tkrzw_dbm_poly.cc

/*************************************************************************************************
 * Polymorphic database manager adapter
 *
 * Copyright 2020 Google LLC
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
 * except in compliance with the License.  You may obtain a copy of the License at
 *     https://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software distributed under the
 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied.  See the License for the specific language governing permissions
 * and limitations under the License.
 *************************************************************************************************/

#include "tkrzw_dbm.h"
#include "tkrzw_dbm_baby.h"
#include "tkrzw_dbm_cache.h"
#include "tkrzw_dbm_hash.h"
#include "tkrzw_dbm_poly.h"
#include "tkrzw_dbm_skip.h"
#include "tkrzw_dbm_std.h"
#include "tkrzw_dbm_tiny.h"
#include "tkrzw_dbm_tree.h"
#include "tkrzw_file.h"
#include "tkrzw_file_mmap.h"
#include "tkrzw_file_pos.h"
#include "tkrzw_file_util.h"
#include "tkrzw_lib_common.h"
#include "tkrzw_str_util.h"
#include "tkrzw_sys_config.h"

namespace tkrzw {

std::string GuessClassNameFromPath(const std::string& path) {
  const std::string base = StrLowerCase(PathToBaseName(path));
  std::string ext = PathToExtension(base);
  const size_t sym_pos = ext.find("-");
  if (sym_pos != std::string::npos) {
    ext = ext.substr(0, sym_pos);
  }
  if (ext == "tkh" || ext == "hash") {
    return "hash";
  } else if (ext == "tkt" || ext == "tree") {
    return "tree";
  } else if (ext == "tks" || ext == "skip") {
    return "skip";
  } else if (ext == "tkmt" || ext == "tiny" || ext == "flat") {
    return "tiny";
  } else if (ext == "tkmb" || ext == "baby") {
    return "baby";
  } else if (ext == "tkmc" || ext == "cache") {
    return "cache";
  } else if (ext == "tksh" || ext == "stdhash") {
    return "stdhash";
  } else if (ext == "tkst" || ext == "stdtree") {
    return "stdtree";
  }
  return "";
}

KeyComparator GetKeyComparatorByName(const std::string& comp_name) {
  const std::string lower_name = StrLowerCase(comp_name);
  if (lower_name == "lexicalkeycomparator" || lower_name == "lexical") {
    return LexicalKeyComparator;
  }
  if (lower_name == "lexicalCasekeycomparator" || lower_name == "lexicalcase") {
    return LexicalCaseKeyComparator;
  }
  if (lower_name == "decimalkeycomparator" || lower_name == "decimal") {
    return DecimalKeyComparator;
  }
  if (lower_name == "hexadecimalkeycomparator" || lower_name == "hexadecimal") {
    return HexadecimalKeyComparator;
  }
  if (lower_name == "realnumberkeycomparator" || lower_name == "realnumber") {
    return RealNumberKeyComparator;
  }
  if (lower_name == "pairlexicalkeycomparator" || lower_name == "pairlexical") {
    return PairLexicalKeyComparator;
  }
  if (lower_name == "pairlexicalCasekeycomparator" || lower_name == "pairlexicalcase") {
    return PairLexicalCaseKeyComparator;
  }
  if (lower_name == "pairdecimalkeycomparator" || lower_name == "pairdecimal") {
    return PairDecimalKeyComparator;
  }
  if (lower_name == "pairhexadecimalkeycomparator" || lower_name == "pairhexadecimal") {
    return PairHexadecimalKeyComparator;
  }
  if (lower_name == "pairrealnumberkeycomparator" || lower_name == "pairrealnumber") {
    return PairRealNumberKeyComparator;
  }
  return nullptr;
}

