Summary:
Right now, in db_stress, as long as prefix extractor is defined, TestIterator always uses. There is value of cover total_order_seek = true when prefix extractor is define. Add a small chance that this flag is turned on.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6039
Test Plan: Run the test for a while.
Differential Revision: D18539689
fbshipit-source-id: 568790dd7789c9986b83764b870df0423a122d99
Summary:
Right now, crash_test always uses 16KB max_manifest_file_size value. It is good to cover logic of manifest file switch. However, information stored in manifest files might be useful in debugging failures. Switch to only use small manifest file size in 1/15 of the time.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6034
Test Plan: Observe command generated by db_crash_test.py multiple times and see the --max_manifest_file_size value distribution.
Differential Revision: D18513824
fbshipit-source-id: 7b3ae6dbe521a0918df41064e3fa5ecbf2466e04
Summary:
Right now, db_stress doesn't cover SeekForPrev(). Add the coverage, which mirrors what we do for Seek().
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6022
Test Plan: Run "make crash_test". Do some manual source code hack to simular iterator wrong results and see it caught.
Differential Revision: D18442193
fbshipit-source-id: 879b79000d5e33c625c7e970636de191ccd7776c
Summary:
In stress test, all iterator verification is turned off is lower bound is enabled. This might be stricter than needed. This PR relaxes the condition and include the case where lower bound is lower than both of seek key and upper bound. It seems to work mostly fine when I run crash test locally.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5869
Test Plan: Run crash_test
Differential Revision: D18363578
fbshipit-source-id: 23d57e11ea507949b8100f4190ddfbe8db052d5a
Summary:
Right now, in db_stress's CF consistency test's TestGet case, if failure happens, we do normal string printing, rather than hex printing, so that some text is not printed out, which makes debugging harder. Fix it by printing hex instead.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5989
Test Plan: Build db_stress and see t passes.
Differential Revision: D18363552
fbshipit-source-id: 09d1b8f6fbff37441cbe7e63a1aef27551226cec
Summary:
In the previous PR https://github.com/facebook/rocksdb/issues/4788, user can use db_bench mix_graph option to generate the workload that is from the social graph. The key is generated based on the key access hotness. In this PR, user can further model the key-range hotness and fit those to two-term-exponential distribution. First, user cuts the whole key space into small key ranges (e.g., key-ranges are the same size and the key-range number is the number of SST files). Then, user calculates the average access count per key of each key-range as the key-range hotness. Next, user fits the key-range hotness to two-term-exponential distribution (f(x) = f(x) = a*exp(b*x) + c*exp(d*x)) and generate the value of a, b, c, and d. They are the parameters in db_bench: prefix_dist_a, prefix_dist_b, prefix_dist_c, and prefix_dist_d. Finally, user can run db_bench by specify the parameters.
For example:
`./db_bench --benchmarks="mixgraph" -use_direct_io_for_flush_and_compaction=true -use_direct_reads=true -cache_size=268435456 -key_dist_a=0.002312 -key_dist_b=0.3467 -keyrange_dist_a=14.18 -keyrange_dist_b=-2.917 -keyrange_dist_c=0.0164 -keyrange_dist_d=-0.08082 -keyrange_num=30 -value_k=0.2615 -value_sigma=25.45 -iter_k=2.517 -iter_sigma=14.236 -mix_get_ratio=0.85 -mix_put_ratio=0.14 -mix_seek_ratio=0.01 -sine_mix_rate_interval_milliseconds=5000 -sine_a=350 -sine_b=0.0105 -sine_d=50000 --perf_level=2 -reads=1000000 -num=5000000 -key_size=48`
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5953
Test Plan: run db_bench with different parameters and checked the results.
