RocksDB - WriteBatchWithIndex BaseIterator example

simple_example.cc

// Copyright (c) 2013, 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.
#include <cstdio>
#include <string>
#include <iostream>

#include "rocksdb/db.h"
#include "rocksdb/slice.h"
#include "rocksdb/options.h"
#include "rocksdb/utilities/write_batch_with_index.h"
using namespace rocksdb;

std::string kDBPath = "/tmp/rocksdb_simple_example";

int main() {
  DB* db;
  Options options;
  // Optimize RocksDB. This is the easiest way to get RocksDB to perform well
  options.IncreaseParallelism();
  options.OptimizeLevelStyleCompaction();
  // create the DB if it's not already present
  options.create_if_missing = true;

  // open DB
  Status s = DB::Open(options, kDBPath, &db);
  assert(s.ok());

  // Put key-value
  s = db->Put(WriteOptions(), "key", "value");
  assert(s.ok());
  s = db->Put(WriteOptions(), "key2", "value");
  assert(s.ok());

  std::string value;
  // get value
  s = db->Get(ReadOptions(), "key", &value);
  assert(s.ok());
  assert(value == "value");

  ColumnFamilyHandle* handle = db->DefaultColumnFamily();
  WriteBatchWithIndex* wbi = new WriteBatchWithIndex(BytewiseComparator(), 0, true);
  wbi->Put("key", "valueV2");

  Iterator* iter = db->NewIterator(ReadOptions());
  Iterator* wbi_iter = wbi->NewIteratorWithBase(handle, iter);

  wbi_iter->SeekToFirst();
  std::cout << "Value for key: " << wbi_iter->key().ToString() << "\tis: " << wbi_iter->value().ToString() << std::endl;
  wbi_iter->Next();
  std::cout << "Value for key: " << wbi_iter->key().ToString() << "\tis: " << wbi_iter->value().ToString() << std::endl;

  delete db;
  return 0;
}