rocksdb/db
anand76 fefd4b98c5 Introduce a new MultiGet batching implementation (#5011)
Summary:
This PR introduces a new MultiGet() API, with the underlying implementation grouping keys based on SST file and batching lookups in a file. The reason for the new API is twofold - the definition allows callers to allocate storage for status and values on stack instead of std::vector, as well as return values as PinnableSlices in order to avoid copying, and it keeps the original MultiGet() implementation intact while we experiment with batching.

Batching is useful when there is some spatial locality to the keys being queries, as well as larger batch sizes. The main benefits are due to -
1. Fewer function calls, especially to BlockBasedTableReader::MultiGet() and FullFilterBlockReader::KeysMayMatch()
2. Bloom filter cachelines can be prefetched, hiding the cache miss latency

The next step is to optimize the binary searches in the level_storage_info, index blocks and data blocks, since we could reduce the number of key comparisons if the keys are relatively close to each other. The batching optimizations also need to be extended to other formats, such as PlainTable and filter formats. This also needs to be added to db_stress.

Benchmark results from db_bench for various batch size/locality of reference combinations are given below. Locality was simulated by offsetting the keys in a batch by a stride length. Each SST file is about 8.6MB uncompressed and key/value size is 16/100 uncompressed. To focus on the cpu benefit of batching, the runs were single threaded and bound to the same cpu to eliminate interference from other system events. The results show a 10-25% improvement in micros/op from smaller to larger batch sizes (4 - 32).

Batch   Sizes

1        | 2        | 4         | 8      | 16  | 32

Random pattern (Stride length 0)
4.158 | 4.109 | 4.026 | 4.05 | 4.1 | 4.074        - Get
4.438 | 4.302 | 4.165 | 4.122 | 4.096 | 4.075 - MultiGet (no batching)
4.461 | 4.256 | 4.277 | 4.11 | 4.182 | 4.14        - MultiGet (w/ batching)

Good locality (Stride length 16)
4.048 | 3.659 | 3.248 | 2.99 | 2.84 | 2.753
4.429 | 3.728 | 3.406 | 3.053 | 2.911 | 2.781
4.452 | 3.45 | 2.833 | 2.451 | 2.233 | 2.135

Good locality (Stride length 256)
4.066 | 3.786 | 3.581 | 3.447 | 3.415 | 3.232
4.406 | 4.005 | 3.644 | 3.49 | 3.381 | 3.268
4.393 | 3.649 | 3.186 | 2.882 | 2.676 | 2.62

Medium locality (Stride length 4096)
4.012 | 3.922 | 3.768 | 3.61 | 3.582 | 3.555
4.364 | 4.057 | 3.791 | 3.65 | 3.57 | 3.465
4.479 | 3.758 | 3.316 | 3.077 | 2.959 | 2.891

dbbench command used (on a DB with 4 levels, 12 million keys)-
TEST_TMPDIR=/dev/shm numactl -C 10  ./db_bench.tmp -use_existing_db=true -benchmarks="readseq,multireadrandom" -write_buffer_size=4194304 -target_file_size_base=4194304 -max_bytes_for_level_base=16777216 -num=12000000 -reads=12000000 -duration=90 -threads=1 -compression_type=none -cache_size=4194304000 -batch_size=32 -disable_auto_compactions=true -bloom_bits=10 -cache_index_and_filter_blocks=true -pin_l0_filter_and_index_blocks_in_cache=true -multiread_batched=true -multiread_stride=4
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5011