Differential Revision: D18053527
Pulled By: zhichao-cao
fbshipit-source-id: 171f8b3142bd76462f1967c58345ad7e4f84bab7
Summary:
DBImpl extends the public GetSnapshot() with GetSnapshotForWriteConflictBoundary() method that takes snapshots specially for write-write conflict checking. Compaction treats such snapshots differently to avoid GCing a value written after that, so that the write conflict remains visible even after the compaction. The patch extends stress tests with such snapshots.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5897
Differential Revision: D17937476
Pulled By: maysamyabandeh
fbshipit-source-id: bd8b0c578827990302194f63ae0181e15752951d
Summary:
This reverts commit 351e25401b.
All branches have been fixed to buildable on FB environments, so we can revert it.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5999
Differential Revision: D18281947
fbshipit-source-id: 6deaaf1b5df2349eee5d6ed9b91208cd7e23ec8e
Summary:
A recent commit make periodic compaction option valid in FIFO, which means TTL. But we fail to disable it in crash test, causing assert failure. Fix it by having it disabled.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5993
Test Plan: Restart "make crash_test" many times and make sure --periodic_compaction_seconds=0 is always the case when --compaction_style=2
Differential Revision: D18263223
fbshipit-source-id: c91a802017d83ae89ac43827d1b0012861933814
Summary:
We have updated earlier release branches going back to 5.5 so they are
built using gcc7 by default. Disabling ancient versions before that
until we figure out a plan for them.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5990
Test Plan: Ran the script locally.
Differential Revision: D18252386
Pulled By: ltamasi
fbshipit-source-id: a7bbb30dc52ff2eaaf31a29ecc79f7cf4e2834dc
Summary:
Recently, pipelined write is enabled even if atomic flush is enabled, which causing sanitizing failure in db_stress. Revert this change.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5986
Test Plan: Run "make crash_test_with_atomic_flush" and see it to run for some while so that the old sanitizing error (which showed up quickly) doesn't show up.
Differential Revision: D18228278
fbshipit-source-id: 27fdf2f8e3e77068c9725a838b9bef4ab25a2553
Summary:
More release branches are created. We should include them in continuous format compatibility checks.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5985
Test Plan: Let's see whether it is passes.
Differential Revision: D18226532
fbshipit-source-id: 75d8cad5b03ccea4ce16f00cea1f8b7893b0c0c8
Summary:
In pipeline writing mode, memtable switching needs to wait for memtable writing to finish to make sure that when memtables are made immutable, inserts are not going to them. This is currently done in DBImpl::SwitchMemtable(). This is done after flush_scheduler_.TakeNextColumnFamily() is called to fetch the list of column families to switch. The function flush_scheduler_.TakeNextColumnFamily() itself, however, is not thread-safe when being called together with flush_scheduler_.ScheduleFlush().
This change provides a fix, which moves the waiting logic before flush_scheduler_.TakeNextColumnFamily(). WaitForPendingWrites() is a natural place where the logic can happen.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5716
Test Plan: Run all tests with ASAN and TSAN.
Differential Revision: D18217658
fbshipit-source-id: b9c5e765c9989645bf10afda7c5c726c3f82f6c3
Summary:
Right now, in db_stress's iterator tests, we always use the same CF to validate iterator results. This commit changes it so that a randomized CF is used in Cf consistency test, where every CF should have exactly the same data. This would help catch more bugs.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5983
Test Plan: Run "make crash_test_with_atomic_flush".
Differential Revision: D18217643
fbshipit-source-id: 3ac998852a0378bb59790b20c5f236f6a5d681fe
Summary:
Right now in CF consitency stres test's TestGet(), keys are just fetched without validation. With this change, in 1/2 the time, compare all the CFs share the same value with the same key.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5863
Test Plan: Run "make crash_test_with_atomic_flush" and see tests pass. Hack the code to generate some inconsistency and observe the test fails as expected.
Differential Revision: D17934206
fbshipit-source-id: 00ba1a130391f28785737b677f80f366fb83cced
Summary:
Since we already parse env_uri from command line and creates custom Env
accordingly, we should invoke the methods of such Envs instead of using
Env::Default().
