rocksdb/db/column_family.h

//  Copyright (c) 2013, Facebook, Inc.  All rights reserved.
//  This source code is licensed under the BSD-style license found in the
//  LICENSE file in the root directory of this source tree. An additional grant
//  of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#pragma once

#include "rocksdb/options.h"

#include <map>
#include <string>
#include <vector>

namespace rocksdb {

class Version;
class VersionSet;

// column family metadata
struct ColumnFamilyData {
  uint32_t id;
  std::string name;
  Version* dummy_versions; // Head of circular doubly-linked list of versions.
  Version* current;        // == dummy_versions->prev_
  ColumnFamilyOptions options;

  ColumnFamilyData(uint32_t id, const std::string& name,
                   Version* dummy_versions, const ColumnFamilyOptions& options);
  ~ColumnFamilyData();
};

class ColumnFamilySet {
 public:
   class iterator {
    public:
     explicit iterator(
         std::unordered_map<uint32_t, ColumnFamilyData*>::iterator itr)
         : itr_(itr) {}
     iterator& operator++() {
       ++itr_;
       return *this;
     }
     bool operator!=(const iterator& other) { return this->itr_ != other.itr_; }
     ColumnFamilyData* operator*() { return itr_->second; }
    private:
     std::unordered_map<uint32_t, ColumnFamilyData*>::iterator itr_;
   };

  ColumnFamilySet();
  ~ColumnFamilySet();

  ColumnFamilyData* GetDefault() const;
  // GetColumnFamily() calls return nullptr if column family is not found
  ColumnFamilyData* GetColumnFamily(uint32_t id) const;
  bool Exists(uint32_t id);
  bool Exists(const std::string& name);
  uint32_t GetID(const std::string& name);
  // this call will return the next available column family ID. it guarantees
  // that there is no column family with id greater than or equal to the
  // returned value in the current running instance. It does not, however,
  // guarantee that the returned ID is unique accross RocksDB restarts.
  // For example, if a client adds a column family 6 and then drops it,
  // after a restart, we might reuse column family 6 ID.
  uint32_t GetNextColumnFamilyID();

  ColumnFamilyData* CreateColumnFamily(const std::string& name, uint32_t id,
                                       Version* dummy_version,
                                       const ColumnFamilyOptions& options);
  void DropColumnFamily(uint32_t id);

  iterator begin() { return iterator(column_family_data_.begin()); }
  iterator end() { return iterator(column_family_data_.end()); }

 private:
  std::unordered_map<std::string, uint32_t> column_families_;
  std::unordered_map<uint32_t, ColumnFamilyData*> column_family_data_;
  // we need to keep them alive because we still can't control the lifetime of
  // all of column family data members (options for example)
  std::vector<ColumnFamilyData*> droppped_column_families_;
  uint32_t max_column_family_;
};

}  // namespace rocksdb