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rocksdb/db/version_set.h

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// 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.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
// The representation of a DBImpl consists of a set of Versions. The
// newest version is called "current". Older versions may be kept
// around to provide a consistent view to live iterators.
//
// Each Version keeps track of a set of Table files per level. The
// entire set of versions is maintained in a VersionSet.
//
// Version,VersionSet are thread-compatible, but require external
// synchronization on all accesses.
#pragma once
#include <map>
#include <memory>
#include <set>
#include <vector>
#include <deque>
#include <atomic>
#include <limits>
#include "db/dbformat.h"
#include "db/version_builder.h"
#include "db/version_edit.h"
#include "port/port.h"
#include "db/table_cache.h"
#include "db/compaction.h"
#include "db/compaction_picker.h"
#include "db/column_family.h"
#include "db/log_reader.h"
#include "db/file_indexer.h"
#include "db/write_controller.h"
namespace rocksdb {
namespace log {
class Writer;
}
class Compaction;
class Iterator;
class LogBuffer;
class LookupKey;
class MemTable;
class Version;
class VersionSet;
class MergeContext;
class ColumnFamilyData;
class ColumnFamilySet;
class TableCache;
class MergeIteratorBuilder;
// Return the smallest index i such that file_level.files[i]->largest >= key.
// Return file_level.num_files if there is no such file.
// REQUIRES: "file_level.files" contains a sorted list of
// non-overlapping files.
extern int FindFile(const InternalKeyComparator& icmp,
const LevelFilesBrief& file_level,
const Slice& key);
// Returns true iff some file in "files" overlaps the user key range
// [*smallest,*largest].
// smallest==nullptr represents a key smaller than all keys in the DB.
// largest==nullptr represents a key largest than all keys in the DB.
// REQUIRES: If disjoint_sorted_files, file_level.files[]
// contains disjoint ranges in sorted order.
extern bool SomeFileOverlapsRange(
const InternalKeyComparator& icmp,
bool disjoint_sorted_files,
const LevelFilesBrief& file_level,
const Slice* smallest_user_key,
const Slice* largest_user_key);
// Generate LevelFilesBrief from vector<FdWithKeyRange*>
// Would copy smallest_key and largest_key data to sequential memory
// arena: Arena used to allocate the memory
extern void DoGenerateLevelFilesBrief(LevelFilesBrief* file_level,
const std::vector<FileMetaData*>& files,
Arena* arena);
class VersionStorageInfo {
public:
VersionStorageInfo(const InternalKeyComparator* internal_comparator,
const Comparator* user_comparator, int num_levels,
CompactionStyle compaction_style,
VersionStorageInfo* src_vstorage);
~VersionStorageInfo();
void Reserve(int level, size_t size) { files_[level].reserve(size); }
void AddFile(int level, FileMetaData* f);
void SetFinalized() { finalized_ = true; }
// Update num_non_empty_levels_.
void UpdateNumNonEmptyLevels();
void GenerateFileIndexer() {
file_indexer_.UpdateIndex(&arena_, num_non_empty_levels_, files_);
}
// Update the accumulated stats from a file-meta.
void UpdateAccumulatedStats(FileMetaData* file_meta);
void ComputeCompensatedSizes();
// Updates internal structures that keep track of compaction scores
// We use compaction scores to figure out which compaction to do next
// REQUIRES: If Version is not yet saved to current_, it can be called without
// a lock. Once a version is saved to current_, call only with mutex held
// TODO find a better way to pass compaction_options_fifo.
void ComputeCompactionScore(
const MutableCFOptions& mutable_cf_options,
const CompactionOptionsFIFO& compaction_options_fifo,
std::vector<uint64_t>& size_being_compacted);
// Generate level_files_brief_ from files_
void GenerateLevelFilesBrief();
// Sort all files for this version based on their file size and
// record results in files_by_size_. The largest files are listed first.
