delete

8 月之前 · 2ab4c1aa47
--- a/db/NewDB.cc
+++ b/db/NewDB.cc
@ -1,663 +0,0 @@
 #include "db/NewDB.h"
 #include "util/coding.h"
 #include "db/write_batch_internal.h"
 #include "db/version_set.h"
 #include "db/db_impl.h"
 #include <string>
 #include <sstream>
 #include <unordered_map>
 #include <map>
 #include <iostream>
 #include <mutex>
 #include <thread>
 #include <ctime>
 #include <condition_variable>
 #include <unordered_set>

 namespace leveldb{
 NewDB::~NewDB() {

 }

 // row lock
 std::condition_variable cv;
 std::mutex m;
 bool ready = false;
 // row lock

 std::string NewDB::SerializeValue(const FieldArray& fields){
    std::string value_str;
    for(const auto& pair : fields){
        std::string field = pair.first + ":" + pair.second;
        uint32_t field_size = field.size();
        char buffer[4];
        EncodeFixed32(buffer, field_size);
        value_str.append(buffer, 4);
        value_str.append(field);
    }
    return value_str;

    //   std::string s;
    //   for(auto& field : fields){
    //     PutLengthPrefixedSlice(&s, Slice(field.first));
    //     PutLengthPrefixedSlice(&s, Slice(field.second));
    //   }
    //   return s;
 }

 FieldArray NewDB::ParseValue(const std::string& value_str){
    FieldArray fields;
    const char* data = value_str.data();
    size_t length = value_str.size();

    while (length >= 4) {
        uint32_t field_size = DecodeFixed32(data);
        if (length < 4 + field_size) {
        break;
        }

        std::string field(data + 4, field_size);
        size_t colon_pos = field.find(':');

        std::string field_name = field.substr(0, colon_pos);
        std::string field_value = field.substr(colon_pos + 1);

        fields.push_back(std::make_pair(field_name,field_value));

        data += 4 + field_size;
        length -= 4 + field_size;
    }

    return fields;

    //   Slice input(value_str);
    //   Slice v1,v2;
    //   FieldArray fields;
    //   while(v1!=Slice()){
    //     GetLengthPrefixedSlice(&input, &v1);
    //     GetLengthPrefixedSlice(&input, &v2);
    //     fields.push_back(std::make_pair(v1.ToString(), v2.ToString()));
    //   }
    //   return fields; 
 }

 // 构造索引的key，结构：FieldName_FieldValue_Key-橙
 std::string NewDB::ConstructIndexKey(const Slice& key, const Field& field){
    // std::string s;
    // PutLengthPrefixedSlice(&s, Slice(field.first));
    // PutLengthPrefixedSlice(&s, Slice(field.second));
    // PutLengthPrefixedSlice(&s, key);
    // return s;

    std::ostringstream oss;
    oss << field.first << ":" << field.second << "_" << key.ToString();  
    return oss.str(); 
 }

 // 从索引键中提取原数据的键
 std::string NewDB::ExtractIndexKey(const Slice& key){
    // Slice input(key.ToString());
    // Slice v;
    // GetLengthPrefixedSlice(&input, &v);
    // GetLengthPrefixedSlice(&input, &v);
    // GetLengthPrefixedSlice(&input, &v);
    // return v.ToString(); 

    //extract key of dataDB from key of indexDB
    std::string fullKey(key.data(), key.size());
    // size_t pos1 = fullKey.find('_');
    size_t pos1 = fullKey.find('_');   
    return fullKey.substr(pos1 + 1);  // 提取 'Key' 部分
 }

 std::string NewDB::ConstructRecoverKey(std::string UserOpID, std::string TinyOpID, std::string DBname){
    std::string s;
    PutLengthPrefixedSlice(&s, Slice(UserOpID));
    PutLengthPrefixedSlice(&s, Slice(TinyOpID));
    PutLengthPrefixedSlice(&s, Slice(DBname));
    return s;
 }

 std::string NewDB::ConstructRecoverValue(std::string TinyOp, std::string key, std::string value){
    std::string s;
    PutLengthPrefixedSlice(&s, Slice(TinyOp));
    PutLengthPrefixedSlice(&s, Slice(key));
    PutLengthPrefixedSlice(&s, Slice(value));
    return s;
 }

