rocksdb/java/RocksDBColumnFamilySample.java

// Copyright (c) 2014, Facebook, Inc.  All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.

import org.rocksdb.*;

import java.util.ArrayList;
import java.util.List;

public class RocksDBColumnFamilySample {
  static {
    RocksDB.loadLibrary();
  }

  public static void main(String[] args) throws RocksDBException {
    if (args.length < 1) {
      System.out.println(
          "usage: RocksDBColumnFamilySample db_path");
      return;
    }
    String db_path = args[0];

    System.out.println("RocksDBColumnFamilySample");
    RocksDB db = null;
    Options options = null;
    ColumnFamilyHandle columnFamilyHandle = null;
    WriteBatch wb = null;
    try {
      options = new Options().setCreateIfMissing(true);
      db = RocksDB.open(options, db_path);
      assert(db != null);

      // create column family
      columnFamilyHandle = db.createColumnFamily(
          new ColumnFamilyDescriptor("new_cf".getBytes(),
          new ColumnFamilyOptions()));
      assert(columnFamilyHandle != null);

    } finally {
      if (columnFamilyHandle != null) {
        columnFamilyHandle.dispose();
      }
      if (db != null) {
        db.close();
        db = null;
      }
      if (options != null) {
        options.dispose();
      }
    }

    // open DB with two column families
    List<ColumnFamilyDescriptor> columnFamilyDescriptors = new ArrayList<>();
    // have to open default column family
    columnFamilyDescriptors.add(new ColumnFamilyDescriptor(
        RocksDB.DEFAULT_COLUMN_FAMILY, new ColumnFamilyOptions()));
    // open the new one, too
    columnFamilyDescriptors.add(new ColumnFamilyDescriptor(
        "new_cf".getBytes(), new ColumnFamilyOptions()));
    List<ColumnFamilyHandle> columnFamilyHandles = new ArrayList<>();
    try {
      db = RocksDB.open(new DBOptions(), db_path,
          columnFamilyDescriptors, columnFamilyHandles);
      assert(db != null);

      // put and get from non-default column family
      db.put(columnFamilyHandles.get(0), new WriteOptions(),
          "key".getBytes(), "value".getBytes());
      String value = new String(db.get(columnFamilyHandles.get(0),
          "key".getBytes()));

      // atomic write
      wb = new WriteBatch();
      wb.put(columnFamilyHandles.get(0), "key2".getBytes(), "value2".getBytes());
      wb.put(columnFamilyHandles.get(1), "key3".getBytes(), "value3".getBytes());
      wb.remove(columnFamilyHandles.get(0), "key".getBytes());
      db.write(new WriteOptions(), wb);

      // drop column family
      db.dropColumnFamily(columnFamilyHandles.get(1));

    } finally {
      for (ColumnFamilyHandle handle : columnFamilyHandles){
        handle.dispose();
      }
      if (db != null) {
        db.close();
      }
      if (wb != null) {
        wb.dispose();
      }
    }
  }
}