Summary: Got it working by some voodoo programming
Test Plan: works!
Reviewers: sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34611
Summary:
One of the commands in the script make_new_version.sh was
incorrect. Fixed it.
Test Plan: Try the script out to verify that it works.
Reviewers: igor, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34791
Summary: Allow GetThreadList() to report the start time of the current operation.
Test Plan:
./db_bench --benchmarks=fillrandom --num=100000 --threads=40 \
--max_background_compactions=10 --max_background_flushes=3 \
--thread_status_per_interval=1000 --key_size=16 --value_size=1000 \
--num_column_families=10
Sample output:
ThreadID ThreadType cfName Operation OP_StartTime State
140338840797248 High Pri column_family_name_000003 Flush 2015/03/09-17:49:59
140338844991552 High Pri column_family_name_000004 Flush 2015/03/09-17:49:59
140338849185856 Low Pri
140338983403584 Low Pri
140339008569408 Low Pri
140338861768768 Low Pri
140338924683328 Low Pri
140338899517504 Low Pri
140338853380160 Low Pri
140338882740288 Low Pri
140338865963072 High Pri column_family_name_000006 Flush 2015/03/09-17:49:59
140338954043456 Low Pri
140338857574464 Low Pri
Reviewers: igor, rven, sdong
Reviewed By: sdong
Subscribers: lgalanis, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34689
Summary: Introduce parameter -read_random_exp_range in db_bench to provide some key skewness in readrandom and multireadrandom benchmarks. It will helpful to cover block cache better.
Test Plan:
Run benchmarks with this new parameter. I can clearly see block cache hit rate change while I increase this value (DB size is about 66MB):
./db_bench --benchmarks=readrandom -statistics -use_existing_db -cache_size=5000000 --read_random_exp_range=0.0
rocksdb.block.cache.data.miss COUNT : 958418
rocksdb.block.cache.data.hit COUNT : 41582
./db_bench --benchmarks=readrandom -statistics -use_existing_db -cache_size=5000000 --read_random_exp_range=5.0
rocksdb.block.cache.data.miss COUNT : 819518
rocksdb.block.cache.data.hit COUNT : 180482
./db_bench --benchmarks=readrandom -statistics -use_existing_db -cache_size=5000000 --read_random_exp_range=10.0
rocksdb.block.cache.data.miss COUNT : 450479
rocksdb.block.cache.data.hit COUNT : 549521
./db_bench --benchmarks=readrandom -statistics -use_existing_db -cache_size=5000000 --read_random_exp_range=20.0
rocksdb.block.cache.data.miss COUNT : 223192
rocksdb.block.cache.data.hit COUNT : 776808
Reviewers: MarkCallaghan, kradhakrishnan, yhchiang, rven, igor
Reviewed By: igor
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D34629
Summary: I want to be able to set this through mongo config.
Test Plan: added unit test
Reviewers: sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34599
Summary:
Single threaded tests -> sync=0 Multi threaded tests -> sync=1 by default unless DB_BENCH_NO_SYNC is defined.
Also added updaterandom and mergerandom with putOperator. I am waiting for some results from udb on this.
Test Plan:
DB_BENCH_NO_SYNC=1 WAL_DIR=/tmp OUTPUT_DIR=/tmp/b DB_DIR=/tmp ./tools/benchmark.sh debug,bulkload,fillseq,overwrite,filluniquerandom,readrandom,readwhilewriting,updaterandom,mergerandom
WAL_DIR=/tmp OUTPUT_DIR=/tmp/b DB_DIR=/tmp ./tools/benchmark.sh debug,bulkload,fillseq,overwrite,filluniquerandom,readrandom,readwhilewriting,updaterandom,mergerandom
Verify sync settings
Reviewers: sdong, MarkCallaghan, igor, rven
Reviewed By: igor, rven
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34185
Summary:
Add --thread_status_per_interval to db_bench, which allows
db_bench to optionally enable print the current thread status
periodically.
