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88 linhas
2.7 KiB
88 linhas
2.7 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#ifndef STORAGE_LEVELDB_DB_MEMTABLE_H_
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#define STORAGE_LEVELDB_DB_MEMTABLE_H_
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#include <string>
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#include "db/dbformat.h"
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#include "db/skiplist.h"
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#include "leveldb/db.h"
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#include "util/arena.h"
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namespace leveldb {
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class InternalKeyComparator;
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class MemTableIterator;
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class MemTable {
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public:
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// MemTables are reference counted. The initial reference count
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// is zero and the caller must call Ref() at least once.
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explicit MemTable(const InternalKeyComparator& comparator);
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MemTable(const MemTable&) = delete;
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MemTable& operator=(const MemTable&) = delete;
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// Increase reference count.
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void Ref() { ++refs_; }
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// Drop reference count. Delete if no more references exist.
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void Unref() {
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--refs_;
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assert(refs_ >= 0);
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if (refs_ <= 0) {
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delete this;
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}
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}
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// Returns an estimate of the number of bytes of data in use by this
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// data structure. It is safe to call when MemTable is being modified.
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size_t ApproximateMemoryUsage();
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// Return an iterator that yields the contents of the memtable.
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//
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// The caller must ensure that the underlying MemTable remains live
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// while the returned iterator is live. The keys returned by this
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// iterator are internal keys encoded by AppendInternalKey in the
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// db/format.{h,cc} module.
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Iterator* NewIterator();
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// Add an entry into memtable that maps key to value at the
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// specified sequence number and with the specified type.
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// Typically value will be empty if type==kTypeDeletion.
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void Add(SequenceNumber seq, ValueType type, const Slice& key,
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const Slice& value);
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// If memtable contains a value for key, store it in *value and return true.
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// If memtable contains a deletion for key, store a NotFound() error
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// in *status and return true.
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// Else, return false.
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std::chrono::system_clock::time_point insert_time; // 保存上次插入的时间，燕改
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bool Get(const LookupKey& key, std::string* value, Status* s);
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private:
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friend class MemTableIterator;
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friend class MemTableBackwardIterator;
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struct KeyComparator {
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const InternalKeyComparator comparator;
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explicit KeyComparator(const InternalKeyComparator& c) : comparator(c) {}
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int operator()(const char* a, const char* b) const;
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};
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typedef SkipList<const char*, KeyComparator> Table;
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~MemTable(); // Private since only Unref() should be used to delete it
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KeyComparator comparator_;
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int refs_;
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Arena arena_;
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Table table_;
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};
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_DB_MEMTABLE_H_
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