void UpdateFilesBySize();
int MaxInputLevel() const;
// Returns the maxmimum compaction score for levels 1 to max
double max_compaction_score() const { return max_compaction_score_; }
// See field declaration
int max_compaction_score_level() const { return max_compaction_score_level_; }
// Return level number that has idx'th highest score
int CompactionScoreLevel(int idx) const { return compaction_level_[idx]; }
// Return idx'th highest score
double CompactionScore(int idx) const { return compaction_score_[idx]; }
void GetOverlappingInputs(
int level, const InternalKey* begin, // nullptr means before all keys
const InternalKey* end, // nullptr means after all keys
std::vector<FileMetaData*>* inputs,
int hint_index = -1, // index of overlap file
int* file_index = nullptr); // return index of overlap file
void GetOverlappingInputsBinarySearch(
int level, const Slice& begin, // nullptr means before all keys
const Slice& end, // nullptr means after all keys
std::vector<FileMetaData*>* inputs,
int hint_index, // index of overlap file
int* file_index); // return index of overlap file
void ExtendOverlappingInputs(
int level, const Slice& begin, // nullptr means before all keys
const Slice& end, // nullptr means after all keys
std::vector<FileMetaData*>* inputs,
unsigned int index); // start extending from this index
// Returns true iff some file in the specified level overlaps
// some part of [*smallest_user_key,*largest_user_key].
// smallest_user_key==NULL represents a key smaller than all keys in the DB.
// largest_user_key==NULL represents a key largest than all keys in the DB.
bool OverlapInLevel(int level, const Slice* smallest_user_key,
const Slice* largest_user_key);
// Returns true iff the first or last file in inputs contains
// an overlapping user key to the file "just outside" of it (i.e.
// just after the last file, or just before the first file)
// REQUIRES: "*inputs" is a sorted list of non-overlapping files
bool HasOverlappingUserKey(const std::vector<FileMetaData*>* inputs,
int level);
// Return the level at which we should place a new memtable compaction
// result that covers the range [smallest_user_key,largest_user_key].
int PickLevelForMemTableOutput(const MutableCFOptions& mutable_cf_options,
const Slice& smallest_user_key,
const Slice& largest_user_key);
int num_levels() const { return num_levels_; }
// REQUIRES: This version has been saved (see VersionSet::SaveTo)
int num_non_empty_levels() const {
assert(finalized_);
return num_non_empty_levels_;
}
// REQUIRES: This version has been saved (see VersionSet::SaveTo)
int NumLevelFiles(int level) const {
assert(finalized_);
return static_cast<int>(files_[level].size());
}
// Return the combined file size of all files at the specified level.
uint64_t NumLevelBytes(int level) const;
// REQUIRES: This version has been saved (see VersionSet::SaveTo)
const std::vector<FileMetaData*>& LevelFiles(int level) const {
return files_[level];
}
const rocksdb::LevelFilesBrief& LevelFilesBrief(int level) const {
assert(level < static_cast<int>(level_files_brief_.size()));
return level_files_brief_[level];
}
// REQUIRES: This version has been saved (see VersionSet::SaveTo)
const std::vector<int>& FilesBySize(int level) const {
assert(finalized_);
return files_by_size_[level];
}
// REQUIRES: lock is held
// Set the index that is used to offset into files_by_size_ to find
// the next compaction candidate file.
void SetNextCompactionIndex(int level, int index) {
next_file_to_compact_by_size_[level] = index;
}
// REQUIRES: lock is held
int NextCompactionIndex(int level) const {
return next_file_to_compact_by_size_[level];
}
// REQUIRES: This version has been saved (see VersionSet::SaveTo)
const FileIndexer& file_indexer() const {
assert(finalized_);
return file_indexer_;
}
// Only the first few entries of files_by_size_ are sorted.
// There is no need to sort all the files because it is likely
// that on a running system, we need to look at only the first
// few largest files because a new version is created every few
// seconds/minutes (because of concurrent compactions).
static const size_t kNumberFilesToSort = 50;
// Return a human-readable short (single-line) summary of the number
// of files per level. Uses *scratch as backing store.
struct LevelSummaryStorage {
char buffer[1000];
};
struct FileSummaryStorage {
char buffer[3000];
};
const char* LevelSummary(LevelSummaryStorage* scratch) const;
// Return a human-readable short (single-line) summary of files
// in a specified level. Uses *scratch as backing store.
const char* LevelFileSummary(FileSummaryStorage* scratch, int level) const;
// Return the maximum overlapping data (in bytes) at next level for any
// file at a level >= 1.
int64_t MaxNextLevelOverlappingBytes();
// Return a human readable string that describes this version's contents.
std::string DebugString(bool hex = false) const;
uint64_t GetAverageValueSize() const {
if (accumulated_num_non_deletions_ == 0) {
return 0;
}
assert(accumulated_raw_key_size_ + accumulated_raw_value_size_ > 0);
assert(accumulated_file_size_ > 0);
return accumulated_raw_value_size_ / accumulated_num_non_deletions_ *
accumulated_file_size_ /
(accumulated_raw_key_size_ + accumulated_raw_value_size_);
}
uint64_t GetEstimatedActiveKeys() const;
// re-initializes the index that is used to offset into files_by_size_
// to find the next compaction candidate file.
