mirror of
https://github.com/google/leveldb.git
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ccf0fcd5c2
- Implemented Get() directly instead of building on top of a full merging iterator stack. This speeds up the "readrandom" benchmark by up to 15-30%. - Fixed an opensource compilation problem. Added --db=<name> flag to control where the database is placed. - Automatically compact a file when we have done enough overlapping seeks to that file. - Fixed a performance bug where we would read from at least one file in a level even if none of the files overlapped the key being read. - Makefile fix for Mac OSX installations that have XCode 4 without XCode 3. - Unified the two occurrences of binary search in a file-list into one routine. - Found and fixed a bug where we would unnecessarily search the last file when looking for a key larger than all data in the level. - A fix to avoid the need for trivial move compactions and therefore gets rid of two out of five syncs in "fillseq". - Removed the MANIFEST file write when switching to a new memtable/log-file for a 10-20% improvement on fill speed on ext4. - Adding a SNAPPY setting in the Makefile for folks who have Snappy installed. Snappy compresses values and speeds up writes. git-svn-id: https://leveldb.googlecode.com/svn/trunk@32 62dab493-f737-651d-591e-8d6aee1b9529
92 lines
2.7 KiB
C++
92 lines
2.7 KiB
C++
// 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 "leveldb/db.h"
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#include "db/dbformat.h"
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#include "db/skiplist.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 Mutex;
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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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// 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.
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//
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable.
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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,
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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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bool Get(const LookupKey& key, std::string* value, Status* s);
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private:
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~MemTable(); // Private since only Unref() should be used to delete it
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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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friend class MemTableIterator;
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friend class MemTableBackwardIterator;
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typedef SkipList<const char*, KeyComparator> Table;
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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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// No copying allowed
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MemTable(const MemTable&);
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void operator=(const MemTable&);
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};
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}
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#endif // STORAGE_LEVELDB_DB_MEMTABLE_H_
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