rocksdb/table/get_context.h
Huisheng Liu 904a60ff63 return timestamp from get (#6409)
Summary:
Added new Get() methods that return timestamp. Dummy implementation is given so that classes derived from DB don't need to be touched to provide their implementation. MultiGet is not included.

ReadRandom perf test (10 minutes) on the same development machine ram drive with the same DB data shows no regression (within marge of error). The test is adapted from https://github.com/facebook/rocksdb/wiki/RocksDB-In-Memory-Workload-Performance-Benchmarks.
    base line (commit 72ee067b9):
        101.712 micros/op 314602 ops/sec;   36.0 MB/s (5658999 of 5658999 found)
    This PR:
        100.288 micros/op 319071 ops/sec;   36.5 MB/s (5674999 of 5674999 found)

./db_bench --db=r:\rocksdb.github --num_levels=6 --key_size=20 --prefix_size=20 --keys_per_prefix=0 --value_size=100 --cache_size=2147483648 --cache_numshardbits=6 --compression_type=none --compression_ratio=1 --min_level_to_compress=-1 --disable_seek_compaction=1 --hard_rate_limit=2 --write_buffer_size=134217728 --max_write_buffer_number=2 --level0_file_num_compaction_trigger=8 --target_file_size_base=134217728 --max_bytes_for_level_base=1073741824 --disable_wal=0 --wal_dir=r:\rocksdb.github\WAL_LOG --sync=0 --verify_checksum=1 --delete_obsolete_files_period_micros=314572800 --max_background_compactions=4 --max_background_flushes=0 --level0_slowdown_writes_trigger=16 --level0_stop_writes_trigger=24 --statistics=0 --stats_per_interval=0 --stats_interval=1048576 --histogram=0 --use_plain_table=1 --open_files=-1 --mmap_read=1 --mmap_write=0 --memtablerep=prefix_hash --bloom_bits=10 --bloom_locality=1 --duration=600 --benchmarks=readrandom --use_existing_db=1 --num=25000000 --threads=32
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6409

Differential Revision: D20200086

Pulled By: riversand963

fbshipit-source-id: 490edd74d924f62bd8ae9c29c2a6bbbb8410ca50
2020-03-02 16:01:00 -08:00