void ResetNextCompactionIndex(int level) {
next_file_to_compact_by_size_[level] = 0;
}
const InternalKeyComparator* InternalComparator() {
return internal_comparator_;
}
private:
const InternalKeyComparator* internal_comparator_;
const Comparator* user_comparator_;
int num_levels_; // Number of levels
int num_non_empty_levels_; // Number of levels. Any level larger than it
// is guaranteed to be empty.
// A short brief metadata of files per level
autovector<rocksdb::LevelFilesBrief> level_files_brief_;
FileIndexer file_indexer_;
Arena arena_; // Used to allocate space for file_levels_
CompactionStyle compaction_style_;
// List of files per level, files in each level are arranged
// in increasing order of keys
std::vector<FileMetaData*>* files_;
// A list for the same set of files that are stored in files_,
// but files in each level are now sorted based on file
// size. The file with the largest size is at the front.
// This vector stores the index of the file from files_.
std::vector<std::vector<int>> files_by_size_;
// An index into files_by_size_ that specifies the first
// file that is not yet compacted
std::vector<int> next_file_to_compact_by_size_;
// Only the first few entries of files_by_size_ are sorted.
// There is no need to sort all the files because it is likely
// that on a running system, we need to look at only the first
// few largest files because a new version is created every few
// seconds/minutes (because of concurrent compactions).
static const size_t number_of_files_to_sort_ = 50;
// Level that should be compacted next and its compaction score.
// Score < 1 means compaction is not strictly needed. These fields
// are initialized by Finalize().
// The most critical level to be compacted is listed first
// These are used to pick the best compaction level
std::vector<double> compaction_score_;
std::vector<int> compaction_level_;
double max_compaction_score_ = 0.0; // max score in l1 to ln-1
int max_compaction_score_level_ = 0; // level on which max score occurs
// the following are the sampled temporary stats.
// the current accumulated size of sampled files.
uint64_t accumulated_file_size_;
// the current accumulated size of all raw keys based on the sampled files.
uint64_t accumulated_raw_key_size_;
// the current accumulated size of all raw keys based on the sampled files.
uint64_t accumulated_raw_value_size_;
// total number of non-deletion entries
uint64_t accumulated_num_non_deletions_;
// total number of deletion entries
uint64_t accumulated_num_deletions_;
// the number of samples
uint64_t num_samples_;
bool finalized_;
friend class Version;
friend class VersionSet;
// No copying allowed
VersionStorageInfo(const VersionStorageInfo&) = delete;
void operator=(const VersionStorageInfo&) = delete;
};
class Version {
public:
// Append to *iters a sequence of iterators that will
// yield the contents of this Version when merged together.
// REQUIRES: This version has been saved (see VersionSet::SaveTo)
void AddIterators(const ReadOptions&, const EnvOptions& soptions,
MergeIteratorBuilder* merger_iter_builder);
// Lookup the value for key. If found, store it in *val and
// return OK. Else return a non-OK status.
// Uses *operands to store merge_operator operations to apply later
// REQUIRES: lock is not held
void Get(const ReadOptions&, const LookupKey& key, std::string* val,
Status* status, MergeContext* merge_context,
bool* value_found = nullptr);
// Update scores, pre-calculated variables. It needs to be called before
// applying the version to the version set.
void PrepareApply(const MutableCFOptions& mutable_cf_options,
std::vector<uint64_t>& size_being_compacted);
// Reference count management (so Versions do not disappear out from
// under live iterators)
void Ref();
// Decrease reference count. Delete the object if no reference left
// and return true. Otherwise, return false.
bool Unref();
// Add all files listed in the current version to *live.
void AddLiveFiles(std::vector<FileDescriptor>* live);
// Return a human readable string that describes this version's contents.
std::string DebugString(bool hex = false) const;
// Returns the version nuber of this version
uint64_t GetVersionNumber() const { return version_number_; }
// REQUIRES: lock is held
// On success, "tp" will contains the table properties of the file
// specified in "file_meta". If the file name of "file_meta" is
// known ahread, passing it by a non-null "fname" can save a
// file-name conversion.
