Remove port::MemoryBarrier() from table_reader_bench

Summary: port::MemoryBarrier() is not recommended to use outside of port. Remove it.

Test Plan: run table_reader_bench

Reviewers: ljin, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21075
Implementing CuckooTableReader::NewIterator

Summary:
- Reads key-value pairs from file and builds an in-memory index of key-to-bucket id map in sorted order of key.
- Assumes bytewise comparator for sorting keys.
- Test changes

Test Plan:
cuckoo_table_reader_test --enable_perf
valgrind_check
asan_check

Reviewers: yhchiang, sdong, ljin

Reviewed By: ljin

Subscribers: leveldb, igor

Differential Revision: https://reviews.facebook.net/D20721
Changing implementaiton of CuckooTableBuilder to not take file_size, key_length, value_length.

Summary:
 - Maintain a list of key-value pairs as vectors during Add operation.
 - Start building hash table only when Finish() is called.
 - This approach takes more time and space but avoids taking file_size, key and value lengths.
 - Rewrote cuckoo_table_builder_test

I did not know about IterKey while writing this diff. I shall change places where IterKey could be used instead of std::string tomorrow. Please review rest of the logic.

Test Plan:
cuckoo_table_reader_test --enable_perf
cuckoo_table_builder_test
valgrind_check
asan_check

Reviewers: sdong, igor, yhchiang, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D20907
Add DB property "rocksdb.estimate-table-readers-mem"

Summary:
Add a DB Property "rocksdb.estimate-table-readers-mem" to return estimated memory usage by all loaded table readers, other than allocated from block cache.

Refactor the property codes to allow getting property from a version, with DB mutex not acquired.

Test Plan: Add several checks of this new property in existing codes for various cases.

Reviewers: yhchiang, ljin

Reviewed By: ljin

Subscribers: xjin, igor, leveldb

Differential Revision: https://reviews.facebook.net/D20733
Add support for C bindings to the compaction V2 filter mechanism.

Test Plan: make c_test && ./c_test

Some fixes after merge.
Fix typo, add missing inclusion of state void* in invocation of
create_compaction_filter_v2_.
Fix valgrind failure caused by recent checked-in.

Summary: Initialize un-initialized parameters

Test Plan: run the failed test (c_test)

Reviewers: yhchiang, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21249
Minor: fix a format

Summary: A format fixing

Test Plan: N/A

Reviewers: ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21255
fix various 'comparison of integers of different signs' compiling errors under macosx
Merge pull request #226 from bbiao/master

fix various 'comparison of integers of different signs' compiling errors...
Merge pull request #224 from cockroachdb/spencerkimball/compaction-filter-v2-c-bindings

Add support for C bindings to the compaction V2 filter mechanism.
Fix c_test
Fix leak in c_test
Fix db_test and DBIter

Summary: Fix old issue with DBTest.Randomized with BlockBasedTableWithWholeKeyHashIndex + added printing in DBTest.Randomized.

Test Plan: make all check

Reviewers: zagfox, igor, ljin, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21003
Fix SIGSEGV in travis

Summary:
Travis build was failing a lot. For example see https://travis-ci.org/facebook/rocksdb/builds/31425845

This fixes it.

Also, please don't put any code after SignalAll :)

Test Plan: no more SIGSEGV

Reviewers: yhchiang, sdong, ljin

Reviewed By: ljin

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D21417
Need to schedule compactions when manual compaction finishes

Summary: If there is an outstanding compaction scheduled but at the time a manual compaction is triggered, the manual compaction will preempt. In the end of the manual compaction, we should try to schedule compactions to make sure those preempted ones are not skipped.

Test Plan: make all check

Reviewers: yhchiang, ljin

Reviewed By: ljin

Subscribers: leveldb, dhruba, igor

Differential Revision: https://reviews.facebook.net/D21321
Include candidate files under options.db_log_dir in FindObsoleteFiles()

Summary: In FindObsoleteFiles(), we don't scan db_log_dir. Add it.

Test Plan: make all check

Reviewers: ljin, igor, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb, yhchiang

Differential Revision: https://reviews.facebook.net/D21429
Changes to support unity build:
* Script for building the unity.cc file via Makefile
* Unity executable Makefile target for testing builds
* Source code changes to fix compilation of unity build