 std::string NewDB::ExtractRecoverKey(std::string s){
    Slice input(s);
    Slice v;
    GetLengthPrefixedSlice(&input, &v);
    GetLengthPrefixedSlice(&input, &v);
    GetLengthPrefixedSlice(&input, &v);
    return v.ToString();  
 }

 std::pair<std::string, std::string> NewDB::ExtractRecoverValue(std::string s, std::string* TinyOp){
    Slice input(s);
    Slice v;
    GetLengthPrefixedSlice(&input, &v);
    *TinyOp = v.ToString();
    GetLengthPrefixedSlice(&input, &v);
    std::string key = v.ToString();
    GetLengthPrefixedSlice(&input, &v);
    std::string value = v.ToString();
    return std::make_pair(key, value);
 }

 std::string NewDB::ConstructUserOpID(std::thread::id thread_id){
    auto now = std::chrono::system_clock::now();
    std::time_t now_t = std::chrono::system_clock::to_time_t(now);

    std::ostringstream oss;
    oss << thread_id;
    std::string UserOpID = std::to_string(now_t) + oss.str();
    return UserOpID;
 }


 Status NewDB::Open(const Options& options, const std::string& name, NewDB** dbptr) {
    // 打开底层的数据库
    DB* dataDB;
    Status s1 = DB::Open(options, name + "_data", &dataDB);
    if (!s1.ok()) {
        return s1;  // 如果打开失败，返回错误
    }

    DB* indexDB;
    Status s2 = DB::Open(options, name + "_index", &indexDB);
    if (!s2.ok()) {
        return s2;  // 如果打开失败，返回错误
    }

    DB* recoverDB;
    Status s3 = DB::Open(options, name + "_recover", &recoverDB);
    if (!s3.ok()) {
        return s3;  // 如果打开失败，返回错误
    }
    // 创建一个 NewDB 实例
    *dbptr = new NewDB();

    // 初始化 data_db_,index_db_和recover_db_
    (*dbptr)->data_db_ = std::unique_ptr<DB>(dataDB);  // 将打开的数据库指针传递给 data_db_
    (*dbptr)->index_db_ = std::unique_ptr<DB>(indexDB);  // 创建 IndexDB
    (*dbptr)->recover_db_ = std::unique_ptr<DB>(recoverDB);

    (*dbptr)->TinyOpID = 0;

    // recover dataDB&indexDB using recoverDB
    leveldb::Iterator* iter = recoverDB->NewIterator(leveldb::ReadOptions());
    Slice recover_key;
    for(iter->SeekToFirst(); iter->Valid(); iter->Next()){
        recover_key = iter->key();
        std::string DBname = (*dbptr)->ExtractRecoverKey(recover_key.ToString());
        std::string TinyOp;
        std::pair<std::string, std::string> k_v = (*dbptr)->ExtractRecoverValue(iter->value().ToString(), &TinyOp);
        if(DBname == "dataDB"){
            if(TinyOp == "PUT"){
                dataDB->Put(leveldb::WriteOptions(), k_v.first, k_v.second);
            }
            else{
                dataDB->Delete(leveldb::WriteOptions(), k_v.first);
            }
        }
        else{
            if(TinyOp == "PUT"){
                indexDB->Put(leveldb::WriteOptions(), k_v.first, k_v.second);
            }
            else{
                indexDB->Delete(leveldb::WriteOptions(), k_v.first);
            }           
        }
        recoverDB->Delete(leveldb::WriteOptions(), recover_key);
    }
    // std::cout << "recover " << i << " rows, end key is " << keystr << std::endl;
    delete iter;

    // 重新构造indexed_fields
    Iterator* it = (*dbptr)->index_db_->NewIterator(ReadOptions());
    for (it->SeekToFirst(); it->Valid(); it->Next()) {
        // 只关心以 "index_field" 为前缀的键
        if (it->key().starts_with("index_field_read:")) {
            std::string field = it->key().ToString().substr(16); // 获取字段名
            (*dbptr)->indexed_fields_read.insert(field);
        }
        if (it->key().starts_with("index_field_write:")) {
            std::string field = it->key().ToString().substr(17); // 获取字段名
            (*dbptr)->indexed_fields_write.insert(field);
        }  
    }
    delete it;

    return Status::OK();  // 返回成功
 }


 Status NewDB::Put_fields(const WriteOptions& options, const Slice& key, const FieldArray& fields){
    std::string UserOpID = ConstructUserOpID(std::this_thread::get_id());
    
