1、historydb概述

historydb，用于存储所有块读写集中写集的内容。

• historydb.go，定义核心接口HistoryDBProvider和HistoryDB。
• histmgr_helper.go，historydb工具函数。
• historyleveldb目录，historydb基于leveldb的实现。
       historyleveldb.go，HistoryDBProvider和HistoryDB接口实现，即historyleveldb.HistoryDBProvider和historyleveldb.historyDB结构体及方法。
       historyleveldb_query_executer.go，定义LevelHistoryDBQueryExecutor和historyScanner结构体及方法。

2、核心接口定义

HistoryDBProvider接口定义：

type HistoryDBProvider interface {    GetDBHandle(id string) (HistoryDB, error) //获取HistoryDB    Close() //关闭所有HistoryDB}//代码在core/ledger/kvledger/history/historydb/historydb.go

HistoryDB接口定义：

type HistoryDB interface {    //构造 LevelHistoryDBQueryExecutor    NewHistoryQueryExecutor(blockStore blkstorage.BlockStore) (ledger.HistoryQueryExecutor, error)    //提交Block入historyDB    Commit(block *common.Block) error    //获取savePointKey，即version.Height    GetLastSavepoint() (*version.Height, error)    //是否应该恢复，比较lastAvailableBlock和Savepoint    ShouldRecover(lastAvailableBlock uint64) (bool, uint64, error)    //提交丢失的块    CommitLostBlock(block *common.Block) error}//代码在core/ledger/kvledger/history/historydb/historydb.go

补充ledger.HistoryQueryExecutor接口定义：执行历史记录查询。

type HistoryQueryExecutor interface {    GetHistoryForKey(namespace string, key string) (commonledger.ResultsIterator, error) //按key查历史记录}//代码在core/ledger/ledger_interface.go

3、historydb工具函数

//构造复合HistoryKey，ns 0x00 key 0x00 blocknum trannumfunc ConstructCompositeHistoryKey(ns string, key string, blocknum uint64, trannum uint64) []byte//构造部分复合HistoryKey，ns 0x00 key 0x00 0xfffunc ConstructPartialCompositeHistoryKey(ns string, key string, endkey bool) []byte //按分隔符separator，分割bytesToSplitfunc SplitCompositeHistoryKey(bytesToSplit []byte, separator []byte) ([]byte, []byte) //代码在core/ledger/kvledger/history/historydb/histmgr_helper.go

4、HistoryDB接口实现

HistoryDB接口实现，即historyleveldb.historyDB结构体及方法。historyDB结构体定义如下：

type historyDB struct {    db     *leveldbhelper.DBHandle //leveldb    dbName string //dbName}//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb.go

涉及方法如下：

//构造historyDBfunc newHistoryDB(db *leveldbhelper.DBHandle, dbName string) *historyDB//do nothingfunc (historyDB *historyDB) Open() error//do nothingfunc (historyDB *historyDB) Close()//提交Block入historyDB，将读写集中写集入库，并更新savePointKeyfunc (historyDB *historyDB) Commit(block *common.Block) error//构造 LevelHistoryDBQueryExecutorfunc (historyDB *historyDB) NewHistoryQueryExecutor(blockStore blkstorage.BlockStore) (ledger.HistoryQueryExecutor, error)获取savePointKey，即version.Heightfunc (historyDB *historyDB) GetLastSavepoint() (*version.Height, error)//是否应该恢复，比较lastAvailableBlock和Savepointfunc (historyDB *historyDB) ShouldRecover(lastAvailableBlock uint64) (bool, uint64, error)//提交丢失的块，即调用historyDB.Commit(block)func (historyDB *historyDB) CommitLostBlock(block *common.Block) error//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb.go

