
 	// Retrieve the context of the receipt based on the transaction hash
 	blockNumber := ReadTxLookupEntry(db, hash)
 	if blockNumber == nil {
@@ -117,13 +117,13 @@ func ReadReceipt(db ethdb.AncientReader, hash common.Hash, config *params.ChainC
 
 // ReadBloomBits retrieves the compressed bloom bit vector belonging to the given
 // section and bit index from the.
-func ReadBloomBits(db ethdb.Reader, bit uint, section uint64, head common.Hash) ([]byte, error) {
+func ReadBloomBits(db ethdb.KeyValueReader, bit uint, section uint64, head common.Hash) ([]byte, error) {
 	return db.Get(bloomBitsKey(bit, section, head))
 }
 
 // WriteBloomBits stores the compressed bloom bits vector belonging to the given
 // section and bit index.
-func WriteBloomBits(db ethdb.Writer, bit uint, section uint64, head common.Hash, bits []byte) {
+func WriteBloomBits(db ethdb.KeyValueWriter, bit uint, section uint64, head common.Hash, bits []byte) {
 	if err := db.Put(bloomBitsKey(bit, section, head), bits); err != nil {
 		log.Crit("Failed to store bloom bits", "err", err)
 	}
diff --git a/core/rawdb/accessors_metadata.go b/core/rawdb/accessors_metadata.go
index 1361b0d73..f8d09fbdd 100644
--- a/core/rawdb/accessors_metadata.go
+++ b/core/rawdb/accessors_metadata.go
@@ -27,7 +27,7 @@ import (
 )
 
 // ReadDatabaseVersion retrieves the version number of the database.
-func ReadDatabaseVersion(db ethdb.Reader) *uint64 {
+func ReadDatabaseVersion(db ethdb.KeyValueReader) *uint64 {
 	var version uint64
 
 	enc, _ := db.Get(databaseVerisionKey)
@@ -42,7 +42,7 @@ func ReadDatabaseVersion(db ethdb.Reader) *uint64 {
 }
 
 // WriteDatabaseVersion stores the version number of the database
-func WriteDatabaseVersion(db ethdb.Writer, version uint64) {
+func WriteDatabaseVersion(db ethdb.KeyValueWriter, version uint64) {
 	enc, err := rlp.EncodeToBytes(version)
 	if err != nil {
 		log.Crit("Failed to encode database version", "err", err)
@@ -53,7 +53,7 @@ func WriteDatabaseVersion(db ethdb.Writer, version uint64) {
 }
 
 // ReadChainConfig retrieves the consensus settings based on the given genesis hash.
-func ReadChainConfig(db ethdb.Reader, hash common.Hash) *params.ChainConfig {
+func ReadChainConfig(db ethdb.KeyValueReader, hash common.Hash) *params.ChainConfig {
 	data, _ := db.Get(configKey(hash))
 	if len(data) == 0 {
 		return nil
@@ -67,7 +67,7 @@ func ReadChainConfig(db ethdb.Reader, hash common.Hash) *params.ChainConfig {
 }
 
 // WriteChainConfig writes the chain config settings to the database.
-func WriteChainConfig(db ethdb.Writer, hash common.Hash, cfg *params.ChainConfig) {
+func WriteChainConfig(db ethdb.KeyValueWriter, hash common.Hash, cfg *params.ChainConfig) {
 	if cfg == nil {
 		return
 	}
@@ -81,13 +81,13 @@ func WriteChainConfig(db ethdb.Writer, hash common.Hash, cfg *params.ChainConfig
 }
 
 // ReadPreimage retrieves a single preimage of the provided hash.
-func ReadPreimage(db ethdb.Reader, hash common.Hash) []byte {
+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.Writer, preimages map[common.Hash][]byte) {
+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)
diff --git a/core/rawdb/database.go b/core/rawdb/database.go
index cd1048cbc..5a3c7f94b 100644
--- a/core/rawdb/database.go
+++ b/core/rawdb/database.go
@@ -24,7 +24,7 @@ import (
 	"github.com/ethereum/go-ethereum/ethdb/memorydb"
 )
 