    // row lock
    std::unique_lock<std::mutex> lock(db_mutex_, std::defer_lock);
    std::unique_lock<std::mutex> row_lock(m, std::defer_lock);
    ready = (putting_keys.find(key.ToString()) == putting_keys.end()); // no another thread putting the same key

    if (!ready) { 
        cv.wait(row_lock, []{return ready;});
    }

    lock.lock();
    putting_keys.insert(key.ToString());
    lock.unlock();
    // row lock

    FieldArray current_fields;
    Status s = Get_fields(leveldb::ReadOptions(), key, &current_fields);

    leveldb::WriteBatch data_batch;
    leveldb::WriteBatch index_batch;
    leveldb::WriteBatch recover_batch;

    // uint64_t TinyOpID = 0;

    if(!s.ok()){        
        for (const auto& field : fields) {
            // 如果字段名在 indexed_fields_ 中，才插入二级索引
            if (indexed_fields_write.find(field.first) != indexed_fields_write.end()) {
                // 构造索引的key，结构：FieldName_FieldValue_Key
                std::string index_key = ConstructIndexKey(key, field);
                index_batch.Put(index_key, Slice());
                // prepare recover_batch
                std::string Recover_key = ConstructRecoverKey(UserOpID, std::to_string(TinyOpID), "indexDB");
                std::string Recover_value = ConstructRecoverValue("PUT", index_key, "");
                recover_batch.Put(Recover_key, Recover_value);

                TinyOpID = TinyOpID + 1;
            }
        }
        std::string value = SerializeValue(fields);
        data_batch.Put(key.ToString(), value);

        // put dataDB's k-v into recover_batch
        std::string Recover_key = ConstructRecoverKey(UserOpID, std::to_string(TinyOpID), "dataDB");
        std::string Recover_value = ConstructRecoverValue("PUT", key.ToString(), value);
        recover_batch.Put(Recover_key, Recover_value);

        TinyOpID = TinyOpID + 1;
    }

    else{
        std::pair<FieldArray, FieldArray> fieldarray_pair = UpdateIndex(options, key, fields, current_fields);

        // put ops in indexdb
        for (const auto& field : fieldarray_pair.first) {
            if (indexed_fields_write.find(field.first) != indexed_fields_write.end()) {
                // put into index_batch
                std::string index_key = ConstructIndexKey(key, field);
                index_batch.Put(index_key, Slice());
                // put into recover_batch
                std::string Recover_key = ConstructRecoverKey(UserOpID, std::to_string(TinyOpID), "indexDB");
                std::string Recover_value = ConstructRecoverValue("PUT", index_key, "");
                recover_batch.Put(Recover_key, Recover_value);

                TinyOpID = TinyOpID + 1;
            }
        }

        // put ops in datadb
        std::string value = SerializeValue(fields);
        data_batch.Put(key.ToString(), value);

        // put dataDB's k-v into recover_batch
        std::string Recover_key = ConstructRecoverKey(UserOpID, std::to_string(TinyOpID), "dataDB");
        std::string Recover_value = ConstructRecoverValue("PUT", key.ToString(), value);
        recover_batch.Put(Recover_key, Recover_value);
        TinyOpID = TinyOpID + 1;

        // delete ops in indexdb
        for (const auto& field : fieldarray_pair.second) {
            if (indexed_fields_write.find(field.first) != indexed_fields_write.end()) {
                // delete in index_batch
                std::string index_key = ConstructIndexKey(key, field);
                index_batch.Delete(index_key);
                // delete in recover_batch
                std::string Recover_key = ConstructRecoverKey(UserOpID, std::to_string(TinyOpID), "indexDB");
                std::string Recover_value = ConstructRecoverValue("DELETE", index_key, "");
                recover_batch.Put(Recover_key, Recover_value);

                TinyOpID = TinyOpID + 1;
            }
        }
    }

    // write into RocoverDB
    leveldb::WriteOptions write_options;
    s = recover_db_->Write(write_options, &recover_batch);
    if(!s.ok()){
        return s;
    }

    // write into indexDB
    Status status = index_db_->Write(write_options, &index_batch); 
    if(!status.ok()){
        return status;
    }     

    // write into dataDB
    Status data_status = data_db_->Write(write_options, &data_batch);
    if (!data_status.ok()) {
        return data_status; // 主数据写入失败，直接返回
    }