SkipDBM::ReducerType GetReducerByName(const std::string& func_name) {
  const std::string lower_name = StrLowerCase(func_name);
  if (lower_name == "reduceremove" || func_name == "remove") {
    return SkipDBM::ReduceRemove;
  } else if (lower_name == "reducetoFfrst" || lower_name == "first") {
    return SkipDBM::ReduceToFirst;
  } else if (lower_name == "reducetosecond" || lower_name == "second") {
    return SkipDBM::ReduceToSecond;
  } else if (lower_name == "reducetolast" || lower_name == "last") {
    return SkipDBM::ReduceToLast;
  } else if (lower_name == "reduceconcat" || lower_name == "concat") {
    return SkipDBM::ReduceConcat;
  } else if (lower_name == "reduceconcatwithnull" || lower_name == "concatnull") {
    return SkipDBM::ReduceConcatWithNull;
  } else if (lower_name == "reduceconcatwithtab" || lower_name == "concattab") {
    return SkipDBM::ReduceConcatWithTab;
  } else if (lower_name == "reduceconcatwithline" || lower_name == "concatline") {
    return SkipDBM::ReduceConcatWithLine;
  } else if (lower_name == "reducetototal" || lower_name == "total") {
    return SkipDBM::ReduceToTotal;
  }
  return nullptr;
}

void SetHashTuningParams(std::map<std::string, std::string>* params,
                         HashDBM::TuningParameters* tuning_params) {
  const std::string update_mode = StrLowerCase(SearchMap(*params, "update_mode", ""));
  if (update_mode == "update_in_place" || update_mode == "in_place") {
    tuning_params->update_mode = HashDBM::UPDATE_IN_PLACE;
  }
  if (update_mode == "update_appending" || update_mode == "appending") {
    tuning_params->update_mode = HashDBM::UPDATE_APPENDING;
  }
  tuning_params->offset_width = StrToInt(SearchMap(*params, "offset_width", "-1"));
  tuning_params->align_pow = StrToInt(SearchMap(*params, "align_pow", "-1"));
  tuning_params->num_buckets = StrToInt(SearchMap(*params, "num_buckets", "-1"));
  tuning_params->fbp_capacity = StrToInt(SearchMap(*params, "fbp_capacity", "-1"));
  tuning_params->lock_mem_buckets = StrToBool(SearchMap(*params, "lock_mem_buckets", "false"));
  params->erase("update_mode");
  params->erase("offset_width");
  params->erase("align_pow");
  params->erase("num_buckets");
  params->erase("fbp_capacity");
  params->erase("lock_mem_buckets");
}

void SetTreeTuningParams(std::map<std::string, std::string>* params,
                         TreeDBM::TuningParameters* tuning_params) {
  SetHashTuningParams(params, tuning_params);
  tuning_params->max_page_size = StrToInt(SearchMap(*params, "max_page_size", "-1"));
  tuning_params->max_branches = StrToInt(SearchMap(*params, "max_branches", "-1"));
  tuning_params->max_cached_pages = StrToInt(SearchMap(*params, "max_cached_pages", "-1"));
  tuning_params->key_comparator = GetKeyComparatorByName(SearchMap(*params, "key_comparator", ""));
  params->erase("max_page_size");
  params->erase("max_branches");
  params->erase("max_cached_pages");
  params->erase("key_comparator");
}

void SetSkipTuningParams(std::map<std::string, std::string>* params,
                         SkipDBM::TuningParameters* tuning_params) {
  tuning_params->offset_width = StrToInt(SearchMap(*params, "offset_width", "-1"));
  tuning_params->step_unit = StrToInt(SearchMap(*params, "step_unit", "-1"));
  tuning_params->max_level = StrToInt(SearchMap(*params, "max_level", "-1"));
  tuning_params->sort_mem_size = StrToInt(SearchMap(*params, "sort_mem_size", "-1"));
  tuning_params->insert_in_order = StrToBool(SearchMap(*params, "insert_in_order", "false"));
  tuning_params->max_cached_records = StrToInt(SearchMap(*params, "max_cached_records", "-1"));
  params->erase("offset_width");
  params->erase("step_unit");
  params->erase("max_level");
  params->erase("sort_mem_size");
  params->erase("insert_in_order");
  params->erase("max_cached_records");
}