Test Plan (on devserver):
```
$make db_bench db_stress
$./db_bench -benchmarks=fillseq
./db_stress
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5943
Differential Revision: D18018550
Pulled By: riversand963
fbshipit-source-id: 03b61329aaae0dfd914a0b902cc677f570f102e3
Summary:
Since SeekForPrev (used by Prev) is not supported by HashSkipList when prefix is used, we disable it when stress testing HashSkipList.
- Change the default memtablerep to skip list.
- Avoid Prev() when memtablerep is HashSkipList and prefix is used.
Test Plan (on devserver):
```
$make db_stress
$./db_stress -ops_per_thread=10000 -reopen=1 -destroy_db_initially=true -column_families=1 -threads=1 -column_families=1 -memtablerep=prefix_hash
$# or simply
$./db_stress
$./db_stress -memtablerep=prefix_hash
```
Results must print "Verification successful".
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5942
Differential Revision: D18017062
Pulled By: riversand963
fbshipit-source-id: af867e59aa9e6f533143c984d7d529febf232fd7
Summary:
Plain table SSTs could crash sst_dump because of a bug in
PlainTableReader that can leave table_properties_ as null. Even if it
was intended not to keep the table properties in some cases, they were
leaked on the offending code path.
Steps to reproduce:
$ db_bench --benchmarks=fillrandom --num=2000000 --use_plain_table --prefix-size=12
$ sst_dump --file=0000xx.sst --show_properties
from [] to []
Process /dev/shm/dbbench/000014.sst
Sst file format: plain table
Raw user collected properties
------------------------------
Segmentation fault (core dumped)
Also added missing unit testing of plain table full_scan_mode, and
an assertion in NewIterator to check for regression.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5940
Test Plan: new unit test, manual, make check
Differential Revision: D18018145
Pulled By: pdillinger
fbshipit-source-id: 4310c755e824c4cd6f3f86a3abc20dfa417c5e07
Summary:
In the current trace replay, all the queries are serialized and called by single threads. It may not simulate the original application query situations closely. The multi-threads replay is implemented in this PR. Users can set the number of threads to replay the trace. The queries generated according to the trace records are scheduled in the thread pool job queue.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5934
Test Plan: test with make check and real trace replay.
Differential Revision: D17998098
Pulled By: zhichao-cao
fbshipit-source-id: 87eecf6f7c17a9dc9d7ab29dd2af74f6f60212c8
Summary:
expose db stress test by providing db_stress_tool.h in public header.
This PR does the following:
- adds a new header, db_stress_tool.h, in include/rocksdb/
- renames db_stress.cc to db_stress_tool.cc
- adds a db_stress.cc which simply invokes a test function.
- update Makefile accordingly.
Test Plan (dev server):
```
make db_stress
./db_stress
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5937
Differential Revision: D17997647
Pulled By: riversand963
fbshipit-source-id: 1a8d9994f89ce198935566756947c518f0052410
Summary:
The patch adds a new command line parameter --decode_blob_index to sst_dump.
If this switch is specified, sst_dump prints blob indexes in a human readable format,
printing the blob file number, offset, size, and expiration (if applicable) for blob
references, and the blob value (and expiration) for inlined blobs.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5926
Test Plan:
Used db_bench's BlobDB mode to generate SST files containing blob references with
and without expiration, as well as inlined blobs with and without expiration (note: the
latter are stored as plain values), and confirmed sst_dump correctly prints all four types
of records.
