Summary: One of our profilings shows that Version::Get() sometimes is slow when getting pointer of user comparators or other global objects. In this patch: (1) we keep pointers of immutable objects in Version to avoid accesses them though option objects or cfd objects (2) table_reader is directly cached in FileMetaData so that table cache don't have to go through handle first to fetch it (3) If level 0 has less than 3 files, skip the filtering logic based on SST tables' key range. Smallest and largest key are stored in separated memory locations, which has potential cache misses Test Plan: make all check Reviewers: haobo, ljin Reviewed By: haobo CC: igor, yhchiang, nkg-, leveldb Differential Revision: https://reviews.facebook.net/D17739
493 lines
18 KiB
C++
493 lines
18 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// 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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//
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// The representation of a DBImpl consists of a set of Versions. The
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// newest version is called "current". Older versions may be kept
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// around to provide a consistent view to live iterators.
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//
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// Each Version keeps track of a set of Table files per level. The
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// entire set of versions is maintained in a VersionSet.
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//
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// Version,VersionSet are thread-compatible, but require external
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// synchronization on all accesses.
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#pragma once
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#include <map>
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#include <memory>
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#include <set>
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#include <vector>
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#include <deque>
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#include <atomic>
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#include <limits>
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#include "db/dbformat.h"
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#include "db/version_edit.h"
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#include "port/port.h"
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#include "db/table_cache.h"
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#include "db/compaction.h"
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#include "db/compaction_picker.h"
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#include "db/column_family.h"
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#include "db/log_reader.h"
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namespace rocksdb {
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namespace log { class Writer; }
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class Compaction;
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class CompactionPicker;
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class Iterator;
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class LogBuffer;
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class LookupKey;
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class MemTable;
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class Version;
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class VersionSet;
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class MergeContext;
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class ColumnFamilyData;
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class ColumnFamilySet;
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class TableCache;
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// Return the smallest index i such that files[i]->largest >= key.
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// Return files.size() if there is no such file.
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// REQUIRES: "files" contains a sorted list of non-overlapping files.
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extern int FindFile(const InternalKeyComparator& icmp,
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const std::vector<FileMetaData*>& files,
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const Slice& key);
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// Returns true iff some file in "files" overlaps the user key range
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// [*smallest,*largest].
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// smallest==nullptr represents a key smaller than all keys in the DB.
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// largest==nullptr represents a key largest than all keys in the DB.
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// REQUIRES: If disjoint_sorted_files, files[] contains disjoint ranges
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// in sorted order.
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extern bool SomeFileOverlapsRange(
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const InternalKeyComparator& icmp,
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bool disjoint_sorted_files,
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const std::vector<FileMetaData*>& files,
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const Slice* smallest_user_key,
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const Slice* largest_user_key);
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class Version {
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public:
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// Append to *iters a sequence of iterators that will
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// yield the contents of this Version when merged together.
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// REQUIRES: This version has been saved (see VersionSet::SaveTo)
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void AddIterators(const ReadOptions&, const EnvOptions& soptions,
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std::vector<Iterator*>* iters);
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// Lookup the value for key. If found, store it in *val and
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// return OK. Else return a non-OK status. Fills *stats.
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// Uses *operands to store merge_operator operations to apply later
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// REQUIRES: lock is not held
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struct GetStats {
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FileMetaData* seek_file;
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int seek_file_level;
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};
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void Get(const ReadOptions&, const LookupKey& key, std::string* val,
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Status* status, MergeContext* merge_context, GetStats* stats,
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bool* value_found = nullptr);
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// Adds "stats" into the current state. Returns true if a new
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// compaction may need to be triggered, false otherwise.
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// REQUIRES: lock is held
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bool UpdateStats(const GetStats& stats);
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// Updates internal structures that keep track of compaction scores
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// We use compaction scores to figure out which compaction to do next
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// REQUIRES: If Version is not yet saved to current_, it can be called without
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// a lock. Once a version is saved to current_, call only with mutex held
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void ComputeCompactionScore(std::vector<uint64_t>& size_being_compacted);
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// Reference count management (so Versions do not disappear out from
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// under live iterators)
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void Ref();
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// Decrease reference count. Delete the object if no reference left
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// and return true. Otherwise, return false.
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bool Unref();
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// Returns true iff some level needs a compaction.