PolyDBM::PolyDBM() : dbm_(nullptr), open_(false) {}

Status PolyDBM::OpenAdvanced(
    const std::string& path, bool writable, int32_t options,
    const std::map<std::string, std::string>& params) {
  if (dbm_ != nullptr) {
    return Status(Status::PRECONDITION_ERROR, "opened database");
  }
  std::map<std::string, std::string> mod_params = params;
  std::string class_name = StrLowerCase(SearchMap(mod_params, "dbm", ""));
  if (class_name.empty()) {
    class_name = GuessClassNameFromPath(path);
  }
  if (class_name.empty() && path.empty()) {
    class_name = "tiny";
  }
  mod_params.erase("dbm");
  if (class_name == "hash" || class_name == "hashdbm") {
    HashDBM::TuningParameters tuning_params;
    SetHashTuningParams(&mod_params, &tuning_params);
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    auto hash_dbm = std::make_unique<HashDBM>();
    const Status status = hash_dbm->OpenAdvanced(path, writable, options, tuning_params);
    if (status != Status::SUCCESS) {
      return status;
    }
    open_ = true;
    dbm_ = std::move(hash_dbm);
  } else if (class_name == "tree" || class_name == "treedbm") {
    TreeDBM::TuningParameters tuning_params;
    SetTreeTuningParams(&mod_params, &tuning_params);
    if (!SearchMap(mod_params, "key_comparator", "").empty() &&
        tuning_params.key_comparator == nullptr) {
      return Status(Status::INVALID_ARGUMENT_ERROR, "unsupported key comparator");
    }
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    auto tree_dbm = std::make_unique<TreeDBM>();
    const Status status = tree_dbm->OpenAdvanced(path, writable, options, tuning_params);
    if (status != Status::SUCCESS) {
      return status;
    }
    open_ = true;
    dbm_ = std::move(tree_dbm);
  } else if (class_name == "skip" || class_name == "skipdbm") {
    SkipDBM::TuningParameters tuning_params;
    SetSkipTuningParams(&mod_params, &tuning_params);
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    auto skip_dbm = std::make_unique<SkipDBM>();
    const Status status = skip_dbm->OpenAdvanced(path, writable, options, tuning_params);
    if (status != Status::SUCCESS) {
      return status;
    }
    open_ = true;
    dbm_ = std::move(skip_dbm);
  } else if (class_name == "tiny" || class_name == "tinydbm") {
    const int64_t num_buckets = StrToInt(SearchMap(mod_params, "num_buckets", "-1"));
    mod_params.erase("num_buckets");
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    auto tiny_dbm = std::make_unique<TinyDBM>(num_buckets);
    if (!path.empty()) {
      const Status status = tiny_dbm->Open(path, writable, options);
      if (status != Status::SUCCESS) {
        return status;
      }
      open_ = true;
    }
    dbm_ = std::move(tiny_dbm);
  } else if (class_name == "baby" || class_name == "babydbm") {
    KeyComparator key_comparator = LexicalKeyComparator;
    const std::string comp_name = SearchMap(mod_params, "key_comparator", "");
    if (!comp_name.empty()) {
      key_comparator = GetKeyComparatorByName(comp_name);
      if (key_comparator == nullptr) {
        return Status(Status::INVALID_ARGUMENT_ERROR,
                      StrCat("unsupported key comparator: ", comp_name));
      }
    }
    mod_params.erase("key_comparator");
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    auto baby_dbm = std::make_unique<BabyDBM>(key_comparator);
    if (!path.empty()) {
      const Status status = baby_dbm->Open(path, writable, options);
      if (status != Status::SUCCESS) {
        return status;
      }
      open_ = true;
    }
    dbm_ = std::move(baby_dbm);
  } else if (class_name == "cache" || class_name == "cachedbm") {
    const int64_t cap_rec_num = StrToInt(SearchMap(mod_params, "cap_rec_num", "-1"));
    const int64_t cap_mem_size = StrToInt(SearchMap(mod_params, "cap_mem_size", "-1"));
    mod_params.erase("cap_rec_num");
    mod_params.erase("cap_mem_size");
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    auto cache_dbm = std::make_unique<CacheDBM>(cap_rec_num, cap_mem_size);
    if (!path.empty()) {
      const Status status = cache_dbm->Open(path, writable, options);
      if (status != Status::SUCCESS) {
        return status;
      }
      open_ = true;
    }
    dbm_ = std::move(cache_dbm);
  } else if (class_name == "stdhash" || class_name == "stdhashdbm") {
    const int64_t num_buckets = StrToInt(SearchMap(mod_params, "num_buckets", "-1"));
    mod_params.erase("num_buckets");
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    auto stdhash_dbm = std::make_unique<StdHashDBM>(num_buckets);
    if (!path.empty()) {
      const Status status = stdhash_dbm->Open(path, writable, options);
      if (status != Status::SUCCESS) {
        return status;
      }
      open_ = true;
    }
    dbm_ = std::move(stdhash_dbm);
  } else if (class_name == "stdtree" || class_name == "stdtreedbm") {
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    auto stdtree_dbm = std::make_unique<StdTreeDBM>();
    if (!path.empty()) {
      const Status status = stdtree_dbm->Open(path, writable, options);
      if (status != Status::SUCCESS) {
        return status;
      }
      open_ = true;
    }
    dbm_ = std::move(stdtree_dbm);
  } else {
    return Status(Status::INVALID_ARGUMENT_ERROR, "unknown class");
  }
  return Status(Status::SUCCESS);
}

