JoinFilterPushDown.h

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/*
 * Copyright 2022 HEAVY.AI, 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.
 */

#pragma once

#include <cstddef>
#include <numeric>

#include "QueryEngine/InputMetadata.h"
#include "QueryEngine/RangeTableIndexVisitor.h"

extern bool g_enable_filter_push_down;
extern float g_filter_push_down_low_frac;
extern float g_filter_push_down_high_frac;
extern size_t g_filter_push_down_passing_row_ubound;

struct PushedDownFilterInfo {
  std::vector<std::shared_ptr<Analyzer::Expr>> filter_expressions;
  size_t input_prev;
  size_t input_start;
  size_t input_next;
};

struct FilterSelectivity {
  const bool is_valid;
  const float fraction_passing;
  const size_t total_rows_upper_bound;

  size_t getRowsPassingUpperBound() const {
    return fraction_passing * total_rows_upper_bound;
  }
  bool isFilterSelectiveEnough() const {
    auto low_frac_threshold = (g_filter_push_down_low_frac >= 0.0)
                                  ? std::min(g_filter_push_down_low_frac, 1.0f)
                                  : kFractionPassingLowThreshold;
    auto high_frac_threshold = (g_filter_push_down_high_frac >= 0.0)
                                   ? std::min(g_filter_push_down_high_frac, 1.0f)
                                   : kFractionPassingHighThreshold;
    auto rows_ubound_threshold = (g_filter_push_down_passing_row_ubound > 0)
                                     ? g_filter_push_down_passing_row_ubound
                                     : kRowsPassingUpperBoundThreshold;
    return (fraction_passing < low_frac_threshold ||
            (fraction_passing < high_frac_threshold &&
             getRowsPassingUpperBound() < rows_ubound_threshold));
  }

  static constexpr float kFractionPassingLowThreshold = 0.1;
  static constexpr float kFractionPassingHighThreshold = 0.5;
  static constexpr size_t kRowsPassingUpperBoundThreshold = 4000000;
};

bool to_gather_info_for_filter_selectivity(
    const std::vector<InputTableInfo>& table_infos);

std::vector<PushedDownFilterInfo> find_push_down_filters(
    const RelAlgExecutionUnit& ra_exe_unit,
    const std::vector<size_t>& input_permutation,
    const std::vector<size_t>& left_deep_join_input_sizes);