[Java] Enable filluniquerandom, readseq, BloomFilter, and 70+ command-line options to DbBenchmark.java

Summary:
* Add filluniquerandom
* Add readseq, implemented using iterator.
* Realize most command-line-arguments from db_bench.cc (70+).
* Some code are commented out as some of the options in Options
  not yet have Java bindings.
* Add default option to DbBenchmark.
* RocksDB will now take the ownership of all c++ raw-pointers from Options, which includes a c++ raw-pointer for Filter.

Test Plan: ./jdb_bench.sh --db=/tmp/rocksjava-bench/db --num_levels=6 --key_size=20 --prefix_size=20 --keys_per_prefix=0 --value_size=100 --block_size=4096 --cache_size=17179869184 --cache_numshardbits=6 --compression_ratio=1 --min_level_to_compress=-1 --disable_seek_compaction=1 --hard_rate_limit=2 --write_buffer_size=134217728 --max_write_buffer_number=2 --level0_file_num_compaction_trigger=8 --target_file_size_base=134217728 --max_bytes_for_level_base=1073741824 --disable_wal=0 --wal_dir=/tmp/rocksjava-bench/wal --sync=0 --disable_data_sync=1 --verify_checksum=1 --delete_obsolete_files_period_micros=314572800 --max_grandparent_overlap_factor=10 --max_background_compactions=4 --max_background_flushes=0 --level0_slowdown_writes_trigger=16 --level0_stop_writes_trigger=24 --statistics=0 --stats_per_interval=0 --stats_interval=1048576 --histogram=0 --use_plain_table=1 --open_files=-1 --mmap_read=1 --mmap_write=0 --memtablerep=prefix_hash --bloom_bits=10 --bloom_locality=1 --perf_level=0 --benchmarks=filluniquerandom,readseq,readrandom --use_existing_db=0 --threads=4

Reviewers: haobo, dhruba, sdong, ankgup87, rsumbaly, swapnilghike, zzbennett

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18267

java/org/rocksdb/RocksDB.java

@@ -36,6 +36,7 @@ public class RocksDB {
     // the c++ one.
     Options options = new Options();
     db.open(options.nativeHandle_, options.cacheSize_, path);
+    db.transferCppRawPointersOwnership(options);
     options.dispose();
     return db;
   }
@@ -46,8 +47,12 @@ public class RocksDB {
    */
   public static RocksDB open(Options options, String path)
       throws RocksDBException {
+    // when non-default Options is used, keeping an Options reference
+    // in RocksDB can prevent Java to GC during the life-time of
+    // the currently-created RocksDB.
     RocksDB db = new RocksDB();
     db.open(options.nativeHandle_, options.cacheSize_, path);
+    db.transferCppRawPointersOwnershipFrom(options);
     return db;
   }
 
@@ -195,6 +200,17 @@ public class RocksDB {
     nativeHandle_ = 0;
   }
 
+  /**
+   * Transfer the ownership of all c++ raw-pointers from Options
+   * to RocksDB to ensure the life-time of those raw-pointers
+   * will be at least as long as the life-time of any RocksDB
+   * that uses these raw-pointers.
+   */
+  protected void transferCppRawPointersOwnershipFrom(Options opt) {
+    filter_ = opt.filter_;
+    opt.filter_ = null;
+  }
+
   // native methods
   protected native void open(
       long optionsHandle, long cacheSize, String path) throws RocksDBException;
@@ -227,4 +243,5 @@ public class RocksDB {
   protected native void close0();
 
   protected long nativeHandle_;
+  protected Filter filter_;
 }