Status GetTableProperties(std::shared_ptr<const TableProperties>* tp,
const FileMetaData* file_meta,
const std::string* fname = nullptr);
// REQUIRES: lock is held
// On success, *props will be populated with all SSTables' table properties.
// The keys of `props` are the sst file name, the values of `props` are the
// tables' propertis, represented as shared_ptr.
Status GetPropertiesOfAllTables(TablePropertiesCollection* props);
uint64_t GetEstimatedActiveKeys() {
return storage_info_.GetEstimatedActiveKeys();
}
size_t GetMemoryUsageByTableReaders();
ColumnFamilyData* cfd() const { return cfd_; }
// Return the next Version in the linked list. Used for debug only
Version* TEST_Next() const {
return next_;
}
VersionStorageInfo* storage_info() { return &storage_info_; }
VersionSet* version_set() { return vset_; }
void GetColumnFamilyMetaData(ColumnFamilyMetaData* cf_meta);
private:
friend class VersionSet;
const InternalKeyComparator* internal_comparator() const {
return storage_info_.internal_comparator_;
}
const Comparator* user_comparator() const {
return storage_info_.user_comparator_;
}
bool PrefixMayMatch(const ReadOptions& read_options, Iterator* level_iter,
const Slice& internal_prefix) const;
// The helper function of UpdateAccumulatedStats, which may fill the missing
// fields of file_mata from its associated TableProperties.
// Returns true if it does initialize FileMetaData.
bool MaybeInitializeFileMetaData(FileMetaData* file_meta);
// Update the accumulated stats associated with the current version.
// This accumulated stats will be used in compaction.
void UpdateAccumulatedStats();
// Sort all files for this version based on their file size and
// record results in files_by_size_. The largest files are listed first.
void UpdateFilesBySize();
ColumnFamilyData* cfd_; // ColumnFamilyData to which this Version belongs
Logger* info_log_;
Statistics* db_statistics_;
TableCache* table_cache_;
const MergeOperator* merge_operator_;
VersionStorageInfo storage_info_;
VersionSet* vset_; // VersionSet to which this Version belongs
Version* next_; // Next version in linked list
Version* prev_; // Previous version in linked list
int refs_; // Number of live refs to this version
// A version number that uniquely represents this version. This is
// used for debugging and logging purposes only.
uint64_t version_number_;
Version(ColumnFamilyData* cfd, VersionSet* vset, uint64_t version_number = 0);
~Version();
// No copying allowed
Version(const Version&);
void operator=(const Version&);
};
class VersionSet {
public:
VersionSet(const std::string& dbname, const DBOptions* db_options,
const EnvOptions& env_options, Cache* table_cache,
WriteController* write_controller);
~VersionSet();
// Apply *edit to the current version to form a new descriptor that
// is both saved to persistent state and installed as the new
// current version. Will release *mu while actually writing to the file.
// column_family_options has to be set if edit is column family add
// REQUIRES: *mu is held on entry.
// REQUIRES: no other thread concurrently calls LogAndApply()
Status LogAndApply(
ColumnFamilyData* column_family_data,
const MutableCFOptions& mutable_cf_options, VersionEdit* edit,
port::Mutex* mu, Directory* db_directory = nullptr,
bool new_descriptor_log = false,
const ColumnFamilyOptions* column_family_options = nullptr);
// Recover the last saved descriptor from persistent storage.
// If read_only == true, Recover() will not complain if some column families
// are not opened
Status Recover(const std::vector<ColumnFamilyDescriptor>& column_families,
bool read_only = false);
// Reads a manifest file and returns a list of column families in
// column_families.
static Status ListColumnFamilies(std::vector<std::string>* column_families,
const std::string& dbname, Env* env);
#ifndef ROCKSDB_LITE
// Try to reduce the number of levels. This call is valid when
// only one level from the new max level to the old
// max level containing files.
// The call is static, since number of levels is immutable during
// the lifetime of a RocksDB instance. It reduces number of levels
// in a DB by applying changes to manifest.