Test Plan:
./db_bench --benchmarks=fillrandom --num=100000 --threads=40 --max_background_compactions=10 --max_background_flushes=3 --thread_status_per_interval=1000 --key_size=16 --value_size=1000 --num_column_families=10
Sample output:
ThreadID ThreadType dbName cfName Operation State
140281571770432 Low Pri
140281575964736 High Pri /tmp/rocksdbtest-5297/dbbench column_family_name_000001 Flush
140281710182464 Low Pri /tmp/rocksdbtest-5297/dbbench column_family_name_000008 Compaction
140281638879296 Low Pri /tmp/rocksdbtest-5297/dbbench column_family_name_000007 Compaction
140281592741952 Low Pri
140281580159040 High Pri /tmp/rocksdbtest-5297/dbbench column_family_name_000002 Flush
140281676628032 Low Pri /tmp/rocksdbtest-5297/dbbench column_family_name_000006 Compaction
140281584353344 Low Pri
140281622102080 Low Pri /tmp/rocksdbtest-5297/dbbench column_family_name_000009 Compaction
140281605324864 Low Pri /tmp/rocksdbtest-5297/dbbench column_family_name_000004 Compaction
140281601130560 High Pri /tmp/rocksdbtest-5297/dbbench default Flush
140281596936256 Low Pri
140281588547648 Low Pri
Reviewers: igor, rven, sdong
Reviewed By: rven
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34515
Summary:
* src.mk (LIB_SOURCES): Add this file:
utilities/document/json_document_builder.cc
to avoid link errors.
Blame Rev: D33849
Test Plan: run "make"
Reviewers: ljin, igor.sugak, rven, sdong, igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34593
Summary:
Any time one would modify a dependent of any *test*.cc file,
"make" would fail to rebuild the affected test binaries,
e.g., db_test. That was due to the fact that we deliberately
excluded those test-related files from the definition of SOURCES
and only $(SOURCES) was used to create the automatically-generated
.d dependency files. The fix is to generate a .d file for every
source file.
* src.mk: New file. Defines LIB_SOURCES, MOCK_SOURCES
and TEST_BENCH_SOURCES.
* Makefile: Include src.mk.
Reflect s/SOURCES/LIB_SOURCES/ renaming.
* build_tools/build_detect_platform: Remove the code
that was used to generate SOURCES= and MOCK_SOURCES=
definitions in make_config.mk. Those lists of files
are now hard-coded in src.mk. Hard-coding this list of
sources is desirable, because without that, one risks
including stray .cc files in a build. Not reproducible.
Test Plan:
Touch a file used by db_test's dependent .o files and ensure that
they are all recompiled. Before, none would be:
$ touch db/db_impl.h && make db_test
CC db/db_test.o
CC db/column_family.o
CC db/db_filesnapshot.o
CC db/db_impl.o
CC db/db_impl_debug.o
CC db/db_impl_readonly.o
CC db/forward_iterator.o
CC db/internal_stats.o
CC db/managed_iterator.o
CC db/repair.o
CC db/write_batch.o
CC utilities/compacted_db/compacted_db_impl.o
CC utilities/ttl/db_ttl_impl.o
CC util/ldb_cmd.o
CC util/ldb_tool.o
CC util/sst_dump_tool.o
CC util/xfunc.o
CCLD db_test
Reviewers: ljin, igor.sugak, igor, rven, sdong
Reviewed By: sdong
Subscribers: yhchiang, adamretter, fyrz, dhruba
Differential Revision: https://reviews.facebook.net/D33849
Summary:
The problem appears to be caused by a bug in Mac OS X compiler
(http://llvm.org/bugs/show_bug.cgi?id=15337). We need explicitly construct the
base object std::ostream(std::streambuf*) with nullptr. Otherwise, ostream will
try to delete the underlying streambuf* which apparently is undefined in the
Mac OS X compiler.
https://github.com/facebook/rocksdb/issues/525
Test Plan:
unit test in fbson
make all check
document_db_test (on mac)
Reviewers: IslamAbdelRahman, igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34587
Summary:
For some reason, libstdc++ implements steady_clock::now() using syscall instead of VDSO optimized clock_gettime() when using glibc 2.16 and earlier. This leads to significant performance degradation for users with older glibcs. See bug reported here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59177
We observed this behavior when testing mongo on AWS hosts. Facebook hosts are unaffected since we use glibc2.17 and 2.20.
Revert "Fix timing"
This reverts commit 965d9d50b8.
Revert "Use chrono for timing"
This reverts commit 001ce64dc7.
Test Plan: make check
Reviewers: MarkCallaghan, yhchiang, rven, meyering, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34371
Summary:
When having fixed max_bytes_for_level_base, the ratio of size of largest level and the second one can range from 0 to the multiplier. This makes LSM tree frequently irregular and unpredictable. It can also cause poor space amplification in some cases.