    //delete TinyOps of this UserOp in RecoverDB
    leveldb::WriteBatch batch;
    std::string prefix;
    PutLengthPrefixedSlice(&prefix, Slice(UserOpID));
    leveldb::Iterator* iter = recover_db_->NewIterator(leveldb::ReadOptions());
    for(iter->Seek(prefix); iter->Valid() && iter->key().starts_with(prefix); iter->Next()){
        Slice Recover_key = iter->key();
        batch.Delete(Recover_key);
    }
    delete iter;
    recover_db_->Write(leveldb::WriteOptions(), &batch);

    // row lock
    lock.lock();
    putting_keys.erase(key.ToString());
    lock.unlock();

    ready = true;
    cv.notify_all();
    // row lock

    return Status::OK();
 }

 std::pair<FieldArray, FieldArray> NewDB::UpdateIndex(const WriteOptions& options, const Slice& key, const FieldArray& fields, const FieldArray& current_fields){
    // 构建current_fields的映射
    std::unordered_map<std::string, std::string> current_map;
    for (const auto& field : current_fields) {
        current_map[field.first] = field.second;
    }

    // 构建fields的映射
    std::unordered_map<std::string, std::string> fields_map;
    for (const auto& field : fields) {
        fields_map[field.first] = field.second;
    }

    // 删除的字段
    FieldArray deleted_fields;
    // 新增的字段
    FieldArray insert_fields;

    // fields中的字段
    for (const auto& field : fields) {
        // fields中存在但current_fields中不存在
        if (current_map.find(field.first) == current_map.end()) {
            insert_fields.push_back(field);
        } else if (current_map[field.first] != field.second) {
            // current_fields中存在但是值不同
            insert_fields.push_back(field);
            deleted_fields.push_back(std::make_pair(field.first, current_map[field.first]));
        }
    }

    // current_fields中的字段
    for (const auto& field : current_fields) {
        if (fields_map.find(field.first) == fields_map.end()) {
            deleted_fields.push_back(field);
        }
    }    

    return std::make_pair(insert_fields, deleted_fields);
 }

 Status NewDB::Get_fields(const ReadOptions& options, const Slice& key, FieldArray* fields){
    //get value(fields) with key
    // 从 DataDB 获取数据
    Status s = data_db_->Get_fields(options, key, fields);   
    if (!s.ok()) {
        return s;  // 如果获取失败，返回状态
    }   
    return Status::OK();
 }

 std::vector<std::string> NewDB::FindKeysByField(Field &field){  
    //get keys with field
    std::vector<std::string> matching_keys;
    leveldb::DB* db = data_db_.get();
    matching_keys = data_db_->FindKeysByField(db, field);
    return matching_keys;
 }

 bool NewDB::Delete(const WriteOptions& options, const Slice& key){  
    std::string UserOpID = ConstructUserOpID(std::this_thread::get_id());

    leveldb::WriteBatch data_batch;
    leveldb::WriteBatch index_batch;
    leveldb::WriteBatch recover_batch;
    // uint64_t TinyOpID = 0;

    FieldArray fields;
    Status s = data_db_->Get_fields(leveldb::ReadOptions(), key, &fields);

    if(s.ok()){        
        // delete in datadb
        data_batch.Delete(key.ToString());

        std::string Recover_key = ConstructRecoverKey(UserOpID, std::to_string(TinyOpID), "dataDB");
        std::string Recover_value = ConstructRecoverValue("DELETE", key.ToString(), "");
        recover_batch.Put(Recover_key, Recover_value);
        TinyOpID = TinyOpID + 1;

        // delete in indexdb
        for (const auto& field : fields) {
            // 如果字段名在 indexed_fields_ 中，才插入二级索引
            if (indexed_fields_write.find(field.first) != indexed_fields_write.end()) {
                // 构造索引的key，结构：FieldName_FieldValue_Key
                std::string index_key = ConstructIndexKey(key, field);
                index_batch.Delete(index_key);
                // prepare recover_batch
                std::string Recover_key = ConstructRecoverKey(UserOpID, std::to_string(TinyOpID), "indexDB");
                std::string Recover_value = ConstructRecoverValue("DELETE", index_key, "");
                recover_batch.Put(Recover_key, Recover_value);

                TinyOpID = TinyOpID + 1;
            }
        }

        // write recoverDB
        Status s = recover_db_->Write(leveldb::WriteOptions(), &recover_batch);
        if(!s.ok()){
            return false;
        }

        // write dataDB
        s = data_db_->Write(leveldb::WriteOptions(), &data_batch);
        if(!s.ok()){
            return false;
        }