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bool NeedsCompaction() const;
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// Returns the maxmimum compaction score for levels 1 to max
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double MaxCompactionScore() const { return max_compaction_score_; }
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// See field declaration
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int MaxCompactionScoreLevel() const { return max_compaction_score_level_; }
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void GetOverlappingInputs(
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int level,
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const InternalKey* begin, // nullptr means before all keys
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const InternalKey* end, // nullptr means after all keys
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std::vector<FileMetaData*>* inputs,
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int hint_index = -1, // index of overlap file
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int* file_index = nullptr); // return index of overlap file
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void GetOverlappingInputsBinarySearch(
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int level,
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const Slice& begin, // nullptr means before all keys
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const Slice& end, // nullptr means after all keys
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std::vector<FileMetaData*>* inputs,
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int hint_index, // index of overlap file
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int* file_index); // return index of overlap file
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void ExtendOverlappingInputs(
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int level,
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const Slice& begin, // nullptr means before all keys
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const Slice& end, // nullptr means after all keys
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std::vector<FileMetaData*>* inputs,
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unsigned int index); // start extending from this index
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// Returns true iff some file in the specified level overlaps
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// some part of [*smallest_user_key,*largest_user_key].
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// smallest_user_key==NULL represents a key smaller than all keys in the DB.
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// largest_user_key==NULL represents a key largest than all keys in the DB.
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bool OverlapInLevel(int level,
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const Slice* smallest_user_key,
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const Slice* largest_user_key);
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// Returns true iff the first or last file in inputs contains
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// an overlapping user key to the file "just outside" of it (i.e.
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// just after the last file, or just before the first file)
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// REQUIRES: "*inputs" is a sorted list of non-overlapping files
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bool HasOverlappingUserKey(const std::vector<FileMetaData*>* inputs,
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int level);
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// Return the level at which we should place a new memtable compaction
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// result that covers the range [smallest_user_key,largest_user_key].
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int PickLevelForMemTableOutput(const Slice& smallest_user_key,
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const Slice& largest_user_key);
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int NumberLevels() const { return num_levels_; }
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// REQUIRES: lock is held
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int NumLevelFiles(int level) const { return files_[level].size(); }
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// Return the combined file size of all files at the specified level.
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int64_t NumLevelBytes(int level) const;
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// Return a human-readable short (single-line) summary of the number
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// of files per level. Uses *scratch as backing store.
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struct LevelSummaryStorage {
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char buffer[100];
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};
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struct FileSummaryStorage {
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char buffer[1000];
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};
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const char* LevelSummary(LevelSummaryStorage* scratch) const;
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// Return a human-readable short (single-line) summary of files
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// in a specified level. Uses *scratch as backing store.
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const char* LevelFileSummary(FileSummaryStorage* scratch, int level) const;
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// Return the maximum overlapping data (in bytes) at next level for any
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// file at a level >= 1.
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int64_t MaxNextLevelOverlappingBytes();
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// Add all files listed in the current version to *live.
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void AddLiveFiles(std::set<uint64_t>* live);
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// Return a human readable string that describes this version's contents.
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std::string DebugString(bool hex = false) const;
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// Returns the version nuber of this version
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uint64_t GetVersionNumber() const { return version_number_; }
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// REQUIRES: lock is held
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// On success, *props will be populated with all SSTables' table properties.
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// The keys of `props` are the sst file name, the values of `props` are the
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// tables' propertis, represented as shared_ptr.
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Status GetPropertiesOfAllTables(TablePropertiesCollection* props);
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// used to sort files by size
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struct Fsize {
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int index;
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FileMetaData* file;
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};
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private:
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friend class Compaction;
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friend class VersionSet;
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friend class DBImpl;
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friend class ColumnFamilyData;
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friend class CompactionPicker;
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friend class LevelCompactionPicker;
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friend class UniversalCompactionPicker;
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class LevelFileNumIterator;
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Iterator* NewConcatenatingIterator(const ReadOptions&,
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const EnvOptions& soptions,
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int level) const;
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bool PrefixMayMatch(const ReadOptions& options, const EnvOptions& soptions,
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const Slice& internal_prefix, Iterator* level_iter) const;
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// Sort all files for this version based on their file size and
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// record results in files_by_size_. The largest files are listed first.