-// freezerdb is a databse wrapper that enabled freezer data retrievals.
+// freezerdb is a database wrapper that enabled freezer data retrievals.
 type freezerdb struct {
 	ethdb.KeyValueStore
 	ethdb.AncientStore
@@ -51,9 +51,34 @@ type nofreezedb struct {
 	ethdb.KeyValueStore
 }
 
-// Frozen returns nil as we don't have a backing chain freezer.
+// HasAncient returns an error as we don't have a backing chain freezer.
+func (db *nofreezedb) HasAncient(kind string, number uint64) (bool, error) {
+	return false, errNotSupported
+}
+
+// Ancient returns an error as we don't have a backing chain freezer.
 func (db *nofreezedb) Ancient(kind string, number uint64) ([]byte, error) {
-	return nil, errOutOfBounds
+	return nil, errNotSupported
+}
+
+// Ancients returns an error as we don't have a backing chain freezer.
+func (db *nofreezedb) Ancients() (uint64, error) {
+	return 0, errNotSupported
+}
+
+// AppendAncient returns an error as we don't have a backing chain freezer.
+func (db *nofreezedb) AppendAncient(number uint64, hash, header, body, receipts, td []byte) error {
+	return errNotSupported
+}
+
+// TruncateAncients returns an error as we don't have a backing chain freezer.
+func (db *nofreezedb) TruncateAncients(items uint64) error {
+	return errNotSupported
+}
+
+// Sync returns an error as we don't have a backing chain freezer.
+func (db *nofreezedb) Sync() error {
+	return errNotSupported
 }
 
 // NewDatabase creates a high level database on top of a given key-value data
diff --git a/core/rawdb/freezer.go b/core/rawdb/freezer.go
index 07df4c759..84426d8ae 100644
--- a/core/rawdb/freezer.go
+++ b/core/rawdb/freezer.go
@@ -31,9 +31,15 @@ import (
 	"github.com/prometheus/tsdb/fileutil"
 )
 
-// errUnknownTable is returned if the user attempts to read from a table that is
-// not tracked by the freezer.
-var errUnknownTable = errors.New("unknown table")
+var (
+	// errUnknownTable is returned if the user attempts to read from a table that is
+	// not tracked by the freezer.
+	errUnknownTable = errors.New("unknown table")
+
+	// errOutOrderInsertion is returned if the user attempts to inject out-of-order
+	// binary blobs into the freezer.
+	errOutOrderInsertion = errors.New("the append operation is out-order")
+)
 
 const (
 	// freezerRecheckInterval is the frequency to check the key-value database for
@@ -44,7 +50,7 @@ const (
 	// freezerBlockGraduation is the number of confirmations a block must achieve
 	// before it becomes elligible for chain freezing. This must exceed any chain
 	// reorg depth, since the freezer also deletes all block siblings.
-	freezerBlockGraduation = 60000
+	freezerBlockGraduation = 90000
 
 	// freezerBatchLimit is the maximum number of blocks to freeze in one batch
 	// before doing an fsync and deleting it from the key-value store.
@@ -72,7 +78,9 @@ func newFreezer(datadir string, namespace string) (*freezer, error) {
 		readMeter  = metrics.NewRegisteredMeter(namespace+"ancient/read", nil)
 		writeMeter = metrics.NewRegisteredMeter(namespace+"ancient/write", nil)
 	)
-	lock, _, err := fileutil.Flock(filepath.Join(datadir, "LOCK"))
+	// Leveldb uses LOCK as the filelock filename. To prevent the
+	// name collision, we use FLOCK as the lock name.
+	lock, _, err := fileutil.Flock(filepath.Join(datadir, "FLOCK"))
 	if err != nil {
 		return nil, err
 	}
@@ -81,7 +89,7 @@ func newFreezer(datadir string, namespace string) (*freezer, error) {
 		tables:       make(map[string]*freezerTable),
 		instanceLock: lock,
 	}
-	for _, name := range []string{"hashes", "headers", "bodies", "receipts", "diffs"} {
+	for _, name := range []string{freezerHashTable, freezerHeaderTable, freezerBodiesTable, freezerReceiptTable, freezerDifficultyTable} {
 		table, err := newTable(datadir, name, readMeter, writeMeter)
 		if err != nil {
 			for _, table := range freezer.tables {
@@ -92,21 +100,12 @@ func newFreezer(datadir string, namespace string) (*freezer, error) {
 		}
 		freezer.tables[name] = table
 	}
-	// Truncate all data tables to the same length
-	freezer.frozen = math.MaxUint64
-	for _, table := range freezer.tables {
-		if freezer.frozen > table.items {
-			freezer.frozen = table.items
-		}
-	}
-	for _, table := range freezer.tables {
-		if err := table.truncate(freezer.frozen); err != nil {
-			for _, table := range freezer.tables {
-				table.Close()
-			}
-			lock.Release()
-			return nil, err
+	if err := freezer.repair(); err != nil {
+		for _, table := range freezer.tables {
+			table.Close()
 		}
+		lock.Release()
+		return nil, err
 	}
 	return freezer, nil
 }
@@ -128,8 +127,91 @@ func (f *freezer) Close() error {
 	return nil
 }
 