Differential Revision: D14348703

Pulled By: anand1976

fbshipit-source-id: 774406dab3776d979c809522a67bedac6c17f84b
2019-04-11 14:28:26 -07:00
..
builder.cc Periodic Compactions (#5166) 2019-04-10 19:31:18 -07:00
builder.h Periodic Compactions (#5166) 2019-04-10 19:31:18 -07:00
c_test.c Get CompactionJobInfo from CompactFiles 2018-12-13 14:21:24 -08:00
c.cc Add missing C API for transaction (#5077) 2019-03-19 09:43:22 -07:00
column_family_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
column_family.cc Add DBOptions. avoid_unnecessary_blocking_io to defer file deletions (#5043) 2019-04-01 17:10:40 -07:00
column_family.h Lock free MultiGet (#4754) 2019-01-02 11:42:54 -08:00
compact_files_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
compacted_db_impl.cc move dump stats to a separate thread (#4382) 2018-10-08 22:54:43 -07:00
compacted_db_impl.h Enable checkpoint of read-only db (#4681) 2018-12-07 17:06:02 -08:00
compaction_iteration_stats.h add counter for deletion dropping optimization 2017-08-19 14:10:08 -07:00
compaction_iterator_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
compaction_iterator.cc WritePrepared: relax assert in compaction iterator (#4969) 2019-02-11 15:01:46 -08:00
compaction_iterator.h Deprecate CompactionFilter::IgnoreSnapshots() = false (#4954) 2019-02-07 16:57:33 -08:00
compaction_job_stats_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
compaction_job_test.cc Collect compaction stats by priority and dump to info LOG (#5050) 2019-03-19 17:28:19 -07:00
compaction_job.cc Periodic Compactions (#5166) 2019-04-10 19:31:18 -07:00
compaction_job.h Collect compaction stats by priority and dump to info LOG (#5050) 2019-03-19 17:28:19 -07:00
compaction_picker_fifo.cc Deprecate ttl option from CompactionOptionsFIFO (#4965) 2019-02-15 09:51:41 -08:00
compaction_picker_fifo.h Move FIFOCompactionPicker to a separate file (#4724) 2018-11-29 16:04:52 -08:00
compaction_picker_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
compaction_picker_universal.cc Add two more StatsLevel (#5027) 2019-02-28 10:27:59 -08:00
compaction_picker_universal.h Delete triggered compaction for universal style 2018-05-29 15:44:34 -07:00
compaction_picker.cc Periodic Compactions (#5166) 2019-04-10 19:31:18 -07:00
compaction_picker.h Move FIFOCompactionPicker to a separate file (#4724) 2018-11-29 16:04:52 -08:00
compaction.cc Dictionary compression for files written by SstFileWriter (#4978) 2019-02-14 11:23:55 -08:00
compaction.h Truncate range tombstones by leveraging InternalKeys (#4432) 2018-10-09 15:19:38 -07:00
comparator_db_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
convenience.cc Update all unique/shared_ptr instances to be qualified with namespace std (#4638) 2018-11-09 11:19:58 -08:00
corruption_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
cuckoo_table_db_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
db_basic_test.cc Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
db_blob_index_test.cc fix lite build 2017-10-17 08:57:09 -07:00
db_block_cache_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
db_bloom_filter_test.cc add whole key bloom filter support in memtables (#4985) 2019-02-19 12:15:39 -08:00
db_compaction_filter_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
db_compaction_test.cc Periodic Compactions (#5166) 2019-04-10 19:31:18 -07:00
db_dynamic_level_test.cc Fix flaky DBDynamicLevelTest.DynamicLevelMaxBytesBase2 (#4668) 2018-11-12 16:42:16 -08:00
db_encryption_test.cc Update all unique/shared_ptr instances to be qualified with namespace std (#4638) 2018-11-09 11:19:58 -08:00
db_filesnapshot.cc Remove redundant member var and set options (#4631) 2018-11-12 12:24:26 -08:00
db_flush_test.cc Improve flushing multiple column families (#4708) 2018-12-13 15:12:40 -08:00
db_impl_compaction_flush.cc Fix many bugs in log statement arguments (#5089) 2019-04-04 12:12:11 -07:00
db_impl_debug.cc Expose DB methods to lock and unlock the WAL (#5146) 2019-04-06 06:40:36 -07:00
db_impl_experimental.cc Update JobContext. (#3949) 2018-08-03 17:42:34 -07:00
db_impl_files.cc Smooth the deletion of WAL files (#5116) 2019-03-28 15:17:13 -07:00
db_impl_open.cc Periodic Compactions (#5166) 2019-04-10 19:31:18 -07:00