Status PolyDBM::Close() {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  Status status(Status::SUCCESS);
  if (open_) {
    status |= dbm_->Close();
  }
  open_ = false;
  dbm_.reset(nullptr);
  return status;
}

Status PolyDBM::Process(std::string_view key, RecordProcessor* proc, bool writable) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->Process(key, proc, writable);
}

Status PolyDBM::Get(std::string_view key, std::string* value) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->Get(key, value);
}

Status PolyDBM::Set(std::string_view key, std::string_view value, bool overwrite) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->Set(key, value, overwrite);
}

Status PolyDBM::Remove(std::string_view key) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->Remove(key);
}

Status PolyDBM::Append(std::string_view key, std::string_view value, std::string_view delim) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->Append(key, value, delim);
}

Status PolyDBM::ProcessEach(RecordProcessor* proc, bool writable) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->ProcessEach(proc, writable);
}

Status PolyDBM::Count(int64_t* count) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->Count(count);
}

Status PolyDBM::GetFileSize(int64_t* size) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->GetFileSize(size);
}

Status PolyDBM::GetFilePath(std::string* path) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->GetFilePath(path);
}

Status PolyDBM::Clear() {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->Clear();
}

Status PolyDBM::RebuildAdvanced(const std::map<std::string, std::string>& params) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  std::map<std::string, std::string> mod_params = params;
  if (typeid(*dbm_) == typeid(HashDBM)) {
    HashDBM* hash_dbm = dynamic_cast<HashDBM*>(dbm_.get());
    HashDBM::TuningParameters tuning_params;
    SetHashTuningParams(&mod_params, &tuning_params);
    const bool skip_broken_records = StrToBool(SearchMap(params, "skip_broken_records", "false"));
    mod_params.erase("skip_broken_records");
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    return hash_dbm->RebuildAdvanced(tuning_params, skip_broken_records);
  }
  if (typeid(*dbm_) == typeid(TreeDBM)) {
    TreeDBM* tree_dbm = dynamic_cast<TreeDBM*>(dbm_.get());
    TreeDBM::TuningParameters tuning_params;
    SetTreeTuningParams(&mod_params, &tuning_params);
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    return tree_dbm->RebuildAdvanced(tuning_params);
  }
  if (typeid(*dbm_) == typeid(SkipDBM)) {
    SkipDBM* skip_dbm = dynamic_cast<SkipDBM*>(dbm_.get());
    SkipDBM::TuningParameters tuning_params;
    SetSkipTuningParams(&mod_params, &tuning_params);
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    return skip_dbm->RebuildAdvanced(tuning_params);
  }
  if (typeid(*dbm_) == typeid(TinyDBM)) {
    TinyDBM* tiny_dbm = dynamic_cast<TinyDBM*>(dbm_.get());
    const int64_t num_buckets = StrToInt(SearchMap(mod_params, "num_buckets", "-1"));
    mod_params.erase("num_buckets");
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    return tiny_dbm->RebuildAdvanced(num_buckets);
  }
  if (typeid(*dbm_) == typeid(CacheDBM)) {
    CacheDBM* cache_dbm = dynamic_cast<CacheDBM*>(dbm_.get());
    const int64_t cap_rec_num = StrToInt(SearchMap(mod_params, "cap_rec_num", "-1"));
    const int64_t cap_mem_size = StrToInt(SearchMap(mod_params, "cap_mem_size", "-1"));
    mod_params.erase("cap_rec_num");
    mod_params.erase("cap_mem_size");
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    return cache_dbm->RebuildAdvanced(cap_rec_num, cap_mem_size);
  }
  if (!mod_params.empty()) {
    return Status(Status::INVALID_ARGUMENT_ERROR,
                  StrCat("unsupported parameter: ", mod_params.begin()->first));
  }
  return dbm_->Rebuild();
}

