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rocksdb/db/memtablelist.h

134 lines
4.2 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.
//
#pragma once
#include <string>
#include <list>
#include <vector>
#include "rocksdb/db.h"
#include "rocksdb/options.h"
#include "rocksdb/iterator.h"
#include "db/dbformat.h"
#include "db/skiplist.h"
#include "memtable.h"
namespace rocksdb {
class InternalKeyComparator;
class Mutex;
// keeps a list of immutable memtables in a vector. the list is immutable
// if refcount is bigger than one. It is used as a state for Get() and
// Iterator code paths
class MemTableListVersion {
public:
explicit MemTableListVersion(MemTableListVersion* old = nullptr);
void Ref();
void Unref(std::vector<MemTable*>* to_delete = nullptr);
int size() const;
// Search all the memtables starting from the most recent one.
// Return the most recent value found, if any.
bool Get(const LookupKey& key, std::string* value, Status* s,
MergeContext& merge_context, const Options& options);
void AddIterators(const ReadOptions& options,
std::vector<Iterator*>* iterator_list);
private:
// REQUIRE: m is mutable memtable
void Add(MemTable* m);
// REQUIRE: m is mutable memtable
void Remove(MemTable* m);
friend class MemTableList;
std::list<MemTable*> memlist_;
int size_ = 0;
int refs_ = 0;
};
// This class stores references to all the immutable memtables.
// The memtables are flushed to L0 as soon as possible and in
// any order. If there are more than one immutable memtable, their
// flushes can occur concurrently. However, they are 'committed'
// to the manifest in FIFO order to maintain correctness and
// recoverability from a crash.
class MemTableList {
public:
// A list of memtables.
explicit MemTableList(int min_write_buffer_number_to_merge)
: min_write_buffer_number_to_merge_(min_write_buffer_number_to_merge),
current_(new MemTableListVersion()),
num_flush_not_started_(0),
commit_in_progress_(false),
flush_requested_(false) {
imm_flush_needed.Release_Store(nullptr);
current_->Ref();
}
~MemTableList() {}
MemTableListVersion* current() { return current_; }
// so that backgrund threads can detect non-nullptr pointer to
// determine whether this is anything more to start flushing.
port::AtomicPointer imm_flush_needed;
// Returns the total number of memtables in the list
int size() const;
// Returns true if there is at least one memtable on which flush has
// not yet started.
bool IsFlushPending();
// Returns the earliest memtables that needs to be flushed. The returned
// memtables are guaranteed to be in the ascending order of created time.
void PickMemtablesToFlush(std::vector<MemTable*>* mems);
// Commit a successful flush in the manifest file
Status InstallMemtableFlushResults(const std::vector<MemTable*>& m,
VersionSet* vset, Status flushStatus,
port::Mutex* mu, Logger* info_log,
uint64_t file_number,
std::set<uint64_t>& pending_outputs,
std::vector<MemTable*>* to_delete,
Directory* db_directory);
// New memtables are inserted at the front of the list.
// Takes ownership of the referenced held on *m by the caller of Add().
void Add(MemTable* m);
// Returns an estimate of the number of bytes of data in use.
size_t ApproximateMemoryUsage();
// Request a flush of all existing memtables to storage
void FlushRequested() { flush_requested_ = true; }
// Copying allowed
// MemTableList(const MemTableList&);
// void operator=(const MemTableList&);
private:
// DB mutex held
void InstallNewVersion();
int min_write_buffer_number_to_merge_;
MemTableListVersion* current_;
// the number of elements that still need flushing
int num_flush_not_started_;
// committing in progress
bool commit_in_progress_;
// Requested a flush of all memtables to storage
bool flush_requested_;
};
} // namespace rocksdb