Summary:
(Based on Yanqin's idea) Add a new field in readoptions as lower timestamp bound for iterator. When the parameter is not supplied (nullptr), the iterator returns the latest visible version of a record. When it is supplied, the existing timestamp field is the upper bound. Together the two serves as a bounded time window. The iterator returns all versions of a record falling in the window.
SeekRandom 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 e860f8840):
seekrandom : 7.836 micros/op 4082449 ops/sec; (0 of 73481999 found)
This PR:
seekrandom : 7.764 micros/op 4120935 ops/sec; (0 of 71303999 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 --statistics=0 --stats_per_interval=0 --stats_interval=1048576 --histogram=0 --use_plain_table=1 --open_files=-1 --memtablerep=prefix_hash --bloom_bits=10 --bloom_locality=1 --duration=600 --benchmarks=seekrandom --use_existing_db=1 --num=25000000 --threads=32 --allow_concurrent_memtable_write=0
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6544
Reviewed By: ltamasi
Differential Revision: D20844069
Pulled By: riversand963
fbshipit-source-id: d97f2bf38a323c8c6a68db213b2d3c694b1c1f74
9e89ffb776