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rocksdb/db/column_family.h

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7.2 KiB

// 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
11 years ago
#include <unordered_map>
#include <string>
#include <vector>
#include "rocksdb/options.h"
#include "db/memtablelist.h"
#include "db/write_batch_internal.h"
namespace rocksdb {
class Version;
class VersionSet;
class MemTable;
class MemTableListVersion;
// holds references to memtable, all immutable memtables and version
struct SuperVersion {
MemTable* mem;
MemTableListVersion* imm;
Version* current;
std::atomic<uint32_t> refs;
// We need to_delete because during Cleanup(), imm->Unref() returns
// all memtables that we need to free through this vector. We then
// delete all those memtables outside of mutex, during destruction
std::vector<MemTable*> to_delete;
// should be called outside the mutex
SuperVersion();
~SuperVersion();
SuperVersion* Ref();
// Returns true if this was the last reference and caller should
// call Clenaup() and delete the object
bool Unref();
// call these two methods with db mutex held
// Cleanup unrefs mem, imm and current. Also, it stores all memtables
// that needs to be deleted in to_delete vector. Unrefing those
// objects needs to be done in the mutex
void Cleanup();
void Init(MemTable* new_mem, MemTableListVersion* new_imm,
Version* new_current);
};
// column family metadata. not thread-safe. should be protected by db_mutex
class ColumnFamilyData {
public:
ColumnFamilyData(uint32_t id, const std::string& name,
Version* dummy_versions, const ColumnFamilyOptions& options);
~ColumnFamilyData();
uint32_t GetID() const { return id_; }
const std::string& GetName() { return name_; }
void SetLogNumber(uint64_t log_number) { log_number_ = log_number; }
uint64_t GetLogNumber() const { return log_number_; }
ColumnFamilyOptions* options() { return &options_; }
MemTableList* imm() { return &imm_; }
MemTable* mem() { return mem_; }
Version* current() { return current_; }
Version* dummy_versions() { return dummy_versions_; }
void SetMemtable(MemTable* new_mem) { mem_ = new_mem; }
void SetCurrent(Version* current);
void CreateNewMemtable();
SuperVersion* GetSuperVersion() const { return super_version_; }
uint64_t GetSuperVersionNumber() const {
return super_version_number_.load();
}
// will return a pointer to SuperVersion* if previous SuperVersion
// if its reference count is zero and needs deletion or nullptr if not
// As argument takes a pointer to allocated SuperVersion to enable
// the clients to allocate SuperVersion outside of mutex.
SuperVersion* InstallSuperVersion(SuperVersion* new_superversion);
// A Flag indicating whether write needs to slowdown because of there are
// too many number of level0 files.
bool NeedSlowdownForNumLevel0Files() const {
return need_slowdown_for_num_level0_files_;
}
private:
friend class ColumnFamilySet;
ColumnFamilyData* next() { return next_.load(); }
uint32_t id_;
const std::string name_;
Version* dummy_versions_; // Head of circular doubly-linked list of versions.
Version* current_; // == dummy_versions->prev_
ColumnFamilyOptions options_;
MemTable* mem_;
MemTableList imm_;
SuperVersion* super_version_;
// An ordinal representing the current SuperVersion. Updated by
// InstallSuperVersion(), i.e. incremented every time super_version_
// changes.
std::atomic<uint64_t> super_version_number_;
// pointers for a circular linked list. we use it to support iterations
// that can be concurrent with writes
std::atomic<ColumnFamilyData*> next_;
std::atomic<ColumnFamilyData*> prev_;
// This is the earliest log file number that contains data from this
// Column Family. All earlier log files must be ignored and not
// recovered from
uint64_t log_number_;
// A flag indicating whether we should delay writes because
// we have too many level 0 files
bool need_slowdown_for_num_level0_files_;
};
// Thread safe only for reading without a writer. All access should be
// locked when adding or dropping column family
class ColumnFamilySet {
public:
class iterator {
public:
explicit iterator(ColumnFamilyData* cfd)
: current_(cfd) {}
iterator& operator++() {
current_ = current_->next();
return *this;
}
bool operator!=(const iterator& other) {
return this->current_ != other.current_;
}
ColumnFamilyData* operator*() { return current_; }
private:
ColumnFamilyData* current_;
};
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(dummy_cfd_->next()); }
iterator end() { return iterator(dummy_cfd_); }
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_;
ColumnFamilyData* dummy_cfd_;
};
class ColumnFamilyMemTablesImpl : public ColumnFamilyMemTables {
public:
explicit ColumnFamilyMemTablesImpl(ColumnFamilySet* column_family_set)
: column_family_set_(column_family_set), log_number_(0) {}
// If column_family_data->log_number is bigger than log_number,
// the memtable will not be returned.
// If log_number == 0, the memtable will be always returned
void SetLogNumber(uint64_t log_number) { log_number_ = log_number; }
// Returns the column families memtable if log_number == 0 || log_number <=
// column_family_data->log_number.
// If column family doesn't exist, it asserts
virtual MemTable* GetMemTable(uint32_t column_family_id) override;
private:
ColumnFamilySet* column_family_set_;
uint64_t log_number_;
};
} // namespace rocksdb