expressions/aggregation/AggregateFunctionCount.hpp

/**
 *   Copyright 2015 Pivotal Software, Inc.
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 **/

#ifndef QUICKSTEP_EXPRESSIONS_AGGREGATION_AGGREGATE_FUNCTION_COUNT_HPP_
#define QUICKSTEP_EXPRESSIONS_AGGREGATION_AGGREGATE_FUNCTION_COUNT_HPP_

#include <string>
#include <vector>

#include "expressions/aggregation/AggregateFunction.hpp"
#include "expressions/aggregation/AggregationID.hpp"
#include "utility/Macros.hpp"

namespace quickstep {

class AggregationHandle;
class Type;

/** \addtogroup Expressions
 *  @{
 */

/**
 * @brief AggregateFunction representing SQL COUNT.
 **/
class AggregateFunctionCount : public AggregateFunction {
 public:
  static const AggregateFunctionCount& Instance() {
    static AggregateFunctionCount instance;
    return instance;
  }

  std::string getName() const override {
    return "COUNT";
  }

  bool canApplyToTypes(
      const std::vector<const Type*> &argument_types) const override;

  const Type* resultTypeForArgumentTypes(
      const std::vector<const Type*> &argument_types) const override;

  AggregationHandle* createHandle(
      const std::vector<const Type*> &argument_types) const override;

 private:
  AggregateFunctionCount()
      : AggregateFunction(AggregationID::kCount) {
  }

  DISALLOW_COPY_AND_ASSIGN(AggregateFunctionCount);
};

/** @} */

}  // namespace quickstep

#endif  // QUICKSTEP_EXPRESSIONS_AGGREGATION_AGGREGATE_FUNCTION_COUNT_HPP_