func (historyDB historyDB) Commit(block common.Block) error代码如下：

blockNo := block.Header.Number //区块编号var tranNo uint64 //交易编号，初始化值为0dbBatch := leveldbhelper.NewUpdateBatch() //leveldb批量更新//交易验证代码，type TxValidationFlags []uint8//交易筛选器txsFilter := util.TxValidationFlags(block.Metadata.Metadata[common.BlockMetadataIndex_TRANSACTIONS_FILTER])if len(txsFilter) == 0 {    txsFilter = util.NewTxValidationFlags(len(block.Data.Data))    block.Metadata.Metadata[common.BlockMetadataIndex_TRANSACTIONS_FILTER] = txsFilter}for _, envBytes := range block.Data.Data {    if txsFilter.IsInvalid(int(tranNo)) { //检查指定的交易是否有效        tranNo++        continue    }    //[]byte反序列化为Envelope    env, err := putils.GetEnvelopeFromBlock(envBytes)    payload, err := putils.GetPayload(env) //e.Payload反序列化为Payload    //[]byte反序列化为ChannelHeader    chdr, err := putils.UnmarshalChannelHeader(payload.Header.ChannelHeader)    if common.HeaderType(chdr.Type) == common.HeaderType_ENDORSER_TRANSACTION { //背书交易，type HeaderType int32        respPayload, err := putils.GetActionFromEnvelope(envBytes) //获取ChaincodeAction        txRWSet := &rwsetutil.TxRwSet{}        err = txRWSet.FromProtoBytes(respPayload.Results) //[]byte反序列化后构造NsRwSet，加入txRWSet.NsRwSets        for _, nsRWSet := range txRWSet.NsRwSets {            ns := nsRWSet.NameSpace            for _, kvWrite := range nsRWSet.KvRwSet.Writes {                writeKey := kvWrite.Key                //txRWSet中写集入库                compositeHistoryKey := historydb.ConstructCompositeHistoryKey(ns, writeKey, blockNo, tranNo)                dbBatch.Put(compositeHistoryKey, emptyValue)            }        }    } else {        logger.Debugf("Skipping transaction [%d] since it is not an endorsement transaction\n", tranNo)    }    tranNo++}height := version.NewHeight(blockNo, tranNo)dbBatch.Put(savePointKey, height.ToBytes())err := historyDB.db.WriteBatch(dbBatch, true)//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb.go

Tx（Transaction 交易）相关更详细内容，参考：Fabric 1.0源代码笔记 之 Tx（Transaction 交易）

5、HistoryDBProvider接口实现

HistoryDBProvider接口实现，即historyleveldb.HistoryDBProvider结构体和方法。

type HistoryDBProvider struct {    dbProvider *leveldbhelper.Provider}//构造HistoryDBProviderfunc NewHistoryDBProvider() *HistoryDBProvider//获取HistoryDBfunc (provider *HistoryDBProvider) GetDBHandle(dbName string) (historydb.HistoryDB, error)//关闭所有HistoryDB句柄，调取provider.dbProvider.Close()func (provider *HistoryDBProvider) Close()//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb.go

6、LevelHistoryDBQueryExecutor和historyScanner结构体及方法

LevelHistoryDBQueryExecutor结构体及方法：实现ledger.HistoryQueryExecutor接口。

type LevelHistoryDBQueryExecutor struct {    historyDB  *historyDB    blockStore blkstorage.BlockStore //用于传递给historyScanner}//按key查historyDB，调用q.historyDB.db.GetIterator(compositeStartKey, compositeEndKey)func (q *LevelHistoryDBQueryExecutor) GetHistoryForKey(namespace string, key string) (commonledger.ResultsIterator, error) //代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb_query_executer.go

historyScanner结构体及方法：实现ledger.ResultsIterator接口。

type historyScanner struct {    compositePartialKey []byte //ns 0x00 key 0x00    namespace           string    key                 string    dbItr               iterator.Iterator //leveldb迭代器    blockStore          blkstorage.BlockStore}//构造historyScannerfunc newHistoryScanner(compositePartialKey []byte, namespace string, key string, dbItr iterator.Iterator, blockStore blkstorage.BlockStore) *historyScanner//按迭代器中key取blockNum和tranNum，再按blockNum和tranNum从blockStore中取Envelope，然后从Envelope的txRWSet.NsRwSets中按key查找并构造queryresult.KeyModificationfunc (scanner *historyScanner) Next() (commonledger.QueryResult, error)func (scanner *historyScanner) Close() //scanner.dbItr.Release()从Envelope的txRWSet.NsRwSets中按key查找并构造queryresult.KeyModificationfunc getKeyModificationFromTran(tranEnvelope *common.Envelope, namespace string, key string) (commonledger.QueryResult, error)//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb_query_executer.go

补充queryresult.KeyModification：

type KeyModification struct {    TxId      string //交易ID，ChannelHeader.TxId    Value     []byte //读写集中Value，KVWrite.Value    Timestamp *google_protobuf.Timestamp //ChannelHeader.Timestamp    IsDelete  bool //KVWrite.IsDelete}//代码在protos/ledger/queryresult/kv_query_result.pb.go