        // write indexDB
        s = index_db_->Write(leveldb::WriteOptions(), &index_batch);
        if(!s.ok()){
            return false;
        }

        //delete TinyOps of this UserOp in RecoverDB
        leveldb::WriteBatch batch;
        std::string prefix;
        PutLengthPrefixedSlice(&prefix, Slice(UserOpID));
        leveldb::Iterator* iter = recover_db_->NewIterator(leveldb::ReadOptions());
        for(iter->Seek(prefix); iter->Valid() && iter->key().starts_with(prefix); iter->Next()){
            Slice Recover_key = iter->key();
            batch.Delete(Recover_key);
        }
        delete iter;
        recover_db_->Write(leveldb::WriteOptions(), &batch);
    }
    else{
        return false;
    }

    return true;
 }



 bool NewDB::CreateIndexOnField(const std::string& field_name) {
    // 将索引字段元数据持久化到indexDB
    index_db_->Put(WriteOptions(), "index_field_write:" + field_name, "1");
    std::unique_lock<std::mutex> lock(db_mutex_, std::defer_lock);
    lock.lock();
    indexed_fields_write.insert(field_name);
    lock.unlock();

    const size_t BATCH_SIZE_LIMIT = 1000;  // 每个批次限制1000条记录
    size_t batch_count = 0;

    // 遍历 data_db_ 中的所有键值对
    leveldb::ReadOptions read_options;
    leveldb::WriteBatch batch;
    std::unique_ptr<leveldb::Iterator> it(data_db_->NewIterator(read_options));

    for (it->SeekToFirst(); it->Valid(); it->Next()) {
        // 获取主数据库的键值对
        std::string key = it->key().ToString();
        std::string value = it->value().ToString();

        // 解析值，提取字段数组
        FieldArray fields = ParseValue(value);

        // 查找指定字段
        for (const auto& field : fields) {
            if (field.first == field_name) {
                // 构造索引键
                std::string index_key = ConstructIndexKey(key, field);

                // 插入到索引数据库
                batch.Put(index_key, Slice());

                batch_count++;
                // 如果达到批次大小限制，执行写入
                if (batch_count >= BATCH_SIZE_LIMIT) {
                    leveldb::Status status = index_db_->Write(leveldb::WriteOptions(), &batch);
                    if (!status.ok()) {
                        return false;
                    }
                    batch.Clear();  // 清空批次，准备下一个批次
                    batch_count = 0;
                }
            }
        }
    }

    // 如果迭代器出错
    if (!it->status().ok()) {
        // 从头开始创建，覆盖掉原本失效的东西
        return false;
    }
    // 批量写入
    leveldb::WriteOptions write_options;
    Status status = index_db_->Write(write_options, &batch);
    if (!status.ok()) {
        return false;
    }

    // 将索引字段元数据持久化到indexDB
    index_db_->Put(WriteOptions(), "index_field_read:" + field_name, "1");
    lock.lock();
    indexed_fields_read.insert(field_name);
    lock.unlock();
    return true;
 }

 std::vector<std::string> NewDB::QueryByIndex(Field &field){   
    std::vector<std::string> matching_keys;

    if(indexed_fields_read.find(field.first) != indexed_fields_read.end()){
        std::string prefix = ConstructIndexKey(Slice(), field);   //前缀-字段名+字段值
        leveldb::Iterator* iter = index_db_->NewIterator(leveldb::ReadOptions());
        for(iter->Seek(prefix); iter->Valid() && iter->key().starts_with(prefix); iter->Next()){
            Slice index_key = iter->key();
            std::string data_key = ExtractIndexKey(index_key);  //解析索引键中的key
            matching_keys.push_back(data_key);
        }
        delete iter;

        // check these matching_keys and remove keys not in datadb
        for (auto& key:matching_keys) {
            FieldArray fields;
            Status s = data_db_->Get_fields(leveldb::ReadOptions(), key, &fields);