+// HasAncient returns an indicator whether the specified ancient data exists
+// in the freezer.
+func (f *freezer) HasAncient(kind string, number uint64) (bool, error) {
+	if table := f.tables[kind]; table != nil {
+		return table.has(number), nil
+	}
+	return false, nil
+}
+
+// Ancient retrieves an ancient binary blob from the append-only immutable files.
+func (f *freezer) Ancient(kind string, number uint64) ([]byte, error) {
+	if table := f.tables[kind]; table != nil {
+		return table.Retrieve(number)
+	}
+	return nil, errUnknownTable
+}
+
+// Ancients returns the length of the frozen items.
+func (f *freezer) Ancients() (uint64, error) {
+	return atomic.LoadUint64(&f.frozen), nil
+}
+
+// AppendAncient injects all binary blobs belong to block at the end of the
+// append-only immutable table files.
+//
+// Notably, this function is lock free but kind of thread-safe. All out-of-order
+// injection will be rejected. But if two injections with same number happen at
+// the same time, we can get into the trouble.
+func (f *freezer) AppendAncient(number uint64, hash, header, body, receipts, td []byte) (err error) {
+	// Ensure the binary blobs we are appending is continuous with freezer.
+	if atomic.LoadUint64(&f.frozen) != number {
+		return errOutOrderInsertion
+	}
+	// Rollback all inserted data if any insertion below failed to ensure
+	// the tables won't out of sync.
+	defer func() {
+		if err != nil {
+			rerr := f.repair()
+			if rerr != nil {
+				log.Crit("Failed to repair freezer", "err", rerr)
+			}
+			log.Info("Append ancient failed", "number", number, "err", err)
+		}
+	}()
+	// Inject all the components into the relevant data tables
+	if err := f.tables[freezerHashTable].Append(f.frozen, hash[:]); err != nil {
+		log.Error("Failed to append ancient hash", "number", f.frozen, "hash", hash, "err", err)
+		return err
+	}
+	if err := f.tables[freezerHeaderTable].Append(f.frozen, header); err != nil {
+		log.Error("Failed to append ancient header", "number", f.frozen, "hash", hash, "err", err)
+		return err
+	}
+	if err := f.tables[freezerBodiesTable].Append(f.frozen, body); err != nil {
+		log.Error("Failed to append ancient body", "number", f.frozen, "hash", hash, "err", err)
+		return err
+	}
+	if err := f.tables[freezerReceiptTable].Append(f.frozen, receipts); err != nil {
+		log.Error("Failed to append ancient receipts", "number", f.frozen, "hash", hash, "err", err)
+		return err
+	}
+	if err := f.tables[freezerDifficultyTable].Append(f.frozen, td); err != nil {
+		log.Error("Failed to append ancient difficulty", "number", f.frozen, "hash", hash, "err", err)
+		return err
+	}
+	atomic.AddUint64(&f.frozen, 1) // Only modify atomically
+	return nil
+}
+
+// Truncate discards any recent data above the provided threshold number.
+func (f *freezer) TruncateAncients(items uint64) error {
+	if atomic.LoadUint64(&f.frozen) <= items {
+		return nil
+	}
+	for _, table := range f.tables {
+		if err := table.truncate(items); err != nil {
+			return err
+		}
+	}
+	atomic.StoreUint64(&f.frozen, items)
+	return nil
+}
+
 // sync flushes all data tables to disk.
-func (f *freezer) sync() error {
+func (f *freezer) Sync() error {
 	var errs []error
 	for _, table := range f.tables {
 		if err := table.Sync(); err != nil {
@@ -142,14 +224,6 @@ func (f *freezer) sync() error {
 	return nil
 }
 
