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rocksdb/db/column_family.h

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// 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 <atomic>
#include "rocksdb/options.h"
#include "rocksdb/env.h"
#include "db/memtable_list.h"
#include "db/write_batch_internal.h"
#include "db/table_cache.h"
namespace rocksdb {
class Version;
class VersionSet;
class MemTable;
class MemTableListVersion;
class CompactionPicker;
class Compaction;
class InternalKey;
class InternalStats;
class ColumnFamilyData;
class DBImpl;
class ColumnFamilyHandleImpl : public ColumnFamilyHandle {
public:
// create while holding the mutex
ColumnFamilyHandleImpl(ColumnFamilyData* cfd, DBImpl* db, port::Mutex* mutex);
// destroy without mutex
virtual ~ColumnFamilyHandleImpl();
virtual ColumnFamilyData* cfd() const { return cfd_; }
virtual uint32_t GetID() const override;
private:
ColumnFamilyData* cfd_;
DBImpl* db_;
port::Mutex* mutex_;
};
// does not ref-count cfd_
class ColumnFamilyHandleInternal : public ColumnFamilyHandleImpl {
public:
ColumnFamilyHandleInternal()
: ColumnFamilyHandleImpl(nullptr, nullptr, nullptr) {}
void SetCFD(ColumnFamilyData* cfd) { internal_cfd_ = cfd; }
virtual ColumnFamilyData* cfd() const override { return internal_cfd_; }
private:
ColumnFamilyData* internal_cfd_;
};
// 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
autovector<MemTable*> to_delete;
// should be called outside the mutex
SuperVersion() = default;
~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);
};
extern ColumnFamilyOptions SanitizeOptions(const InternalKeyComparator* icmp,
const InternalFilterPolicy* ipolicy,
const ColumnFamilyOptions& src);
class ColumnFamilySet;
// column family metadata. not thread-safe. should be protected by db_mutex
class ColumnFamilyData {
public:
~ColumnFamilyData();
uint32_t GetID() const { return id_; }
const std::string& GetName() { return name_; }
// DB mutex held for all these
void Ref() { ++refs_; }
// will just decrease reference count to 0, but will not delete it. returns
// true if the ref count was decreased to zero and needs to be cleaned up by
// the caller
bool Unref() {
assert(refs_ > 0);
return --refs_ == 0;
}
bool Dead() { return refs_ == 0; }
// SetDropped() and IsDropped() are thread-safe
void SetDropped() {
// can't drop default CF
assert(id_ != 0);
dropped_.store(true);
}
bool IsDropped() const { return dropped_.load(); }
int NumberLevels() const { return options_.num_levels; }
void SetLogNumber(uint64_t log_number) { log_number_ = log_number; }
uint64_t GetLogNumber() const { return log_number_; }
const ColumnFamilyOptions* options() const { return &options_; }
const Options* full_options() const { return &full_options_; }
InternalStats* internal_stats();
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();
TableCache* table_cache() const { return table_cache_.get(); }
// See documentation in compaction_picker.h
Compaction* PickCompaction();
Compaction* CompactRange(int input_level, int output_level,
const InternalKey* begin, const InternalKey* end,
InternalKey** compaction_end);
CompactionPicker* compaction_picker() const {
return compaction_picker_.get();
}
const Comparator* user_comparator() const {
return internal_comparator_.user_comparator();
}
const InternalKeyComparator& internal_comparator() const {
return internal_comparator_;
}
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(const std::string& dbname, uint32_t id,
const std::string& name, Version* dummy_versions,
Cache* table_cache, const ColumnFamilyOptions& options,
const DBOptions* db_options,
const EnvOptions& storage_options,
ColumnFamilySet* column_family_set);
ColumnFamilyData* next() { return next_; }
uint32_t id_;
const std::string name_;
Version* dummy_versions_; // Head of circular doubly-linked list of versions.
Version* current_; // == dummy_versions->prev_
int refs_; // outstanding references to ColumnFamilyData
std::atomic<bool> dropped_; // true if client dropped it
const InternalKeyComparator internal_comparator_;
const InternalFilterPolicy internal_filter_policy_;
ColumnFamilyOptions const options_;
Options const full_options_;
std::unique_ptr<TableCache> table_cache_;
std::unique_ptr<InternalStats> internal_stats_;
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
ColumnFamilyData* next_;
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_;
// An object that keeps all the compaction stats
// and picks the next compaction
std::unique_ptr<CompactionPicker> compaction_picker_;
ColumnFamilySet* column_family_set_;
};
// 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++() {
// dummy is never dead, so this will never be infinite
do {
current_ = current_->next();
} while (current_->Dead());
return *this;
}
bool operator!=(const iterator& other) {
return this->current_ != other.current_;
}
ColumnFamilyData* operator*() { return current_; }
private:
ColumnFamilyData* current_;
};
ColumnFamilySet(const std::string& dbname, const DBOptions* db_options,
const EnvOptions& storage_options, Cache* table_cache);
~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(ColumnFamilyData* cfd);
iterator begin() { return iterator(dummy_cfd_->next()); }
iterator end() { return iterator(dummy_cfd_); }
// ColumnFamilySet has interesting thread-safety requirements
// * CreateColumnFamily() or DropColumnFamily() -- need to protect by DB
// mutex. Inside, column_family_data_ and column_families_ will be protected
// by Lock() and Unlock()
// * Iterate -- hold DB mutex, but you can release it in the body of
// iteration. If you release DB mutex in body, reference the column
// family before the mutex and unreference after you unlock, since the column
// family might get dropped when you release the DB mutex.
// * GetDefault(), GetColumnFamily(), Exists(), GetID() -- either inside of DB
// mutex or call Lock()
// * GetNextColumnFamilyID() -- inside of DB mutex
void Lock();
void Unlock();
private:
// when mutating: 1. DB mutex locked first, 2. spinlock locked second
// when reading, either: 1. lock DB mutex, or 2. lock spinlock
// (if both, respect the ordering to avoid deadlock!)
std::unordered_map<std::string, uint32_t> column_families_;
std::unordered_map<uint32_t, ColumnFamilyData*> column_family_data_;
uint32_t max_column_family_;
ColumnFamilyData* dummy_cfd_;
const std::string db_name_;
const DBOptions* const db_options_;
const EnvOptions storage_options_;
Cache* table_cache_;
std::atomic_flag spin_lock_;
};
class ColumnFamilyMemTablesImpl : public ColumnFamilyMemTables {
public:
explicit ColumnFamilyMemTablesImpl(ColumnFamilySet* column_family_set)
: column_family_set_(column_family_set), current_(nullptr) {}
// sets current_ to ColumnFamilyData with column_family_id
// returns false if column family doesn't exist
bool Seek(uint32_t column_family_id) override;
// Returns log number of the selected column family
uint64_t GetLogNumber() const override;
// REQUIRES: Seek() called first
virtual MemTable* GetMemTable() const override;
// Returns options for selected column family
// REQUIRES: Seek() called first
virtual const Options* GetFullOptions() const override;
// Returns column family handle for the selected column family
virtual ColumnFamilyHandle* GetColumnFamilyHandle() override;
private:
ColumnFamilySet* column_family_set_;
ColumnFamilyData* current_;
ColumnFamilyHandleInternal handle_;
};
} // namespace rocksdb