rocksdb/utilities/transactions/snapshot_checker.cc
Maysam Yabandeh 14b3f683a1 WriteUnPrepared: less virtual in iterator callback (#5049)
Summary:
WriteUnPrepared adds a virtual function, MaxUnpreparedSequenceNumber, to ReadCallback, which returns 0 unless WriteUnPrepared is enabled and the transaction has uncommitted data written to the DB. Together with snapshot sequence number, this determines the last sequence that is visible to reads.
The patch clarifies the guarantees of the GetIterator API in WriteUnPrepared transactions and make use of that to statically initialize the read callback and thus avoid the virtual call.
Furthermore it increases the minimum value for min_uncommitted from 0 to 1 as seq 0 is used only for last level keys that are committed in all snapshots.

The following benchmark shows +0.26% higher throughput in seekrandom benchmark.

Benchmark:
./db_bench --benchmarks=fillrandom --use_existing_db=0 --num=1000000 --db=/dev/shm/dbbench

./db_bench --benchmarks=seekrandom[X10] --use_existing_db=1 --db=/dev/shm/dbbench --num=1000000 --duration=60 --seek_nexts=100
seekrandom [AVG    10 runs] : 20355 ops/sec;  225.2 MB/sec
seekrandom [MEDIAN 10 runs] : 20425 ops/sec;  225.9 MB/sec

./db_bench_lessvirtual3 --benchmarks=seekrandom[X10] --use_existing_db=1 --db=/dev/shm/dbbench --num=1000000 --duration=60 --seek_nexts=100
seekrandom [AVG    10 runs] : 20409 ops/sec;  225.8 MB/sec
seekrandom [MEDIAN 10 runs] : 20487 ops/sec;  226.6 MB/sec
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5049

Differential Revision: D14366459

Pulled By: maysamyabandeh

fbshipit-source-id: ebaff8908332a5ae9af7defeadabcb624be660ef
2019-04-02 14:47:16 -07:00

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1.6 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).
#include "db/snapshot_checker.h"
#ifdef ROCKSDB_LITE
#include <assert.h>
#endif // ROCKSDB_LITE
#include "utilities/transactions/write_prepared_txn_db.h"
namespace rocksdb {
#ifdef ROCKSDB_LITE
WritePreparedSnapshotChecker::WritePreparedSnapshotChecker(
WritePreparedTxnDB* /*txn_db*/) {}
SnapshotCheckerResult WritePreparedSnapshotChecker::CheckInSnapshot(
SequenceNumber /*sequence*/, SequenceNumber /*snapshot_sequence*/) const {
// Should never be called in LITE mode.
assert(false);
return SnapshotCheckerResult::kInSnapshot;
}
#else
WritePreparedSnapshotChecker::WritePreparedSnapshotChecker(
WritePreparedTxnDB* txn_db)
: txn_db_(txn_db){};
SnapshotCheckerResult WritePreparedSnapshotChecker::CheckInSnapshot(
SequenceNumber sequence, SequenceNumber snapshot_sequence) const {
bool snapshot_released = false;
// TODO(myabandeh): set min_uncommitted
bool in_snapshot = txn_db_->IsInSnapshot(
sequence, snapshot_sequence, kMinUnCommittedSeq, &snapshot_released);
if (snapshot_released) {
return SnapshotCheckerResult::kSnapshotReleased;
}
return in_snapshot ? SnapshotCheckerResult::kInSnapshot
: SnapshotCheckerResult::kNotInSnapshot;
}
#endif // ROCKSDB_LITE
DisableGCSnapshotChecker DisableGCSnapshotChecker::instance_;
} // namespace rocksdb