203 lines
8.1 KiB
C++

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#include <string>
#include "db/dbformat.h"
#include "db/merge_context.h"
#include "db/read_callback.h"
#include "rocksdb/env.h"
#include "rocksdb/statistics.h"
#include "rocksdb/types.h"
#include "table/block_based/block.h"
namespace ROCKSDB_NAMESPACE {
class MergeContext;
class PinnedIteratorsManager;
// Data structure for accumulating statistics during a point lookup. At the
// end of the point lookup, the corresponding ticker stats are updated. This
// avoids the overhead of frequent ticker stats updates
struct GetContextStats {
uint64_t num_cache_hit = 0;
uint64_t num_cache_index_hit = 0;
uint64_t num_cache_data_hit = 0;
uint64_t num_cache_filter_hit = 0;
uint64_t num_cache_compression_dict_hit = 0;
uint64_t num_cache_index_miss = 0;
uint64_t num_cache_filter_miss = 0;
uint64_t num_cache_data_miss = 0;
uint64_t num_cache_compression_dict_miss = 0;
uint64_t num_cache_bytes_read = 0;
uint64_t num_cache_miss = 0;
uint64_t num_cache_add = 0;
uint64_t num_cache_bytes_write = 0;
uint64_t num_cache_index_add = 0;
uint64_t num_cache_index_bytes_insert = 0;
uint64_t num_cache_data_add = 0;
uint64_t num_cache_data_bytes_insert = 0;
uint64_t num_cache_filter_add = 0;
uint64_t num_cache_filter_bytes_insert = 0;
uint64_t num_cache_compression_dict_add = 0;
uint64_t num_cache_compression_dict_bytes_insert = 0;
};
// A class to hold context about a point lookup, such as pointer to value
// slice, key, merge context etc, as well as the current state of the
// lookup. Any user using GetContext to track the lookup result must call
// SaveValue() whenever the internal key is found. This can happen
// repeatedly in case of merge operands. In case the key may exist with
// high probability, but IO is required to confirm and the user doesn't allow
// it, MarkKeyMayExist() must be called instead of SaveValue().
class GetContext {
public:
// Current state of the point lookup. All except kNotFound and kMerge are
// terminal states
enum GetState {
kNotFound,
kFound,
kDeleted,
kCorrupt,
kMerge, // saver contains the current merge result (the operands)
kBlobIndex,
};
GetContextStats get_context_stats_;
// Constructor
// @param value Holds the value corresponding to user_key. If its nullptr
// then return all merge operands corresponding to user_key
// via merge_context
// @param value_found If non-nullptr, set to false if key may be present
// but we can't be certain because we cannot do IO
// @param max_covering_tombstone_seq Pointer to highest sequence number of
// range deletion covering the key. When an internal key
// is found with smaller sequence number, the lookup
// terminates
// @param seq If non-nullptr, the sequence number of the found key will be
// saved here
// @param callback Pointer to ReadCallback to perform additional checks
// for visibility of a key
// @param is_blob_index If non-nullptr, will be used to indicate if a found
// key is of type blob index
// @param do_merge True if value associated with user_key has to be returned
// and false if all the merge operands associated with user_key has to be
// returned. Id do_merge=false then all the merge operands are stored in
// merge_context and they are never merged. The value pointer is untouched.
GetContext(const Comparator* ucmp, const MergeOperator* merge_operator,
Logger* logger, Statistics* statistics, GetState init_state,
const Slice& user_key, PinnableSlice* value,
bool* value_found, MergeContext* merge_context, bool do_merge,
SequenceNumber* max_covering_tombstone_seq, Env* env,
SequenceNumber* seq = nullptr,
PinnedIteratorsManager* _pinned_iters_mgr = nullptr,
ReadCallback* callback = nullptr, bool* is_blob_index = nullptr,
uint64_t tracing_get_id = 0);
GetContext(const Comparator* ucmp, const MergeOperator* merge_operator,
Logger* logger, Statistics* statistics, GetState init_state,
const Slice& user_key, PinnableSlice* value,
std::string* timestamp, bool* value_found,
MergeContext* merge_context, bool do_merge,
SequenceNumber* max_covering_tombstone_seq, Env* env,
SequenceNumber* seq = nullptr,
PinnedIteratorsManager* _pinned_iters_mgr = nullptr,
ReadCallback* callback = nullptr, bool* is_blob_index = nullptr,
uint64_t tracing_get_id = 0);
GetContext() = delete;
// This can be called to indicate that a key may be present, but cannot be
// confirmed due to IO not allowed
void MarkKeyMayExist();
// Records this key, value, and any meta-data (such as sequence number and
// state) into this GetContext.
//
// If the parsed_key matches the user key that we are looking for, sets
// matched to true.
//
// Returns True if more keys need to be read (due to merges) or
// False if the complete value has been found.
bool SaveValue(const ParsedInternalKey& parsed_key, const Slice& value,
bool* matched, Cleanable* value_pinner = nullptr);
// Simplified version of the previous function. Should only be used when we
// know that the operation is a Put.
void SaveValue(const Slice& value, SequenceNumber seq);
GetState State() const { return state_; }
SequenceNumber* max_covering_tombstone_seq() {
return max_covering_tombstone_seq_;
}
PinnedIteratorsManager* pinned_iters_mgr() { return pinned_iters_mgr_; }
// If a non-null string is passed, all the SaveValue calls will be
// logged into the string. The operations can then be replayed on
// another GetContext with replayGetContextLog.
void SetReplayLog(std::string* replay_log) { replay_log_ = replay_log; }
// Do we need to fetch the SequenceNumber for this key?
bool NeedToReadSequence() const { return (seq_ != nullptr); }
bool sample() const { return sample_; }
bool CheckCallback(SequenceNumber seq) {
if (callback_) {
return callback_->IsVisible(seq);
}
return true;
}
void ReportCounters();
bool has_callback() const { return callback_ != nullptr; }
uint64_t get_tracing_get_id() const { return tracing_get_id_; }
void push_operand(const Slice& value, Cleanable* value_pinner);
private:
const Comparator* ucmp_;
const MergeOperator* merge_operator_;
// the merge operations encountered;
Logger* logger_;
Statistics* statistics_;
GetState state_;
Slice user_key_;
PinnableSlice* pinnable_val_;
std::string* timestamp_;
bool* value_found_; // Is value set correctly? Used by KeyMayExist
MergeContext* merge_context_;
SequenceNumber* max_covering_tombstone_seq_;
Env* env_;
// If a key is found, seq_ will be set to the SequenceNumber of most recent
// write to the key or kMaxSequenceNumber if unknown
SequenceNumber* seq_;
std::string* replay_log_;
// Used to temporarily pin blocks when state_ == GetContext::kMerge
PinnedIteratorsManager* pinned_iters_mgr_;
ReadCallback* callback_;
bool sample_;
// Value is true if it's called as part of DB Get API and false if it's
// called as part of DB GetMergeOperands API. When it's false merge operators
// are never merged.
bool do_merge_;
bool* is_blob_index_;
// Used for block cache tracing only. A tracing get id uniquely identifies a
// Get or a MultiGet.
const uint64_t tracing_get_id_;
};
// Call this to replay a log and bring the get_context up to date. The replay
// log must have been created by another GetContext object, whose replay log
// must have been set by calling GetContext::SetReplayLog().
void replayGetContextLog(const Slice& replay_log, const Slice& user_key,
GetContext* get_context,
Cleanable* value_pinner = nullptr);
} // namespace ROCKSDB_NAMESPACE