-// Ancient retrieves an ancient binary blob from the append-only immutable files.
-func (f *freezer) Ancient(kind string, number uint64) ([]byte, error) {
-	if table := f.tables[kind]; table != nil {
-		return table.Retrieve(number)
-	}
-	return nil, errUnknownTable
-}
-
 // freeze is a background thread that periodically checks the blockchain for any
 // import progress and moves ancient data from the fast database into the freezer.
 //
@@ -159,25 +233,22 @@ func (f *freezer) freeze(db ethdb.KeyValueStore) {
 	nfdb := &nofreezedb{KeyValueStore: db}
 
 	for {
-		// Retrieve the freezing threshold. In theory we're interested only in full
-		// blocks post-sync, but that would keep the live database enormous during
-		// dast sync. By picking the fast block, we still get to deep freeze all the
-		// final immutable data without having to wait for sync to finish.
-		hash := ReadHeadFastBlockHash(nfdb)
+		// Retrieve the freezing threshold.
+		hash := ReadHeadBlockHash(nfdb)
 		if hash == (common.Hash{}) {
-			log.Debug("Current fast block hash unavailable") // new chain, empty database
+			log.Debug("Current full block hash unavailable") // new chain, empty database
 			time.Sleep(freezerRecheckInterval)
 			continue
 		}
 		number := ReadHeaderNumber(nfdb, hash)
 		switch {
 		case number == nil:
-			log.Error("Current fast block number unavailable", "hash", hash)
+			log.Error("Current full block number unavailable", "hash", hash)
 			time.Sleep(freezerRecheckInterval)
 			continue
 
 		case *number < freezerBlockGraduation:
-			log.Debug("Current fast block not old enough", "number", *number, "hash", hash, "delay", freezerBlockGraduation)
+			log.Debug("Current full block not old enough", "number", *number, "hash", hash, "delay", freezerBlockGraduation)
 			time.Sleep(freezerRecheckInterval)
 			continue
 