In this improvement (proposed by Igor Kabiljo), we introduce a parameter option.level_compaction_use_dynamic_max_bytes. When turning it on, RocksDB is free to pick a level base in the range of (options.max_bytes_for_level_base/options.max_bytes_for_level_multiplier, options.max_bytes_for_level_base] so that real level ratios are close to options.max_bytes_for_level_multiplier.
Test Plan: New unit tests and pass tests suites including valgrind.
Reviewers: MarkCallaghan, rven, yhchiang, igor, ikabiljo
Reviewed By: ikabiljo
Subscribers: yoshinorim, ikabiljo, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D31437
Summary:
Pre-fetching is a common operation performed by data stores for
disk/flash based systems as part of database startup.
This is part of task 5197184.
Test Plan: Run the newly added unit test
Reviewers: rven, igor, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33933
Summary: I was pretty sure I compiled this before landing, sorry :/
Test Plan: compiles
Reviewers: sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34173
Summary:
This diff fixes a bug introduced by D28521. Read-only backup engine can delete a backup that is later than the latest -- we never check the condition.
I also added a bunch of logging that will help with debugging cases like this in the future.
See more discussion at t6218248.
Test Plan: Added a unit test that was failing before the change. Also, see new LOG file contents: https://phabricator.fb.com/P19738984
Reviewers: benj, sanketh, sumeet, yhchiang, rven, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33897
Summary: adding stdlib to fbson to fix FreeBSD compilation
Test Plan: 4cfccf14f4
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34143
Summary: as title, we have unused variables. this is a short-term solution
Test Plan: compiles
Reviewers: IslamAbdelRahman, sdong, rven
Reviewed By: rven
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34125
Summary:
Summary:
Added a new option to ColumnFamllyOptions - optimize_filters_for_hits. This option can be used in the case where most
accesses to the store are key hits and we dont need to optimize performance for key misses.
This is useful when you have a very large database and most of your lookups succeed. The option allows the store to
not store and use filters in the last level (the largest level which contains data). These filters can take a large amount of
space for large databases (in memory and on-disk). For the last level, these filters are only useful for key misses and not
for key hits. If we are not optimizing for key misses, we can choose to not store these filters for that level.
This option is only provided for BlockBasedTable. We skip the filters when we are compacting
Test Plan:
1. Modified db_test toalso run tests with an additonal option (skip_filters_on_last_level)
2. Added another unit test to db_test which specifically tests that filters are being skipped
Reviewers: rven, igor, sdong
Reviewed By: sdong
Subscribers: lgalanis, yoshinorim, MarkCallaghan, rven, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33717
Summary:
This patch will update the Makefile and source code so that we can build RocksDB successfully on FreeBSD 10 and 11 (64-bit and 32-bit)
I have also encountered some problems when running tests on FreeBSD, I will try to fix them individually in different diffs
Notes:
- FreeBSD uses clang as it's default compiler (http://lists.freebsd.org/pipermail/freebsd-current/2012-September/036480.html)
- GNU C++ compiler have C++ 11 problems on FreeBSD (https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=193528)
- make is not gmake on FreeBSD (http://www.khmere.com/freebsd_book/html/ch01.html)
Test Plan:
Using VMWare Fusion Create 4 VM machines (FreeBSD 11 64-bit, FreeBSD 11 32-bit, FreeBSD 10 64-bit, FreeBSD 10 32-bit)
- pkg install git gmake gflags archivers/snappy
- git clone https://github.com/facebook/rocksdb.git
- apply this patch
- setenv CXX c++
- setenv CPATH /usr/local/include/
- setenv LIBRARY_PATH /usr/local/lib/
- gmake db_bench
- make sure compilation is successful and db_bench is running
- gmake all
- make sure compilation is successful
Reviewers: sdong, igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D33891
Summary: Current clang path in fbcode points to clang 3.5. This diff updates clang path to clang 3.7.
Test Plan:
Make sure clang 3.7 is in use and all tests are passing.
```lang=bash
% USE_CLANG make check
```
Reviewers: meyering, sdong, rven, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34119
Summary:
The LoadDependency function does not take a lock when it runs
and it could be modifying data structures while other threads are
accessing it.
Test Plan: Run TSAN.
Reviewers: igor, sdong
Reviewed By: igor, sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34095
Summary:
When using latest clang (3.6 or 3.7/trunck) rocksdb is failing with many errors. Some errors are uninitialized use errors.
```
...