Differential Revision: D17939077
Pulled By: ltamasi
fbshipit-source-id: edc5f58fee94ba35f6699c6a042d5758f5b3963d
Summary:
Currently, db_bench only supports PutWithTTL operations for BlobDB but
not regular Puts. The patch adds support for regular (non-TTL) Puts and also
changes the default for blob_db_max_ttl_range to zero, which corresponds
to no TTL.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5921
Test Plan:
make check
./db_bench -benchmarks=fillrandom -statistics -stats_interval_seconds=1
-duration=90 -num=500000 -use_blob_db=1 -blob_db_file_size=1000000
-target_file_size_base=1000000 (issues Put operations with no TTL)
./db_bench -benchmarks=fillrandom -statistics -stats_interval_seconds=1
-duration=90 -num=500000 -use_blob_db=1 -blob_db_file_size=1000000
-target_file_size_base=1000000 -blob_db_max_ttl_range=86400 (issues
PutWithTTL operations with random TTLs in the [0, blob_db_max_ttl_range)
interval, as before)
Differential Revision: D17919798
Pulled By: ltamasi
fbshipit-source-id: b946c3522b836b92b4c157ffbad24f92ba2b0a16
Summary:
The loop in OperateDb() is getting quite complicated with the introduction of multiple key operations such as MultiGet and Reseeks. This is resulting in a number of corner cases that hangs db_stress due to synchronization problems during reopen (i.e when -reopen=<> option is specified). This PR makes it more robust by ensuring all db_stress threads vote to reopen the DB the exact same number of times.
Most of the changes in this diff are due to indentation.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5893
Test Plan: Run crash test
Differential Revision: D17823827
Pulled By: anand1976
fbshipit-source-id: ec893829f611ac7cac4057c0d3d99f9ffb6a6dd9
Summary:
This PR allows for the creation of custom env when using sst_dump. If
the user does not set options.env or set options.env to nullptr, then sst_dump
will automatically try to create a custom env depending on the path to the sst
file or db directory. In order to use this feature, the user must call
ObjectRegistry::Register() beforehand.
Test Plan (on devserver):
```
$make all && make check
```
All tests must pass to ensure this change does not break anything.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5845
Differential Revision: D17678038
Pulled By: riversand963
fbshipit-source-id: 58ecb4b3f75246d52b07c4c924a63ee61c1ee626
Summary:
This is the 2nd attempt after the revert of https://github.com/facebook/rocksdb/pull/4020
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5895
Test Plan:
```
./tools/db_crashtest.py blackbox --simple --interval=10 --max_key=10000000
```
Differential Revision: D17822137
Pulled By: maysamyabandeh
fbshipit-source-id: 3d148c0d8cc129080410ff859c04b544223c8ea3
Summary:
When multiple operations are performed in a db_stress thread in one loop
iteration, the reopen voting logic needs to take that into account. It
was doing that for MultiGet, but a new option was introduced recently to
do multiple iterator seeks per iteration, which broke it again. Fix the
logic to be more robust and agnostic of the type of operation performed.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5876
Test Plan: Run db_stress
Differential Revision: D17733590
Pulled By: anand1976
fbshipit-source-id: 787f01abefa1e83bba43e0b4f4abb26699b2089e
Summary:
Two more bug fixes in db_stress:
1. this is to complete the fix of the regression bug causing overflowing when supporting FLAGS_prefix_size = -1.
2. Fix regression bug in compare iterator itself:
(1) when creating control iterator, which used the same read option as the normal iterator by mistake; (2) the logic of comparing has some problems. Fix them.
(3) disable validation for lower bound now, which generated some wildly different results. Disabling it to make normal tests pass while investigating it.
3. Cleaning up snapshots in verification failure cases. Memory is leaked otherwise.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5867
Test Plan: Run "make crash_test" for a while and see at least 1 is fixed.
Differential Revision: D17671712
fbshipit-source-id: 011f98ea1a72aef23e19ff28656830c78699b402
Summary:
When prefix_size = -1, stress test crashes with run time error because of overflow. Fix it by not using -1 but 7 in prefix scan mode.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5862
Test Plan:
Run
python -u tools/db_crashtest.py --simple whitebox --random_kill_odd \
888887 --compression_type=zstd
and see it doesn't crash.