// For example, a db currently has 7 levels [0-6], and a call to
// to reduce to 5 [0-4] can only be executed when only one level
// among [4-6] contains files.
static Status ReduceNumberOfLevels(const std::string& dbname,
const Options* options,
const EnvOptions& env_options,
int new_levels);
// printf contents (for debugging)
Status DumpManifest(Options& options, std::string& manifestFileName,
bool verbose, bool hex = false);
#endif // ROCKSDB_LITE
// Return the current manifest file number
uint64_t manifest_file_number() const { return manifest_file_number_; }
uint64_t pending_manifest_file_number() const {
return pending_manifest_file_number_;
}
uint64_t current_next_file_number() const { return next_file_number_.load(); }
// Allocate and return a new file number
uint64_t NewFileNumber() { return next_file_number_.fetch_add(1); }
// Return the last sequence number.
uint64_t LastSequence() const {
return last_sequence_.load(std::memory_order_acquire);
}
// Set the last sequence number to s.
void SetLastSequence(uint64_t s) {
assert(s >= last_sequence_);
last_sequence_.store(s, std::memory_order_release);
}
// Mark the specified file number as used.
// REQUIRED: this is only called during single-threaded recovery
void MarkFileNumberUsedDuringRecovery(uint64_t number);
// Return the log file number for the log file that is currently
// being compacted, or zero if there is no such log file.
uint64_t prev_log_number() const { return prev_log_number_; }
// Returns the minimum log number such that all
// log numbers less than or equal to it can be deleted
uint64_t MinLogNumber() const {
uint64_t min_log_num = std::numeric_limits<uint64_t>::max();
for (auto cfd : *column_family_set_) {
if (min_log_num > cfd->GetLogNumber()) {
min_log_num = cfd->GetLogNumber();
}
}
return min_log_num;
}
// Create an iterator that reads over the compaction inputs for "*c".
// The caller should delete the iterator when no longer needed.
Iterator* MakeInputIterator(Compaction* c);
// Add all files listed in any live version to *live.
void AddLiveFiles(std::vector<FileDescriptor>* live_list);
// Return the approximate offset in the database of the data for
// "key" as of version "v".
uint64_t ApproximateOffsetOf(Version* v, const InternalKey& key);
// Return the size of the current manifest file
uint64_t manifest_file_size() const { return manifest_file_size_; }
// verify that the files that we started with for a compaction
// still exist in the current version and in the same original level.
// This ensures that a concurrent compaction did not erroneously
// pick the same files to compact.
bool VerifyCompactionFileConsistency(Compaction* c);
Status GetMetadataForFile(uint64_t number, int* filelevel,
FileMetaData** metadata, ColumnFamilyData** cfd);
void GetLiveFilesMetaData(std::vector<LiveFileMetaData> *metadata);
void GetObsoleteFiles(std::vector<FileMetaData*>* files);
ColumnFamilySet* GetColumnFamilySet() { return column_family_set_.get(); }
const EnvOptions& env_options() { return env_options_; }
private:
struct ManifestWriter;
friend class Version;
friend class DBImpl;
struct LogReporter : public log::Reader::Reporter {
Status* status;
virtual void Corruption(size_t bytes, const Status& s) {
if (this->status->ok()) *this->status = s;
}
};
// Save current contents to *log
Status WriteSnapshot(log::Writer* log);
void AppendVersion(ColumnFamilyData* column_family_data, Version* v);
bool ManifestContains(uint64_t manifest_file_number,
const std::string& record) const;
ColumnFamilyData* CreateColumnFamily(const ColumnFamilyOptions& cf_options,
VersionEdit* edit);
std::unique_ptr<ColumnFamilySet> column_family_set_;
Env* const env_;
const std::string dbname_;
const DBOptions* const db_options_;
std::atomic<uint64_t> next_file_number_;
uint64_t manifest_file_number_;
uint64_t pending_manifest_file_number_;
std::atomic<uint64_t> last_sequence_;
uint64_t prev_log_number_; // 0 or backing store for memtable being compacted
// Opened lazily
unique_ptr<log::Writer> descriptor_log_;
// generates a increasing version number for every new version
uint64_t current_version_number_;
// Queue of writers to the manifest file
std::deque<ManifestWriter*> manifest_writers_;
// Current size of manifest file
uint64_t manifest_file_size_;
std::vector<FileMetaData*> obsolete_files_;
// env options for all reads and writes except compactions
const EnvOptions& env_options_;
// env options used for compactions. This is a copy of
// env_options_ but with readaheads set to readahead_compactions_.
const EnvOptions env_options_compactions_;
// No copying allowed
VersionSet(const VersionSet&);
void operator=(const VersionSet&);
void LogAndApplyCFHelper(VersionEdit* edit);
void LogAndApplyHelper(ColumnFamilyData* cfd, VersionBuilder* b, Version* v,
VersionEdit* edit, port::Mutex* mu);
};
} // namespace rocksdb