CC db/log_test.o
util/ldb_cmd.cc:394:16: error: base class 'rocksdb::LDBCommand' is uninitialized when used here to access 'rocksdb::LDBCommand::BuildCmdLineOptions' [-Werror,-Wuninitialized]
BuildCmdLineOptions({ARG_FROM, ARG_TO, ARG_HEX, ARG_KEY_HEX,
^
...
```
```lang=c++
CompactorCommand::CompactorCommand(const vector<string>& params,
const map<string, string>& options, const vector<string>& flags) :
LDBCommand(options, flags, false,
BuildCmdLineOptions({ARG_FROM, ARG_TO, ARG_HEX, ARG_KEY_HEX,
ARG_VALUE_HEX, ARG_TTL})),
null_from_(true), null_to_(true) {
. . .
}
```
For the fourth parameter of the base constructor (`LDBCommand`) we call `BuildCmdLineOptions`, which is a private non-static method of `LDBCommand` base class.
This diff adds missing `static` keyword for `LDBCommand::BuildCmdLineOptions` method.
Test Plan:
Build with trunk clang and make sure all tests are passing.
```lang=bash
% # Have trunk clang present in path.
% ROCKSDB_NO_FBCODE=1 CC=clang CXX=clang++ make check
``
Reviewers: meyering, sdong, rven, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34083
Summary: mac compile is fixed in fbson, so it can be returned back from 7ce1b2c
Test Plan:
make all check
make valgrind_check
Reviewers: golovachalexander, igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D33855
Summary:
When using latest clang (3.6 or 3.7/trunck) rocksdb is failing with many errors. Almost all of them are missing override errors. This diff adds missing override keyword. No manual changes.
Prerequisites: bear and clang 3.5 build with extra tools
```lang=bash
% USE_CLANG=1 bear make all # generate a compilation database http://clang.llvm.org/docs/JSONCompilationDatabase.html
% clang-modernize -p . -include . -add-override
% make format
```
Test Plan:
Make sure all tests are passing.
```lang=bash
% #Use default fb code clang.
% make check
```
Verify less error and no missing override errors.
```lang=bash
% # Have trunk clang present in path.
% ROCKSDB_NO_FBCODE=1 CC=clang CXX=clang++ make
```
Reviewers: igor, kradhakrishnan, rven, meyering, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34077
Summary:
This changes the RocksDB build to share headers provided by MongoDB. It is invoked as:
ROCKSDB_FOR_MONGO=/path/to/mongodb/root make static_lib
Task ID: #
Blame Rev:
Test Plan:
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34071
Summary:
BlockBasedTable pre-fetches the filter and index blocks on Open call.
This is an optimistic optimization targeted for runtime scenario. The
optimization is unnecessary for sst_dump_tool
- Added a provision to disable pre-fetching of index and filter blocks
in BlockBasedTable
- Disabled pre-fetching for the sst_dump tool
Stack for reference :
#01 0x00000000005ed944 in snappy::InternalUncompress<snappy::SnappyArrayWriter> () from /home/engshare/third-party2/snappy/1.0.3/src/snappy-1.0.3/snappy.cc:148
#02 0x00000000005edeee in snappy::RawUncompress () from /home/engshare/third-party2/snappy/1.0.3/src/snappy-1.0.3/snappy.cc:947
#03 0x00000000004e0b4d in rocksdb::UncompressBlockContents () from /data/users/paultuckfield/rocksdb/./util/compression.h:69
#04 0x00000000004e145c in rocksdb::ReadBlockContents () from /data/users/paultuckfield/rocksdb/table/format.cc:334
#05 0x00000000004ca424 in rocksdb::(anonymous namespace)::ReadBlockFromFile () from /data/users/paultuckfield/rocksdb/table/block_based_table_reader.cc:70
#06 0x00000000004cccad in rocksdb::BlockBasedTable::CreateIndexReader () from /data/users/paultuckfield/rocksdb/table/block_based_table_reader.cc:173
#07 0x00000000004d17e5 in rocksdb::BlockBasedTable::Open () from /data/users/paultuckfield/rocksdb/table/block_based_table_reader.cc:553
#08 0x00000000004c8184 in rocksdb::BlockBasedTableFactory::NewTableReader () from /data/users/paultuckfield/rocksdb/table/block_based_table_factory.cc:51
#09 0x0000000000598463 in rocksdb::SstFileReader::NewTableReader () from /data/users/paultuckfield/rocksdb/util/sst_dump_tool.cc:69
#10 0x00000000005986c2 in rocksdb::SstFileReader::SstFileReader () from /data/users/paultuckfield/rocksdb/util/sst_dump_tool.cc:26
#11 0x0000000000599047 in rocksdb::SSTDumpTool::Run () from /data/users/paultuckfield/rocksdb/util/sst_dump_tool.cc:332
#12 0x0000000000409b06 in main () from /data/users/paultuckfield/rocksdb/tools/sst_dump.cc:12
Test Plan:
- Added a unit test to trigger the code.