Differential Revision: D17642313
fbshipit-source-id: f029e7651498c905af1b1bee6d310ae50cdcda41
Summary:
For now, crash_test is not able to report any failure for the logic related to iterator upper, lower bounds or iterators, or reseek. These are features prone to errors. Improve db_stress in several ways:
(1) For each iterator run, reseek up to 3 times.
(2) For every iterator, create control iterator with upper or lower bound, with total order seek. Compare the results with the iterator.
(3) Make simple crash test to avoid prefix size to have more coverage.
(4) make prefix_size = 0 a valid size and -1 to indicate disabling prefix extractor.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5846
Test Plan: Manually hack the code to create wrong results and see they are caught by the tool.
Differential Revision: D17631760
fbshipit-source-id: acd460a177bd2124a5ffd7fff490702dba63030b
Summary:
Further apply formatter to more recent commits.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5830
Test Plan: Run all existing tests.
Differential Revision: D17488031
fbshipit-source-id: 137458fd94d56dd271b8b40c522b03036943a2ab
Summary:
Some recent commits might not have passed through the formatter. I formatted recent 45 commits. The script hangs for more commits so I stopped there.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5827
Test Plan: Run all existing tests.
Differential Revision: D17483727
fbshipit-source-id: af23113ee63015d8a43d89a3bc2c1056189afe8f
Summary:
PR https://github.com/facebook/rocksdb/issues/4020 enabled partitioned indexes/filters in stress tests; however,
this causes assertion failures in BatchedOpsStressTest. This patch
disables them until we can root cause the failures.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5811
Test Plan: Ran the script and made sure it only uses the binary search index.
Differential Revision: D17399366
Pulled By: ltamasi
fbshipit-source-id: adb116e6297f9c6ccd7ac15b6a16c9aa91f21ac5
Summary:
file_reader_writer.h and .cc contain several files and helper function, and it's hard to navigate. Separate it to multiple files and put them under file/
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5803
Test Plan: Build whole project using make and cmake.
Differential Revision: D17374550
fbshipit-source-id: 10efca907721e7a78ed25bbf74dc5410dea05987
Summary:
PR https://github.com/facebook/rocksdb/issues/4020 implicitly enabled the hash index as well in stress/crash
tests, resulting in assertion failures in Block. This patch disables
the hash index until we can pinpoint the root cause of these issues.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5792
Test Plan:
Ran tools/db_crashtest.py and made sure it only uses index types 0 and 2
(binary search and partitioned index).
Differential Revision: D17346777
Pulled By: ltamasi
fbshipit-source-id: b4318f37f1fda3ee1bbff4ef2c2f556ca9e6b551
Summary:
This is required to compile on Windows with Visual Studio 2015.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5786
Differential Revision: D17335994
fbshipit-source-id: 8f9568310bc6f697e312b5e24ad465e9084f0011
Summary:
- In `db_stress`, support choosing index type and whether to enable filter partitioning, and randomly set those options in crash test
- When partitioned filter is enabled by crash test, force partitioned index to also be enabled since it's a prerequisite
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4020
Test Plan:
currently this is blocked on fixing the bug that crash test caught:
```
$ TEST_TMPDIR=/data/compaction_bench python ./tools/db_crashtest.py blackbox --simple --interval=10 --max_key=10000000
...
Verification failed for column family 0 key 937501: Value not found: NotFound:
Crash-recovery verification failed :(
```
Differential Revision: D8508683
Pulled By: maysamyabandeh
fbshipit-source-id: 0337e5d0558bcef26b1f3699f47265a2c1e99629
Summary:
https://github.com/facebook/rocksdb/pull/5741 added compaction TTL to crash test, but it causes assertion fails for FIFO compaction. Disable this combination for now while we debug the assertion failure.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5749
Test Plan: Run crash test and observe that when compaction_style=2, compaction_ttl is always 0.