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void UpdateFilesBySize();
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ColumnFamilyData* cfd_; // ColumnFamilyData to which this Version belongs
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const InternalKeyComparator* internal_comparator_;
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const Comparator* user_comparator_;
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TableCache* table_cache_;
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const MergeOperator* merge_operator_;
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Logger* info_log_;
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Statistics* db_statistics_;
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VersionSet* vset_; // VersionSet to which this Version belongs
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Version* next_; // Next version in linked list
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Version* prev_; // Previous version in linked list
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int refs_; // Number of live refs to this version
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int num_levels_; // Number of levels
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// List of files per level, files in each level are arranged
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// in increasing order of keys
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std::vector<FileMetaData*>* files_;
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// A list for the same set of files that are stored in files_,
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// but files in each level are now sorted based on file
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// size. The file with the largest size is at the front.
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// This vector stores the index of the file from files_.
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std::vector<std::vector<int>> files_by_size_;
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// An index into files_by_size_ that specifies the first
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// file that is not yet compacted
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std::vector<int> next_file_to_compact_by_size_;
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// Only the first few entries of files_by_size_ are sorted.
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// There is no need to sort all the files because it is likely
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// that on a running system, we need to look at only the first
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// few largest files because a new version is created every few
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// seconds/minutes (because of concurrent compactions).
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static const int number_of_files_to_sort_ = 50;
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// Next file to compact based on seek stats.
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FileMetaData* file_to_compact_;
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int file_to_compact_level_;
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// Level that should be compacted next and its compaction score.
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// Score < 1 means compaction is not strictly needed. These fields
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// are initialized by Finalize().
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// The most critical level to be compacted is listed first
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// These are used to pick the best compaction level
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std::vector<double> compaction_score_;
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std::vector<int> compaction_level_;
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double max_compaction_score_; // max score in l1 to ln-1
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int max_compaction_score_level_; // level on which max score occurs
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// A version number that uniquely represents this version. This is
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// used for debugging and logging purposes only.
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uint64_t version_number_;
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Version(ColumnFamilyData* cfd, VersionSet* vset, uint64_t version_number = 0);
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~Version();
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// re-initializes the index that is used to offset into files_by_size_
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// to find the next compaction candidate file.
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void ResetNextCompactionIndex(int level) {
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next_file_to_compact_by_size_[level] = 0;
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}
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// No copying allowed
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Version(const Version&);
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void operator=(const Version&);
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};
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class VersionSet {
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public:
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VersionSet(const std::string& dbname, const DBOptions* options,
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const EnvOptions& storage_options, Cache* table_cache);
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~VersionSet();
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// Apply *edit to the current version to form a new descriptor that
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// is both saved to persistent state and installed as the new
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// current version. Will release *mu while actually writing to the file.
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// column_family_options has to be set if edit is column family add
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// REQUIRES: *mu is held on entry.
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// REQUIRES: no other thread concurrently calls LogAndApply()
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Status LogAndApply(ColumnFamilyData* column_family_data, VersionEdit* edit,
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port::Mutex* mu, Directory* db_directory = nullptr,
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bool new_descriptor_log = false,
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const ColumnFamilyOptions* column_family_options =
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nullptr);
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// Recover the last saved descriptor from persistent storage.
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// If read_only == true, Recover() will not complain if some column families
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// are not opened
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Status Recover(const std::vector<ColumnFamilyDescriptor>& column_families,
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bool read_only = false);
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// Reads a manifest file and returns a list of column families in
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// column_families.
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static Status ListColumnFamilies(std::vector<std::string>* column_families,
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const std::string& dbname, Env* env);
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#ifndef ROCKSDB_LITE
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// Try to reduce the number of levels. This call is valid when
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// only one level from the new max level to the old
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// max level containing files.
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// The call is static, since number of levels is immutable during
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// the lifetime of a RocksDB instance. It reduces number of levels
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// in a DB by applying changes to manifest.
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// For example, a db currently has 7 levels [0-6], and a call to
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// to reduce to 5 [0-4] can only be executed when only one level
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// among [4-6] contains files.
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static Status ReduceNumberOfLevels(const std::string& dbname,
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const Options* options,
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const EnvOptions& storage_options,
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int new_levels);
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// printf contents (for debugging)
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Status DumpManifest(Options& options, std::string& manifestFileName,
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bool verbose, bool hex = false);
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#endif // ROCKSDB_LITE
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// Return the current manifest file number
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uint64_t ManifestFileNumber() const { return manifest_file_number_; }
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uint64_t PendingManifestFileNumber() const {
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return pending_manifest_file_number_;
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}
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// Allocate and return a new file number
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uint64_t NewFileNumber() { return next_file_number_++; }
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// Arrange to reuse "file_number" unless a newer file number has
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// already been allocated.