@@ -188,7 +259,7 @@ func (f *freezer) freeze(db ethdb.KeyValueStore) {
 		}
 		head := ReadHeader(nfdb, hash, *number)
 		if head == nil {
-			log.Error("Current fast block unavailable", "number", *number, "hash", hash)
+			log.Error("Current full block unavailable", "number", *number, "hash", hash)
 			time.Sleep(freezerRecheckInterval)
 			continue
 		}
@@ -229,48 +300,35 @@ func (f *freezer) freeze(db ethdb.KeyValueStore) {
 				log.Error("Total difficulty missing, can't freeze", "number", f.frozen, "hash", hash)
 				break
 			}
+			log.Trace("Deep froze ancient block", "number", f.frozen, "hash", hash)
 			// Inject all the components into the relevant data tables
-			if err := f.tables["hashes"].Append(f.frozen, hash[:]); err != nil {
-				log.Error("Failed to deep freeze hash", "number", f.frozen, "hash", hash, "err", err)
-				break
-			}
-			if err := f.tables["headers"].Append(f.frozen, header); err != nil {
-				log.Error("Failed to deep freeze header", "number", f.frozen, "hash", hash, "err", err)
+			if err := f.AppendAncient(f.frozen, hash[:], header, body, receipts, td); err != nil {
 				break
 			}
-			if err := f.tables["bodies"].Append(f.frozen, body); err != nil {
-				log.Error("Failed to deep freeze body", "number", f.frozen, "hash", hash, "err", err)
-				break
-			}
-			if err := f.tables["receipts"].Append(f.frozen, receipts); err != nil {
-				log.Error("Failed to deep freeze receipts", "number", f.frozen, "hash", hash, "err", err)
-				break
-			}
-			if err := f.tables["diffs"].Append(f.frozen, td); err != nil {
-				log.Error("Failed to deep freeze difficulty", "number", f.frozen, "hash", hash, "err", err)
-				break
-			}
-			log.Trace("Deep froze ancient block", "number", f.frozen, "hash", hash)
-			atomic.AddUint64(&f.frozen, 1) // Only modify atomically
 			ancients = append(ancients, hash)
 		}
 		// Batch of blocks have been frozen, flush them before wiping from leveldb
-		if err := f.sync(); err != nil {
+		if err := f.Sync(); err != nil {
 			log.Crit("Failed to flush frozen tables", "err", err)
 		}
 		// Wipe out all data from the active database
 		batch := db.NewBatch()
+		for i := 0; i < len(ancients); i++ {
+			DeleteBlockWithoutNumber(batch, ancients[i], first+uint64(i))
+			DeleteCanonicalHash(batch, first+uint64(i))
+		}
+		if err := batch.Write(); err != nil {
+			log.Crit("Failed to delete frozen canonical blocks", "err", err)
+		}
+		batch.Reset()
+		// Wipe out side chain also.
 		for number := first; number < f.frozen; number++ {
-			for _, hash := range readAllHashes(db, number) {
-				if hash == ancients[number-first] {
-					deleteBlockWithoutNumber(batch, hash, number)
-				} else {
-					DeleteBlock(batch, hash, number)
-				}
+			for _, hash := range ReadAllHashes(db, number) {
+				DeleteBlock(batch, hash, number)
 			}
 		}
 		if err := batch.Write(); err != nil {
-			log.Crit("Failed to delete frozen items", "err", err)
+			log.Crit("Failed to delete frozen side blocks", "err", err)
 		}
 		// Log something friendly for the user
 		context := []interface{}{
@@ -287,3 +345,21 @@ func (f *freezer) freeze(db ethdb.KeyValueStore) {
 		}
 	}
 }
+
+// repair truncates all data tables to the same length.
+func (f *freezer) repair() error {
+	min := uint64(math.MaxUint64)
+	for _, table := range f.tables {
+		items := atomic.LoadUint64(&table.items)
+		if min > items {
+			min = items
+		}
+	}
+	for _, table := range f.tables {
+		if err := table.truncate(min); err != nil {
+			return err
+		}
+	}
+	atomic.StoreUint64(&f.frozen, min)
+	return nil
+}
diff --git a/core/rawdb/freezer_table.go b/core/rawdb/freezer_table.go
index 313ac8b78..8e117301b 100644
--- a/core/rawdb/freezer_table.go
+++ b/core/rawdb/freezer_table.go
@@ -39,6 +39,9 @@ var (
 	// errOutOfBounds is returned if the item requested is not contained within the
 	// freezer table.
 	errOutOfBounds = errors.New("out of bounds")
+
+	// errNotSupported is returned if the database doesn't support the required operation.
+	errNotSupported = errors.New("this operation is not supported")
 )
 
 // indexEntry contains the number/id of the file that the data resides in, aswell as the
@@ -451,7 +454,6 @@ func (t *freezerTable) getBounds(item uint64) (uint32, uint32, uint32, error) {
 // Retrieve looks up the data offset of an item with the given number and retrieves
 // the raw binary blob from the data file.
 func (t *freezerTable) Retrieve(item uint64) ([]byte, error) {
-
 	// Ensure the table and the item is accessible
 	if t.index == nil || t.head == nil {
 		return nil, errClosed
@@ -483,6 +485,12 @@ func (t *freezerTable) Retrieve(item uint64) ([]byte, error) {
 	return snappy.Decode(nil, blob)
 }
 
+// has returns an indicator whether the specified number data
+// exists in the freezer table.
+func (t *freezerTable) has(number uint64) bool {
+	return atomic.LoadUint64(&t.items) > number
+}
+
 // Sync pushes any pending data from memory out to disk. This is an expensive
 // operation, so use it with care.
 func (t *freezerTable) Sync() error {
diff --git a/core/rawdb/schema.go b/core/rawdb/schema.go
index 62b60e2f3..ebca17252 100644
--- a/core/rawdb/schema.go
+++ b/core/rawdb/schema.go
@@ -63,6 +63,23 @@ var (
 	preimageHitCounter = metrics.NewRegisteredCounter("db/preimage/hits", nil)
 )
 