db_impl_readonly.cc Add two more StatsLevel (#5027) 2019-02-28 10:27:59 -08:00
db_impl_readonly.h Apply automatic formatting to some files (#5114) 2019-03-27 16:24:45 -07:00
db_impl_secondary.cc Support for single-primary, multi-secondary instances (#4899) 2019-03-26 16:45:31 -07:00
db_impl_secondary.h Support for single-primary, multi-secondary instances (#4899) 2019-03-26 16:45:31 -07:00
db_impl_write.cc Fix many bugs in log statement arguments (#5089) 2019-04-04 12:12:11 -07:00
db_impl.cc Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
db_impl.h Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
db_info_dumper.cc avoid copying when iterating using range-based for (#4459) 2018-10-09 17:15:51 -07:00
db_info_dumper.h Change RocksDB License 2017-07-15 16:11:23 -07:00
db_inplace_update_test.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
db_io_failure_test.cc Disable DBIOFailureTest.NoSpaceCompactRange in LITE (#4596) 2018-10-29 14:36:31 -07:00
db_iter_stress_test.cc Move prefix_extractor to MutableCFOptions 2018-05-21 14:43:11 -07:00
db_iter_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
db_iter.cc WriteUnPrepared: less virtual in iterator callback (#5049) 2019-04-02 14:47:16 -07:00
db_iter.h Remove v1 RangeDelAggregator (#4778) 2018-12-17 17:33:46 -08:00
db_iterator_test.cc Fix race condition in IteratorWithLocalStatistics (#5149) 2019-04-03 16:04:38 -07:00
db_log_iter_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
db_memtable_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
db_merge_operator_test.cc WriteUnPrepared: less virtual in iterator callback (#5049) 2019-04-02 14:47:16 -07:00
db_options_test.cc Update RepeatableThreadTest with MockTimeEnv (#5107) 2019-03-29 10:08:50 -07:00
db_properties_test.cc Deprecate ttl option from CompactionOptionsFIFO (#4965) 2019-02-15 09:51:41 -08:00
db_range_del_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
db_secondary_test.cc Support for single-primary, multi-secondary instances (#4899) 2019-03-26 16:45:31 -07:00
db_sst_test.cc Update RepeatableThreadTest with MockTimeEnv (#5107) 2019-03-29 10:08:50 -07:00
db_statistics_test.cc Make statistics's stats_level change thread-safe (#5030) 2019-03-01 10:42:09 -08:00
db_table_properties_test.cc Allow dynamic modification of window size and deletion trigger (#4403) 2018-09-20 15:15:28 -07:00
db_tailing_iter_test.cc Remove managed iterator 2018-07-17 14:43:18 -07:00
db_test2.cc Change OptimizeForPointLookup() and OptimizeForSmallDb() (#5165) 2019-04-11 10:45:36 -07:00
db_test_util.cc Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
db_test_util.h Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
db_test.cc Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
db_universal_compaction_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
db_wal_test.cc Preload some files even if options.max_open_files (#3340) 2018-12-28 18:02:28 -08:00
db_write_test.cc Expose DB methods to lock and unlock the WAL (#5146) 2019-04-06 06:40:36 -07:00
dbformat_test.cc Relax VersionStorageInfo::GetOverlappingInputs check (#4050) 2018-07-13 17:42:38 -07:00
dbformat.cc Apply automatic formatting to some files (#5114) 2019-03-27 16:24:45 -07:00
dbformat.h Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
deletefile_test.cc add assert to silence clang analyzer and fix variable shadowing (#5140) 2019-04-02 21:15:44 -07:00
error_handler_test.cc Fix regression test failures introduced by PR #4164 (#4375) 2018-09-17 13:14:07 -07:00
error_handler.cc Fix typos in comments (#4456) 2018-10-04 20:46:50 -07:00
error_handler.h Fix typos in comments (#4456) 2018-10-04 20:46:50 -07:00
event_helpers.cc Auto recovery from out of space errors (#4164) 2018-09-15 13:43:04 -07:00
event_helpers.h Auto recovery from out of space errors (#4164) 2018-09-15 13:43:04 -07:00
experimental.cc comment unused parameters to turn on -Wunused-parameter flag 2018-04-12 17:59:16 -07:00
external_sst_file_basic_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
external_sst_file_ingestion_job.cc Collect compaction stats by priority and dump to info LOG (#5050) 2019-03-19 17:28:19 -07:00
external_sst_file_ingestion_job.h Atomic ingest (#4895) 2019-02-12 19:16:17 -08:00