            // if field not in this k-v?
            int tag = 0;
            if(s.ok()){
                for(auto& each_field : fields){
                    if(each_field.first == field.first){
                        if(each_field.second == field.second){
                            tag = 1;
                        }
                    }
                }
            }
            if(tag == 0){
                matching_keys.erase(std::remove(matching_keys.begin(),matching_keys.end(),key),matching_keys.end());           
            }
            // if(!s.ok()){
            //     matching_keys.erase(std::remove(matching_keys.begin(),matching_keys.end(),key),matching_keys.end());
            // }
        }
    }

    return matching_keys;
 }

 bool NewDB::DeleteIndex(const std::string& field_name){    
    // 将索引字段元数据持久化到indexDB
    index_db_->Delete(WriteOptions(), "index_field_read:" + field_name);
    index_db_->Delete(WriteOptions(), "index_field_write:" + field_name);
    std::unique_lock<std::mutex> lock(db_mutex_, std::defer_lock);
    lock.lock();
    indexed_fields_read.erase(field_name);
    indexed_fields_write.erase(field_name);
    lock.unlock();

    const size_t BATCH_SIZE_LIMIT = 1000;  // 每个批次限制1000条记录
    size_t batch_count = 0;

    leveldb::WriteBatch delete_batch;

    std::string prefix = field_name;
    leveldb::Iterator* iter = index_db_->NewIterator(leveldb::ReadOptions());
    for(iter->Seek(prefix); iter->Valid() && iter->key().starts_with(prefix); iter->Next()){
        Slice index_key = iter->key();
        delete_batch.Delete(index_key);
        batch_count++;
        if (batch_count >= BATCH_SIZE_LIMIT) {
            leveldb::Status status = index_db_->Write(leveldb::WriteOptions(), &delete_batch);
            if (!status.ok()) {
                return false;
            }
            delete_batch.Clear();  // 清空批次，准备下一个批次
            batch_count = 0;
        }
    }
    delete iter;

    Status s = index_db_->Write(leveldb::WriteOptions(), &delete_batch);
    if(!s.ok()){
        return false;
    }

    return true;
 }

 }





--- a/db/NewDB.h
+++ b/db/NewDB.h
@ -1,79 +0,0 @@
 #ifndef NEWDB_H
 #define NEWDB_H

 #include <memory>
 #include <unordered_set>
 #include <mutex>
 #include <thread>
 #include "leveldb/db.h"
 #include "db/log_writer.h"

 namespace leveldb{

 class LEVELDB_EXPORT NewDB {
  public:
  NewDB() = default;

  NewDB(const NewDB&) = delete;
  NewDB& operator=(const NewDB&) = delete;

  virtual ~NewDB();

  std::string SerializeValue(const FieldArray& fields);    
  FieldArray ParseValue(const std::string& value_str);    
  std::string ConstructIndexKey(const Slice& key, const Field& field);
  std::string ExtractIndexKey(const Slice& key);
  std::string ConstructRecoverKey(std::string UserOpID, std::string TinyOpID, std::string DBname);
  std::string ConstructRecoverValue(std::string TinyOp, std::string key, std::string value);
  std::string ExtractRecoverKey(std::string s);
  std::pair<std::string, std::string> ExtractRecoverValue(std::string s, std::string* TinyOp);
  std::string ConstructUserOpID(std::thread::id thread_id);

  static Status Open(const Options& options, const std::string& name,
                      NewDB** dbptr);  // 改为返回 NewDB* 类型-橙

  Status Put_fields(const WriteOptions& options, const Slice& key,
                     const FieldArray& fields);
                    
  std::pair<FieldArray, FieldArray> UpdateIndex(const WriteOptions& options, const Slice& key, 
                const FieldArray& fields, const FieldArray& current_fields);


  Status Get_fields(const ReadOptions& options, const Slice& key,   
                     FieldArray* fields);

  bool Delete(const WriteOptions& options, const Slice& key);

  std::vector<std::string> FindKeysByField(Field &field);

  // std::string ConstructKey(const Slice& key, const Field& field);

  // std::string ExtractKey(const Slice& key);

  bool CreateIndexOnField(const std::string& field_name);

  std::vector<std::string> QueryByIndex(Field &field);

  bool DeleteIndex(const std::string& field_name);
  
  // 用于存储已经为其创建索引的字段名称。只有当字段名在这个集合中时，才会在 indexDB 中插入对应的索引条目。
  std::unordered_set<std::string> indexed_fields_read;
  std::unordered_set<std::string> indexed_fields_write;

  std::unordered_set<std::string> putting_keys;

  private:
  std::unique_ptr<DB> data_db_;

  std::unique_ptr<DB> index_db_;

  std::unique_ptr<DB> recover_db_;

  std::mutex db_mutex_;  // 用于跨数据库操作的互斥锁

  uint64_t TinyOpID;
 };

 }

 #endif