Status PolyDBM::ShouldBeRebuilt(bool* tobe) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  return dbm_->ShouldBeRebuilt(tobe);
}

Status PolyDBM::SynchronizeAdvanced(
    bool hard, FileProcessor* proc, const std::map<std::string, std::string>& params) {
  if (dbm_ == nullptr) {
    return Status(Status::PRECONDITION_ERROR, "not opened database");
  }
  std::map<std::string, std::string> mod_params = params;
  if (typeid(*dbm_) == typeid(SkipDBM)) {
    SkipDBM* skip_dbm = dynamic_cast<SkipDBM*>(dbm_.get());
    const auto& merge_paths = StrSplit(SearchMap(mod_params, "merge", ""), ":", true);
    for (const auto& merge_path : merge_paths) {
      const Status status = skip_dbm->MergeSkipDatabase(merge_path);
      if (status != Status::SUCCESS) {
        return status;
      }
    }
    const std::string reducer_name = SearchMap(mod_params, "reducer", "");
    SkipDBM::ReducerType reducer = nullptr;
    if (!reducer_name.empty()) {
      reducer = GetReducerByName(reducer_name);
      if (reducer == nullptr) {
        return Status(Status::INVALID_ARGUMENT_ERROR,
                      StrCat("unsupported reducer: ", reducer_name));
      }
    }
    mod_params.erase("merge");
    mod_params.erase("reducer");
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
    return skip_dbm->SynchronizeAdvanced(hard, proc, reducer);
  } else {
    if (!mod_params.empty()) {
      return Status(Status::INVALID_ARGUMENT_ERROR,
                    StrCat("unsupported parameter: ", mod_params.begin()->first));
    }
  }
  return dbm_->Synchronize(hard, proc);
}

std::vector<std::pair<std::string, std::string>> PolyDBM::Inspect() {
  if (dbm_ == nullptr) {
    return std::vector<std::pair<std::string, std::string>>();
  }
  return dbm_->Inspect();
}

bool PolyDBM::IsOpen() const {
  if (dbm_ == nullptr) {
    return false;
  }
  return dbm_->IsOpen();
}

bool PolyDBM::IsWritable() const {
  if (dbm_ == nullptr) {
    return false;
  }
  return dbm_->IsWritable();
}

bool PolyDBM::IsHealthy() const {
  if (dbm_ == nullptr) {
    return false;
  }
  return dbm_->IsHealthy();
}

bool PolyDBM::IsOrdered() const {
  if (dbm_ == nullptr) {
    return false;
  }
  return dbm_->IsOrdered();
}

std::unique_ptr<DBM::Iterator> PolyDBM::MakeIterator() {
  if (dbm_ == nullptr) {
    return std::unique_ptr<DBM::Iterator>(nullptr);
  }
  std::unique_ptr<PolyDBM::Iterator> iter(new PolyDBM::Iterator(dbm_->MakeIterator()));
  return iter;
}

std::unique_ptr<DBM> PolyDBM::MakeDBM() const {
  return std::make_unique<PolyDBM>();
}

DBM* PolyDBM::GetInternalDBM() const {
  return dbm_.get();
}

Status PolyDBM::RestoreDatabase(
    const std::string& old_file_path, const std::string& new_file_path,
    const std::string& class_name, int64_t end_offset) {
  std::string mod_class_name = StrLowerCase(class_name);
  if (mod_class_name.empty()) {
    mod_class_name = GuessClassNameFromPath(old_file_path);
  }
  if (mod_class_name == "hash" || mod_class_name == "hashdbm") {
    return HashDBM::RestoreDatabase(old_file_path, new_file_path, end_offset);
  } else if (mod_class_name == "tree" || mod_class_name == "treedbm") {
    return TreeDBM::RestoreDatabase(old_file_path, new_file_path, end_offset);
  } else if (mod_class_name == "skip" || mod_class_name == "skipdbm") {
    return SkipDBM::RestoreDatabase(old_file_path, new_file_path);
  }
  return Status(Status::INFEASIBLE_ERROR, "unknown database class");
}

}  // namespace tkrzw

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