add db_test for changing memtable size

Summary:
The test only covers changing write_buffer_size. Other changable
parameters such bloom bits/probes are not obvious how to test.
Suggestions are welcome

Test Plan: db_test

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D24429
Log RocksDB version

Summary: This will be much easier than reviewing git sha's we currently have in our LOGs

Test Plan: none

Reviewers: sdong, yhchiang, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D24591
RocksJava Makefile includes incorrect paths to version.h
Merge pull request #342 from fyrz/java_makefile_fix

RocksJava Makefile includes incorrect paths to version.h
SkipListRep::LookaheadIterator

Summary:
This diff introduces the `lookahead` argument to `SkipListFactory()`. This is an
optimization for the tailing use case which includes many seeks. E.g. consider
the following operations on a skip list iterator:

   Seek(x), Next(), Next(), Seek(x+2), Next(), Seek(x+3), Next(), Next(), ...

If `lookahead` is positive, `SkipListRep` will return an iterator which also
keeps track of the previously visited node. Seek() then first does a linear
search starting from that node (up to `lookahead` steps). As in the tailing
example above, this may require fewer than ~log(n) comparisons as with regular
skip list search.

Test Plan:
Added a new benchmark (`fillseekseq`) which simulates the usage pattern. It
first writes N records (with consecutive keys), then measures how much time it
takes to read them by calling `Seek()` and `Next()`.

   $ time ./db_bench -num 10000000 -benchmarks fillseekseq -prefix_size 1 \
      -key_size 8 -write_buffer_size $[1024*1024*1024] -value_size 50 \
      -seekseq_next 2 -skip_list_lookahead=0
   [...]
   DB path: [/dev/shm/rocksdbtest/dbbench]
   fillseekseq  :       0.389 micros/op 2569047 ops/sec;

   real    0m21.806s
   user    0m12.106s
   sys     0m9.672s

   $ time ./db_bench [...] -skip_list_lookahead=2
   [...]
   DB path: [/dev/shm/rocksdbtest/dbbench]
   fillseekseq  :       0.153 micros/op 6540684 ops/sec;

   real    0m19.469s
   user    0m10.192s
   sys     0m9.252s

Reviewers: ljin, sdong, igor

Reviewed By: igor

Subscribers: dhruba, leveldb, march, lovro

Differential Revision: https://reviews.facebook.net/D23997
Update HISTORY for 3.6
RocksJava should support not only BlockBased Bloomfilter
Improved JavaDoc
Merge pull request #339 from fyrz/bloomFilterSupportNewFormat

RocksJava should support not only BlockBased Bloomfilter
db_bench: set thread pool size according to max_background_flushes

Summary: option max_background_flushes doesn't make sense if thread pool size is not set accordingly. Set the thread pool size as what we do for max_background_compactions.

Test Plan: Run db_bench with max_background_flushes > 1

Reviewers: yhchiang, igor, rven, ljin

Reviewed By: ljin

Subscribers: MarkCallaghan, leveldb

Differential Revision: https://reviews.facebook.net/D24717
minor update to benchmark script

Summary: Try to match some parameters from Dhruba's benchmarks on github

Test Plan: ran it

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D24687
convert Options from string

Summary: Allow accepting Options as a string of key/value pairs

Test Plan: unit test

Reviewers: yhchiang, sdong, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D24597
Fixed compile error on Mac: default arguments for lambda expressions

Summary:
Fixed the following compile error on Mac.

db/db_test.cc:8618:52: error: C++11 forbids default arguments for lambda expressions [-Werror,-Wlambda-extensions]
  auto gen_l0_kb = [this](int start, int size, int stride = 1) {
                                                   ^        ~
1 error generated.

Test Plan:
db_test
Fixed Mac compile error in util/options_test.cc

Summary:
Fixed the following error in Mac:

./util/testharness.h:93:19: error: comparison of integers of different signs: 'const unsigned long' and 'const int' [-Werror,-Wsign-compare]
  BINARY_OP(IsEq, ==)
  ~~~~~~~~~~~~~~~~^~~
./util/testharness.h:86:14: note: expanded from macro 'BINARY_OP'
    if (! (x op y)) {                                   \
             ^
util/options_test.cc:269:3: note: in instantiation of function template specialization 'rocksdb::test::Tester::IsEq<unsigned long, int>' requested here
  ASSERT_EQ(new_cf_opt.write_buffer_size, 5);
  ^

Test Plan:
options_test
WriteBatchWithIndex to support an option to overwrite rows when operating the same key

Summary: With a new option, when accepting a new key, WriteBatchWithIndex will find an existing index of the same key, and replace the content of it.

Test Plan: Add a unit test case.

Reviewers: ljin, yhchiang, rven, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D24753
WriteBatchWithIndex's iterator to support SeekToFirst(), SeekToLast() and Prev()

Summary: Support SeekToFirst(), SeekToLast() and Prev() in WBWIIterator, returned by WriteBatchWithIndex::NewIterator().

Test Plan: Write unit test cases to cover the case.

Reviewers: ljin, igor

Reviewed By: igor

Subscribers: rven, yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D24765
WriteBatchWithIndex supports an iterator that merge its change with a base iterator.

Summary: Add an iterator that combines base_iterator of type Iterator* with delta iterator of type WBWIIterator*.

Test Plan: nothing yet. work in progress

Reviewers: ljin, igor

Reviewed By: igor

Subscribers: rven, yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D24741
JavaDoc improvements on RocksJava

Added some more documentation improvements and readability
improvements.
Minor adjustment to prevent two warnings
32-Bit RocksJava resolution for jlong overflows

Summary:
This pull request solves the jlong overflow problem on 32-Bit machines as described in https://github.com/facebook/rocksdb/issues/278:

1. There is a new org.rocksdb.test.PlatformRandomHelper to assist in getting random values. For 32 Bit the getLong method is overriden by xpromaches code above. For 64 Bit it behaves as is.
2. The detection should be cross-platform (Windows is supported though it is not ported completely yet).
3. Every JNI method which sets jlong values must check if the value fits into size_t. If it overflows size_t a InvalidArgument Status object will be returned. If its ok a OK Status will be returned.
4. Setters which have this check will throw a RocksDBException if its no OK Status.

Additionally some other parts of code were corrected using the wrong type casts.

Test Plan:
make rocksdbjava
make jtest

Differential Revision: https://reviews.facebook.net/D24531