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>
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#include <atomic>
#include <limits>
#include "db/dbformat.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"
namespace rocksdb {
namespace log { class Writer; }
class Compaction;
class CompactionPicker;
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 files[i]->largest >= key.
// Return files.size() if there is no such file.
// REQUIRES: "files" contains a sorted list of non-overlapping files.
extern int FindFile(const InternalKeyComparator& icmp,
const std::vector<FileMetaData*>& files,
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, files[] contains disjoint ranges
// in sorted order.
extern bool SomeFileOverlapsRange(
const InternalKeyComparator& icmp,
bool disjoint_sorted_files,
const std::vector<FileMetaData*>& files,
const Slice* smallest_user_key,
const Slice* largest_user_key);
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,
std::vector<Iterator*>* iters);
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. Fills *stats.
[RocksDB] [MergeOperator] The new Merge Interface! Uses merge sequences. Summary: Here are the major changes to the Merge Interface. It has been expanded to handle cases where the MergeOperator is not associative. It does so by stacking up merge operations while scanning through the key history (i.e.: during Get() or Compaction), until a valid Put/Delete/end-of-history is encountered; it then applies all of the merge operations in the correct sequence starting with the base/sentinel value. I have also introduced an "AssociativeMerge" function which allows the user to take advantage of associative merge operations (such as in the case of counters). The implementation will always attempt to merge the operations/operands themselves together when they are encountered, and will resort to the "stacking" method if and only if the "associative-merge" fails. This implementation is conjectured to allow MergeOperator to handle the general case, while still providing the user with the ability to take advantage of certain efficiencies in their own merge-operator / data-structure. NOTE: This is a preliminary diff. This must still go through a lot of review, revision, and testing. Feedback welcome! Test Plan: -This is a preliminary diff. I have only just begun testing/debugging it. -I will be testing this with the existing MergeOperator use-cases and unit-tests (counters, string-append, and redis-lists) -I will be "desk-checking" and walking through the code with the help gdb. -I will find a way of stress-testing the new interface / implementation using db_bench, db_test, merge_test, and/or db_stress. -I will ensure that my tests cover all cases: Get-Memtable, Get-Immutable-Memtable, Get-from-Disk, Iterator-Range-Scan, Flush-Memtable-to-L0, Compaction-L0-L1, Compaction-Ln-L(n+1), Put/Delete found, Put/Delete not-found, end-of-history, end-of-file, etc. -A lot of feedback from the reviewers. Reviewers: haobo, dhruba, zshao, emayanke Reviewed By: haobo CC: leveldb Differential Revision: https://reviews.facebook.net/D11499
2013-08-06 05:14:32 +02:00
// Uses *operands to store merge_operator operations to apply later
// REQUIRES: lock is not held
struct GetStats {
FileMetaData* seek_file;
int seek_file_level;
};
void Get(const ReadOptions&, const LookupKey& key, std::string* val,
Status* status, MergeContext* merge_context, GetStats* stats,
bool* value_found = nullptr);
// Adds "stats" into the current state. Returns true if a new
// compaction may need to be triggered, false otherwise.
// REQUIRES: lock is held
bool UpdateStats(const GetStats& stats);
// 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
void ComputeCompactionScore(std::vector<uint64_t>& size_being_compacted);
// Update scores, pre-calculated variables. It needs to be called before
// applying the version to the version set.
void PrepareApply(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();
// Returns true iff some level needs a compaction.
bool NeedsCompaction() const;
// Returns the maxmimum compaction score for levels 1 to max
double MaxCompactionScore() const { return max_compaction_score_; }
// See field declaration
int MaxCompactionScoreLevel() const { return max_compaction_score_level_; }
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);
[RocksDB] [MergeOperator] The new Merge Interface! Uses merge sequences. Summary: Here are the major changes to the Merge Interface. It has been expanded to handle cases where the MergeOperator is not associative. It does so by stacking up merge operations while scanning through the key history (i.e.: during Get() or Compaction), until a valid Put/Delete/end-of-history is encountered; it then applies all of the merge operations in the correct sequence starting with the base/sentinel value. I have also introduced an "AssociativeMerge" function which allows the user to take advantage of associative merge operations (such as in the case of counters). The implementation will always attempt to merge the operations/operands themselves together when they are encountered, and will resort to the "stacking" method if and only if the "associative-merge" fails. This implementation is conjectured to allow MergeOperator to handle the general case, while still providing the user with the ability to take advantage of certain efficiencies in their own merge-operator / data-structure. NOTE: This is a preliminary diff. This must still go through a lot of review, revision, and testing. Feedback welcome! Test Plan: -This is a preliminary diff. I have only just begun testing/debugging it. -I will be testing this with the existing MergeOperator use-cases and unit-tests (counters, string-append, and redis-lists) -I will be "desk-checking" and walking through the code with the help gdb. -I will find a way of stress-testing the new interface / implementation using db_bench, db_test, merge_test, and/or db_stress. -I will ensure that my tests cover all cases: Get-Memtable, Get-Immutable-Memtable, Get-from-Disk, Iterator-Range-Scan, Flush-Memtable-to-L0, Compaction-L0-L1, Compaction-Ln-L(n+1), Put/Delete found, Put/Delete not-found, end-of-history, end-of-file, etc. -A lot of feedback from the reviewers. Reviewers: haobo, dhruba, zshao, emayanke Reviewed By: haobo CC: leveldb Differential Revision: https://reviews.facebook.net/D11499
2013-08-06 05:14:32 +02:00
// 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 Slice& smallest_user_key,
const Slice& largest_user_key);
int NumberLevels() const { return num_levels_; }
// REQUIRES: lock is held
int NumLevelFiles(int level) const { return files_[level].size(); }
// Return the combined file size of all files at the specified level.