external_sst_file_test.cc Refactor ExternalSSTFileTest (#5129) 2019-04-08 11:16:34 -07:00
fault_injection_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
file_indexer_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
file_indexer.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
file_indexer.h Change RocksDB License 2017-07-15 16:11:23 -07:00
filename_test.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
flush_job_test.cc Collect compaction stats by priority and dump to info LOG (#5050) 2019-03-19 17:28:19 -07:00
flush_job.cc Periodic Compactions (#5166) 2019-04-10 19:31:18 -07:00
flush_job.h Collect compaction stats by priority and dump to info LOG (#5050) 2019-03-19 17:28:19 -07:00
flush_scheduler.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
flush_scheduler.h Change RocksDB License 2017-07-15 16:11:23 -07:00
forward_iterator_bench.cc Per-thread unique test db names (#4135) 2018-07-13 17:27:39 -07:00
forward_iterator.cc Add DBOptions. avoid_unnecessary_blocking_io to defer file deletions (#5043) 2019-04-01 17:10:40 -07:00
forward_iterator.h Comment out unused variables 2018-03-05 13:13:41 -08:00
in_memory_stats_history.cc add GetStatsHistory to retrieve stats snapshots (#4748) 2019-02-20 15:52:54 -08:00
in_memory_stats_history.h add GetStatsHistory to retrieve stats snapshots (#4748) 2019-02-20 15:52:54 -08:00
internal_stats.cc Collect compaction stats by priority and dump to info LOG (#5050) 2019-03-19 17:28:19 -07:00
internal_stats.h Collect compaction stats by priority and dump to info LOG (#5050) 2019-03-19 17:28:19 -07:00
job_context.h WritePrepared: Fix visible key compacted out by compaction (#4883) 2019-01-15 21:34:38 -08:00
listener_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
log_format.h Fix an inaccurate comment (#4315) 2018-08-24 18:13:20 -07:00
log_reader.cc Support for single-primary, multi-secondary instances (#4899) 2019-03-26 16:45:31 -07:00
log_reader.h Remove some "using std::..." from header files. (#5113) 2019-03-27 10:28:21 -07:00
log_test.cc Support for single-primary, multi-secondary instances (#4899) 2019-03-26 16:45:31 -07:00
log_writer.cc Remove some "using std::..." from header files. (#5113) 2019-03-27 10:28:21 -07:00
log_writer.h Remove some "using std::..." from header files. (#5113) 2019-03-27 10:28:21 -07:00
logs_with_prep_tracker.cc Skip deleted WALs during recovery 2018-05-03 15:43:09 -07:00
logs_with_prep_tracker.h Skip deleted WALs during recovery 2018-05-03 15:43:09 -07:00
lookup_key.h Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
malloc_stats.cc Detect if Jemalloc is linked with the binary (#4844) 2019-01-03 16:30:12 -08:00
malloc_stats.h Change RocksDB License 2017-07-15 16:11:23 -07:00
manual_compaction_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
memtable_list_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
memtable_list.cc Avoid using kInAtomicGroup tag for single-cf op (#4981) 2019-02-13 18:33:42 -08:00
memtable_list.h Use correct FileMeta for atomic flush result install (#4932) 2019-01-31 14:49:51 -08:00
memtable.cc Consolidate hash function used for non-persistent data in a new function (#5155) 2019-04-08 13:32:06 -07:00
memtable.h add whole key bloom filter support in memtables (#4985) 2019-02-19 12:15:39 -08:00
merge_context.h Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
merge_helper_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
merge_helper.cc Add two more StatsLevel (#5027) 2019-02-28 10:27:59 -08:00
merge_helper.h Remove v1 RangeDelAggregator (#4778) 2018-12-17 17:33:46 -08:00
merge_operator.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
merge_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
obsolete_files_test.cc Improve obsolete_files_test (#5125) 2019-03-28 13:16:02 -07:00
options_file_test.cc Per-thread unique test db names (#4135) 2018-07-13 17:27:39 -07:00
perf_context_test.cc Fix some variable naming in db/transaction_log_impl.* (#5112) 2019-03-27 12:27:54 -07:00
pinned_iterators_manager.h Change RocksDB License 2017-07-15 16:11:23 -07:00
plain_table_db_test.cc Revert "Remove PlainTable's feature store_index_in_file (#4914)" (#5034) 2019-03-01 15:45:45 -08:00
pre_release_callback.h Mark logs with prepare in PreReleaseCallback (#5121) 2019-04-02 15:17:47 -07:00