Differential Revision: D17078292
fbshipit-source-id: 446821a3b9739956094d5e4f9be1251a15b57f5d
Summary:
Covering periodic compaction and compaction TTL can help us expose potential issues. Add it there.
Randomly select value for these two options.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5741
Test Plan: Run crash_test and see the perameters generated.
Differential Revision: D17059515
fbshipit-source-id: 8213974846a0b6a22fc13be705825c9054d1d097
Summary:
MyRocks currently sets `max_write_buffer_number_to_maintain` in order to maintain enough history for transaction conflict checking. The effectiveness of this approach depends on the size of memtables. When memtables are small, it may not keep enough history; when memtables are large, this may consume too much memory.
We are proposing a new way to configure memtable list history: by limiting the memory usage of immutable memtables. The new option is `max_write_buffer_size_to_maintain` and it will take precedence over the old `max_write_buffer_number_to_maintain` if they are both set to non-zero values. The new option accounts for the total memory usage of flushed immutable memtables and mutable memtable. When the total usage exceeds the limit, RocksDB may start dropping immutable memtables (which is also called trimming history), starting from the oldest one.
The semantics of the old option actually works both as an upper bound and lower bound. History trimming will start if number of immutable memtables exceeds the limit, but it will never go below (limit-1) due to history trimming.
In order the mimic the behavior with the new option, history trimming will stop if dropping the next immutable memtable causes the total memory usage go below the size limit. For example, assuming the size limit is set to 64MB, and there are 3 immutable memtables with sizes of 20, 30, 30. Although the total memory usage is 80MB > 64MB, dropping the oldest memtable will reduce the memory usage to 60MB < 64MB, so in this case no memtable will be dropped.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5022
Differential Revision: D14394062
Pulled By: miasantreble
fbshipit-source-id: 60457a509c6af89d0993f988c9b5c2aa9e45f5c5
Summary:
AtomicFlushStressTest is a powerful test, but right now we only run it for atomic_flush=true + disable_wal=true. We further extend it to the case where atomic_flush=false + disable_wal = false. All the workload generation and validation can stay the same.
Atomic flush crash test is also changed to switch between the two test scenarios. It makes the name "atomic flush crash test" out of sync from what it really does. We leave it as it is to avoid troubles with continous test set-up.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5729
Test Plan: Run "CRASH_TEST_KILL_ODD=188 TEST_TMPDIR=/dev/shm/ USE_CLANG=1 make whitebox_crash_test_with_atomic_flush", observe the settings used and see it passed.
Differential Revision: D16969791
fbshipit-source-id: 56e37487000ae631e31b0100acd7bdc441c04163
Summary:
Atomic white box test's kill odd is the same as normal test. However, in the scenario that only WritableFileWriter::Append() is blacklisted, WritableFileWriter::Flush() dominates the killing odds. Normally, most of WritableFileWriter::Flush() are called in WAL writes, where every write triggers a WAL flush. In atomic test, WAL is disabled, so the kill happens less frequently than we antipated. In some rare cases, the kill didn't end up with happening (for reasons I still don't fully understand) and cause the stress test timeout.
If WAL is disabled, make the odds 5x likely to trigger.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5717
Test Plan: Run whitebox_crash_test_with_atomic_flush and whitebox_crash_test and observe the kill odds printed out.
Differential Revision: D16897237
fbshipit-source-id: cbf5d96f6fc0e980523d0f1f94bf4e72cdb82d1c
Summary:
Right now VerifyChecksum() doesn't do read-ahead. In some use cases, users won't be able to achieve good performance. With this change, by default, RocksDB will do a default readahead, and users will be able to overwrite the readahead size by passing in a ReadOptions.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5713
Test Plan: Add a new unit test.
Differential Revision: D16860874
fbshipit-source-id: 0cff0fe79ac855d3d068e6ccd770770854a68413