int64_t NumLevelBytes(int level) const;
// Return a human-readable short (single-line) summary of the number
// of files per level. Uses *scratch as backing store.
struct LevelSummaryStorage {
char buffer[100];
};
struct FileSummaryStorage {
char buffer[1000];
};
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();
// Add all files listed in the current version to *live.
void AddLiveFiles(std::set<uint64_t>* 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, *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);
// used to sort files by size
struct Fsize {
int index;
FileMetaData* file;
};
private:
friend class Compaction;
friend class VersionSet;
friend class DBImpl;
friend class ColumnFamilyData;
friend class CompactionPicker;
friend class LevelCompactionPicker;
friend class UniversalCompactionPicker;
friend class FIFOCompactionPicker;
friend class ForwardIterator;
class LevelFileNumIterator;
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class LevelFileIteratorState;
bool PrefixMayMatch(const ReadOptions& options, Iterator* level_iter,
const Slice& internal_prefix) const;
// Update num_non_empty_levels_.
void UpdateNumNonEmptyLevels();
// 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
const InternalKeyComparator* internal_comparator_;
const Comparator* user_comparator_;
TableCache* table_cache_;
const MergeOperator* merge_operator_;
Logger* info_log_;
Statistics* db_statistics_;
int num_levels_; // Number of levels
int num_non_empty_levels_; // Number of levels. Any level larger than it
// is guaranteed to be empty.
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
// 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 int number_of_files_to_sort_ = 50;
// Next file to compact based on seek stats.
FileMetaData* file_to_compact_;
int file_to_compact_level_;
// 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_; // max score in l1 to ln-1
int max_compaction_score_level_; // level on which max score occurs
// 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);
FileIndexer file_indexer_;
~Version();
// 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;
}
// No copying allowed
Version(const Version&);
void operator=(const Version&);
};
class VersionSet {
public:
VersionSet(const std::string& dbname, const DBOptions* options,
const EnvOptions& storage_options, Cache* table_cache);
~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, 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& storage_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 ManifestFileNumber() const { return manifest_file_number_; }
uint64_t PendingManifestFileNumber() const {
return pending_manifest_file_number_;
}
// Allocate and return a new file number
uint64_t NewFileNumber() { return next_file_number_++; }
// Arrange to reuse "file_number" unless a newer file number has
// already been allocated.
// REQUIRES: "file_number" was returned by a call to NewFileNumber().
void ReuseFileNumber(uint64_t file_number) {
if (next_file_number_ == file_number + 1) {
next_file_number_ = file_number;
}
}
// 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.
void MarkFileNumberUsed(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 PrevLogNumber() 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<uint64_t>* 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 ManifestFileSize() 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(); }
private:
class Builder;
struct ManifestWriter;
friend class Version;
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& options,
VersionEdit* edit);
std::unique_ptr<ColumnFamilySet> column_family_set_;
Env* const env_;
const std::string dbname_;
const DBOptions* const options_;
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_;
// storage options for all reads and writes except compactions
const EnvOptions& storage_options_;
// storage options used for compactions. This is a copy of
// storage_options_ but with readaheads set to readahead_compactions_.
const EnvOptions storage_options_compactions_;
// No copying allowed
VersionSet(const VersionSet&);
void operator=(const VersionSet&);
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void LogAndApplyCFHelper(VersionEdit* edit);
void LogAndApplyHelper(ColumnFamilyData* cfd, Builder* b, Version* v,
VersionEdit* edit, port::Mutex* mu);
};
} // namespace rocksdb