prefix_test.cc Apply modernize-use-override (2nd iteration) 2019-02-14 14:41:36 -08:00
range_del_aggregator_bench.cc Fix Windows broken build error due to non-const override (#4798) 2018-12-19 13:29:51 -08:00
range_del_aggregator_test.cc Remove v1 RangeDelAggregator (#4778) 2018-12-17 17:33:46 -08:00
range_del_aggregator.cc Remove stale TODO (#4800) 2018-12-19 15:45:37 -08:00
range_del_aggregator.h Fix unused member compile error 2018-12-18 14:28:42 -08:00
range_tombstone_fragmenter_test.cc Prepare FragmentedRangeTombstoneIterator for use in compaction (#4740) 2018-12-11 12:10:48 -08:00
range_tombstone_fragmenter.cc Add compaction logic to RangeDelAggregatorV2 (#4758) 2018-12-17 13:20:51 -08:00
range_tombstone_fragmenter.h Add compaction logic to RangeDelAggregatorV2 (#4758) 2018-12-17 13:20:51 -08:00
read_callback.h WriteUnPrepared: less virtual in iterator callback (#5049) 2019-04-02 14:47:16 -07:00
repair_test.cc Acquire lock on DB LOCK file before starting repair. (#4435) 2018-10-12 10:41:54 -07:00
repair.cc Support for single-primary, multi-secondary instances (#4899) 2019-03-26 16:45:31 -07:00
snapshot_checker.h WritePrepared: fix issue with snapshot released during compaction (#4858) 2019-01-16 09:55:32 -08:00
snapshot_impl.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
snapshot_impl.h WriteUnPrepared: less virtual in iterator callback (#5049) 2019-04-02 14:47:16 -07:00
table_cache.cc Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
table_cache.h Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
table_properties_collector_test.cc Feature for sampling and reporting compressibility (#4842) 2019-03-18 12:15:34 -07:00
table_properties_collector.cc Feature for sampling and reporting compressibility (#4842) 2019-03-18 12:15:34 -07:00
table_properties_collector.h Feature for sampling and reporting compressibility (#4842) 2019-03-18 12:15:34 -07:00
transaction_log_impl.cc Fix some variable naming in db/transaction_log_impl.* (#5112) 2019-03-27 12:27:54 -07:00
transaction_log_impl.h Fix some variable naming in db/transaction_log_impl.* (#5112) 2019-03-27 12:27:54 -07:00
version_builder_test.cc Apply modernize-use-override (3) 2019-02-19 13:39:49 -08:00
version_builder.cc Support for single-primary, multi-secondary instances (#4899) 2019-03-26 16:45:31 -07:00
version_builder.h Support for single-primary, multi-secondary instances (#4899) 2019-03-26 16:45:31 -07:00
version_edit_test.cc Add a unit test to Ignorable manfiest record (#4964) 2019-02-11 11:20:24 -08:00
version_edit.cc Add a placeholder in manifest indicating ignorable record (#4960) 2019-02-08 11:33:11 -08:00
version_edit.h Support for single-primary, multi-secondary instances (#4899) 2019-03-26 16:45:31 -07:00
version_set_test.cc Apply modernize-use-override (3) 2019-02-19 13:39:49 -08:00
version_set.cc Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
version_set.h Introduce a new MultiGet batching implementation (#5011) 2019-04-11 14:28:26 -07:00
wal_manager_test.cc Update all unique/shared_ptr instances to be qualified with namespace std (#4638) 2018-11-09 11:19:58 -08:00
wal_manager.cc Smooth the deletion of WAL files (#5116) 2019-03-28 15:17:13 -07:00
wal_manager.h Fix memleak when DB::DeleteFile() 2018-01-11 18:57:33 -08:00
write_batch_base.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
write_batch_internal.h WriteUnPrepared: Add new WAL marker kTypeBeginUnprepareXID (#4069) 2018-06-28 18:58:29 -07:00
write_batch_test.cc Apply modernize-use-override (3) 2019-02-19 13:39:49 -08:00
write_batch.cc Apply modernize-use-override (3) 2019-02-19 13:39:49 -08:00
write_callback_test.cc Mark logs with prepare in PreReleaseCallback (#5121) 2019-04-02 15:17:47 -07:00
write_callback.h Change RocksDB License 2017-07-15 16:11:23 -07:00
write_controller_test.cc Apply modernize-use-override (3) 2019-02-19 13:39:49 -08:00
write_controller.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
write_controller.h Change RocksDB License 2017-07-15 16:11:23 -07:00
write_thread.cc Add more sync point to fix flaky test GroupCommitTest 2018-11-07 14:07:53 -08:00
write_thread.h Fix skip WAL for whole write_group when leader's callback fail (#4838) 2019-01-03 12:40:42 -08:00