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// REQUIRES: "file_number" was returned by a call to NewFileNumber().
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void ReuseFileNumber(uint64_t file_number) {
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if (next_file_number_ == file_number + 1) {
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next_file_number_ = file_number;
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}
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}
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// Return the last sequence number.
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uint64_t LastSequence() const {
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return last_sequence_.load(std::memory_order_acquire);
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}
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// Set the last sequence number to s.
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void SetLastSequence(uint64_t s) {
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assert(s >= last_sequence_);
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last_sequence_.store(s, std::memory_order_release);
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}
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// Mark the specified file number as used.
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void MarkFileNumberUsed(uint64_t number);
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// Return the log file number for the log file that is currently
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// being compacted, or zero if there is no such log file.
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uint64_t PrevLogNumber() const { return prev_log_number_; }
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// Returns the minimum log number such that all
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// log numbers less than or equal to it can be deleted
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uint64_t MinLogNumber() const {
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uint64_t min_log_num = std::numeric_limits<uint64_t>::max();
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for (auto cfd : *column_family_set_) {
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if (min_log_num > cfd->GetLogNumber()) {
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min_log_num = cfd->GetLogNumber();
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}
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}
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return min_log_num;
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}
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// Create an iterator that reads over the compaction inputs for "*c".
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// The caller should delete the iterator when no longer needed.
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Iterator* MakeInputIterator(Compaction* c);
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// Add all files listed in any live version to *live.
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void AddLiveFiles(std::vector<uint64_t>* live_list);
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// Return the approximate offset in the database of the data for
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// "key" as of version "v".
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uint64_t ApproximateOffsetOf(Version* v, const InternalKey& key);
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// Return the size of the current manifest file
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uint64_t ManifestFileSize() const { return manifest_file_size_; }
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// verify that the files that we started with for a compaction
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// still exist in the current version and in the same original level.
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// This ensures that a concurrent compaction did not erroneously
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// pick the same files to compact.
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bool VerifyCompactionFileConsistency(Compaction* c);
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Status GetMetadataForFile(uint64_t number, int* filelevel,
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FileMetaData** metadata, ColumnFamilyData** cfd);
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void GetLiveFilesMetaData(
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std::vector<LiveFileMetaData> *metadata);
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void GetObsoleteFiles(std::vector<FileMetaData*>* files);
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ColumnFamilySet* GetColumnFamilySet() { return column_family_set_.get(); }
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private:
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class Builder;
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struct ManifestWriter;
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friend class Version;
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struct LogReporter : public log::Reader::Reporter {
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Status* status;
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virtual void Corruption(size_t bytes, const Status& s) {
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if (this->status->ok()) *this->status = s;
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}
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};
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// Save current contents to *log
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Status WriteSnapshot(log::Writer* log);
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void AppendVersion(ColumnFamilyData* column_family_data, Version* v);
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bool ManifestContains(uint64_t manifest_file_number,
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const std::string& record) const;
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ColumnFamilyData* CreateColumnFamily(const ColumnFamilyOptions& options,
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VersionEdit* edit);
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std::unique_ptr<ColumnFamilySet> column_family_set_;
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Env* const env_;
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const std::string dbname_;
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const DBOptions* const options_;
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uint64_t next_file_number_;
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uint64_t manifest_file_number_;
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uint64_t pending_manifest_file_number_;
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std::atomic<uint64_t> last_sequence_;
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uint64_t prev_log_number_; // 0 or backing store for memtable being compacted
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// Opened lazily
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unique_ptr<log::Writer> descriptor_log_;
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// generates a increasing version number for every new version
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uint64_t current_version_number_;
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// Queue of writers to the manifest file
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std::deque<ManifestWriter*> manifest_writers_;
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// Current size of manifest file
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uint64_t manifest_file_size_;
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std::vector<FileMetaData*> obsolete_files_;
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// storage options for all reads and writes except compactions
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const EnvOptions& storage_options_;
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// storage options used for compactions. This is a copy of
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// storage_options_ but with readaheads set to readahead_compactions_.
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const EnvOptions storage_options_compactions_;
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// No copying allowed
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VersionSet(const VersionSet&);
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void operator=(const VersionSet&);
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void LogAndApplyCFHelper(VersionEdit* edit);
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void LogAndApplyHelper(ColumnFamilyData* cfd, Builder* b, Version* v,
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VersionEdit* edit, port::Mutex* mu);
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};
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} // namespace rocksdb
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