rocksdb/db/memtablelist.h
Kosie van der Merwe 8cd86a7be5 Fixing and adding some comments
Summary:
`MemTableList::Add()` neglected to mention that it took ownership of the reference held by its caller.

The comment in `MemTable::Get()` was wrong in describing the format of the key.

Test Plan: None

Reviewers: dhruba, sheki, emayanke, vamsi

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D7755
2013-01-03 17:13:56 -08:00

98 lines
2.8 KiB
C++

// Copyright (c) 2012 Facebook.
#ifndef STORAGE_LEVELDB_DB_MEMTABLELIST_H_
#define STORAGE_LEVELDB_DB_MEMTABLELIST_H_
#include <string>
#include <list>
#include "leveldb/db.h"
#include "db/dbformat.h"
#include "db/skiplist.h"
#include "util/arena.h"
#include "memtable.h"
namespace leveldb {
class InternalKeyComparator;
class Mutex;
class MemTableListIterator;
//
// This class stores refeernces 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.
MemTableList() : size_(0), num_flush_not_started_(0),
commit_in_progress_(false) {
imm_flush_needed.Release_Store(NULL);
}
~MemTableList() {};
// so that backgrund threads can detect non-NULL pointer to
// determine whether this is anything more to start flushing.
port::AtomicPointer imm_flush_needed;
// Increase reference count on all underling memtables
void RefAll();
// Drop reference count on all underling memtables
void UnrefAll();
// Returns the total number of memtables in the list
int size();
// Returns true if there is at least one memtable on which flush has
// not yet started.
bool IsFlushPending();
// Returns the earliest memtable that needs to be flushed.
// Returns null, if no such memtable exist.
MemTable* PickMemtableToFlush();
// Commit a successful flush in the manifest file
Status InstallMemtableFlushResults(MemTable* m,
VersionSet* vset, Status flushStatus,
port::Mutex* mu, Logger* info_log,
uint64_t file_number,
std::set<uint64_t>& pending_outputs);
// 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();
// 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);
// Returns the list of underlying memtables.
void GetMemTables(std::vector<MemTable*>* list);
// Copying allowed
// MemTableList(const MemTableList&);
// void operator=(const MemTableList&);
private:
std::list<MemTable*> memlist_;
int size_;
// the number of elements that still need flushing
int num_flush_not_started_;
// committing in progress
bool commit_in_progress_;
};
} // namespace leveldb
#endif // STORAGE_LEVELDB_DB_MEMTABLELIST_H_