thirdparty/rocksdb/utilities/cassandra/cassandra_compaction_filter.h

// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).

#pragma once
#include <string>
#include "rocksdb/compaction_filter.h"
#include "rocksdb/slice.h"

namespace rocksdb {
namespace cassandra {

/**
 * Compaction filter for removing expired Cassandra data with ttl.
 * If option `purge_ttl_on_expiration` is set to true, expired data
 * will be directly purged. Otherwise expired data will be converted
 * tombstones first, then be eventally removed after gc grace period. 
 * `purge_ttl_on_expiration` should only be on in the case all the 
 * writes have same ttl setting, otherwise it could bring old data back.
 */
class CassandraCompactionFilter : public CompactionFilter {
public:
  explicit CassandraCompactionFilter(bool purge_ttl_on_expiration)
    : purge_ttl_on_expiration_(purge_ttl_on_expiration) {}

  const char* Name() const override;
  virtual Decision FilterV2(int level,
                            const Slice& key,
                            ValueType value_type,
                            const Slice& existing_value,
                            std::string* new_value,
                            std::string* skip_until) const override;

private:
  bool purge_ttl_on_expiration_;
};
}  // namespace cassandra
}  // namespace rocksdb