- Also did some manual verification.
- Passed all unit tests
task #6296048
Reviewers: igor, rven, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34041
Summary:
An old commit (482401) changed DoWrite to use the value of --writes rather
than --num to determine the range for keys. This restores the old and correct
behavior which is to limit it using --num.
Task ID: #6353043
Blame Rev:
Test Plan:
run db_bench
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34065
Summary:
Introduced final keyword to parameters with immutable values and classes
which should not be derived.
Test Plan:
make rocksdbjava
make jtest
Reviewers: yhchiang, adamretter, ankgup87
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D33417
Summary:
In a release build, a member was not being accessed. This
member was only being accessed in a debug build. We now add an accessor
function for this member and the buid succeeds.
Test Plan: build release/unity/debug on linux/mac
Reviewers: sdong, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34035
Summary: See https://www.facebook.com/groups/rocksdb.dev/permalink/718536351578215/. We should enable people to run without warning-as-error, since we break this so often for different compilers.
Test Plan: introduce an warning, compile sucessfully
Reviewers: yhchiang, meyering, igor.sugak, rven, sdong
Reviewed By: sdong
Subscribers: adamretter, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33963
Summary: This causes warnings on OS X
Test Plan: compiles
Reviewers: rven, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33969
Summary: Replaced LevelDb include guards with #pragma once
Test Plan: make all check
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D33939
Summary:
* Updated Makefile to exit `make analyze` with status 1 if scan-build detected any bugs.
* scan-build automatically detects which c++ compiler to use, and some times is uses wrong ones (from $CPP). Added implicit parameters to use $CC and $CXX.
* Added `scan_build_report` directory to .gitignore file.
* Added `scan_build_report` directory to clean target.
Test Plan:
Run `make analyze` and verify that exit status is 1, if there are scan-build bugs detected.
Run `make clean` and verify that files in `scan_build_report` directory are deleted.
After running `make analyze; git status` and verify that no untracked files in `scan_build_report` directory.
Reviewers: meyering, sdong, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33831
Summary:
This diff contains trivial fixes for 6 scan-build warnings:
**db/c_test.c**
`db` variable is never read. Removed assignment.
scan-build report:
http://home.fburl.com/~sugak/latest20/report-9b77d2.html#EndPath
**db/db_iter.cc**
`skipping` local variable is assigned to false. Then in the next switch block the only "non return" case assign `skipping` to true, the rest cases don't use it and all do return.
scan-build report:
http://home.fburl.com/~sugak/latest20/report-13fca7.html#EndPath
**db/log_reader.cc**
In `bool Reader::SkipToInitialBlock()` `offset_in_block` local variable is assigned to 0 `if (offset_in_block > kBlockSize - 6)` and then never used. Removed the assignment and renamed it to `initial_offset_in_block` to avoid confusion.
scan-build report:
http://home.fburl.com/~sugak/latest20/report-a618dd.html#EndPath
In `bool Reader::ReadRecord(Slice* record, std::string* scratch)` local variable `in_fragmented_record` in switch case `kFullType` block is assigned to false and then does `return` without use. In the other switch case `kFirstType` block the same `in_fragmented_record` is assigned to false, but later assigned to true without prior use. Removed assignment for both cases.
scan-build reprots:
http://home.fburl.com/~sugak/latest20/report-bb86b0.html#EndPathhttp://home.fburl.com/~sugak/latest20/report-a975be.html#EndPath
**table/plain_table_key_coding.cc**
Local variable `user_key_size` is assigned when declared. But then in both places where it is used assigned to `static_cast<uint32_t>(key.size() - 8)`. Changed to initialize the variable to the proper value in declaration.
scan-build report:
http://home.fburl.com/~sugak/latest20/report-9e6b86.html#EndPath
**tools/db_stress.cc**
Missing `break` in switch case block. This seems to be a bug. Added missing `break`.
Test Plan:
Make sure all tests are passing and scan-build does not report 'Dead assignment' and 'Dead initialization' bugs.
```lang=bash
% make check
% make analyze
```
Reviewers: meyering, igor, kradhakrishnan, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33795
