expressions/predicate/PredicateCost.hpp

/**
 *   Copyright 2011-2015 Quickstep Technologies LLC.
 *   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_PREDICATE_PREDICATE_COST_HPP_
#define QUICKSTEP_EXPRESSIONS_PREDICATE_PREDICATE_COST_HPP_

#include <cstdint>
#include <limits>

namespace quickstep {

/**
 * @brief Represents a simple estimation of the cost to evaluate a
 *        ComparisonPredicate using a particular sub-block.
 **/
typedef std::uint8_t predicate_cost_t;

namespace predicate_cost {

// TODO(chasseur): For now, these static constants define an order of
// preference for different predicate-evaluation methods. In the future, we may
// want to use statistics to get more accurate cost estimation.
static constexpr predicate_cost_t kConstantTime = 0;
static constexpr predicate_cost_t kBinarySearch = 1;
static constexpr predicate_cost_t kTreeSearch = 2;
static constexpr predicate_cost_t kCompressedColumnScan = 3;
static constexpr predicate_cost_t kColumnScan = 4;
static constexpr predicate_cost_t kCompressedRowScan = 5;
static constexpr predicate_cost_t kRowScan = 6;
static constexpr predicate_cost_t kInfinite = std::numeric_limits<predicate_cost_t>::max();

}  // namespace predicate_cost

/**
 * @brief Determine if a predicate_cost_t represents a simple scan on a
 *        TupleStorageSubBlock.
 **/
inline bool PredicateCostIsSimpleScan(const predicate_cost_t cost) {
  return (cost == predicate_cost::kRowScan) || (cost == predicate_cost::kColumnScan);
}

}  // namespace quickstep

#endif  // QUICKSTEP_EXPRESSIONS_PREDICATE_PREDICATE_COST_HPP_