+const (
+	// freezerHeaderTable indicates the name of the freezer header table.
+	freezerHeaderTable = "headers"
+
+	// freezerHashTable indicates the name of the freezer canonical hash table.
+	freezerHashTable = "hashes"
+
+	// freezerBodiesTable indicates the name of the freezer block body table.
+	freezerBodiesTable = "bodies"
+
+	// freezerReceiptTable indicates the name of the freezer receipts table.
+	freezerReceiptTable = "receipts"
+
+	// freezerDifficultyTable indicates the name of the freezer total difficulty table.
+	freezerDifficultyTable = "diffs"
+)
+
 // LegacyTxLookupEntry is the legacy TxLookupEntry definition with some unnecessary
 // fields.
 type LegacyTxLookupEntry struct {
diff --git a/core/rawdb/table.go b/core/rawdb/table.go
index 0b5e08b20..124678959 100644
--- a/core/rawdb/table.go
+++ b/core/rawdb/table.go
@@ -50,12 +50,42 @@ func (t *table) Get(key []byte) ([]byte, error) {
 	return t.db.Get(append([]byte(t.prefix), key...))
 }
 
+// HasAncient is a noop passthrough that just forwards the request to the underlying
+// database.
+func (t *table) HasAncient(kind string, number uint64) (bool, error) {
+	return t.db.HasAncient(kind, number)
+}
+
 // Ancient is a noop passthrough that just forwards the request to the underlying
 // database.
 func (t *table) Ancient(kind string, number uint64) ([]byte, error) {
 	return t.db.Ancient(kind, number)
 }
 
+// Ancients is a noop passthrough that just forwards the request to the underlying
+// database.
+func (t *table) Ancients() (uint64, error) {
+	return t.db.Ancients()
+}
+
+// AppendAncient is a noop passthrough that just forwards the request to the underlying
+// database.
+func (t *table) AppendAncient(number uint64, hash, header, body, receipts, td []byte) error {
+	return t.db.AppendAncient(number, hash, header, body, receipts, td)
+}
+
+// TruncateAncients is a noop passthrough that just forwards the request to the underlying
+// database.
+func (t *table) TruncateAncients(items uint64) error {
+	return t.db.TruncateAncients(items)
+}
+
+// Sync is a noop passthrough that just forwards the request to the underlying
+// database.
+func (t *table) Sync() error {
+	return t.db.Sync()
+}
+
 // Put inserts the given value into the database at a prefixed version of the
 // provided key.
 func (t *table) Put(key []byte, value []byte) error {
@@ -163,6 +193,6 @@ func (b *tableBatch) Reset() {
 }
 
 // Replay replays the batch contents.
-func (b *tableBatch) Replay(w ethdb.Writer) error {
+func (b *tableBatch) Replay(w ethdb.KeyValueWriter) error {
 	return b.batch.Replay(w)
 }
diff --git a/core/state/database.go b/core/state/database.go
index 8798b7380..ecc2c134d 100644
--- a/core/state/database.go
+++ b/core/state/database.go
@@ -93,7 +93,7 @@ type Trie interface {
 	// If the trie does not contain a value for key, the returned proof contains all
 	// nodes of the longest existing prefix of the key (at least the root), ending
 	// with the node that proves the absence of the key.
-	Prove(key []byte, fromLevel uint, proofDb ethdb.Writer) error
+	Prove(key []byte, fromLevel uint, proofDb ethdb.KeyValueWriter) error
 }
 
 // NewDatabase creates a backing store for state. The returned database is safe for
diff --git a/core/state/sync.go b/core/state/sync.go
index e4a08d293..ef7930527 100644
--- a/core/state/sync.go
+++ b/core/state/sync.go
@@ -26,7 +26,7 @@ import (
 )
 
 // NewStateSync create a new state trie download scheduler.
-func NewStateSync(root common.Hash, database ethdb.Reader, bloom *trie.SyncBloom) *trie.Sync {
+func NewStateSync(root common.Hash, database ethdb.KeyValueReader, bloom *trie.SyncBloom) *trie.Sync {
 	var syncer *trie.Sync
 	callback := func(leaf []byte, parent common.Hash) error {
 		var obj Account