query_optimizer/rules/RuleHelper.cpp

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 **/

#include <vector>
#include <unordered_map>

#include "query_optimizer/expressions/Alias.hpp"
#include "query_optimizer/expressions/AttributeReference.hpp"
#include "query_optimizer/expressions/ExprId.hpp"
#include "query_optimizer/expressions/Expression.hpp"
#include "query_optimizer/expressions/LogicalAnd.hpp"
#include "query_optimizer/expressions/NamedExpression.hpp"
#include "query_optimizer/expressions/PatternMatcher.hpp"
#include "query_optimizer/rules/UpdateExpression.hpp"

namespace quickstep {
namespace optimizer {

namespace E = ::quickstep::optimizer::expressions;

std::vector<expressions::PredicatePtr> GetConjunctivePredicates(
    const expressions::PredicatePtr &predicate) {
  expressions::LogicalAndPtr logical_and;
  if (expressions::SomeLogicalAnd::MatchesWithConditionalCast(predicate, &logical_and)) {
    return logical_and->operands();
  } else {
    return {predicate};
  }
}

void PullUpProjectExpressions(
    const std::vector<E::NamedExpressionPtr> &project_expressions_for_pullup,
    const std::vector<std::vector<E::ExpressionPtr>*> &non_project_expression_lists,
    const std::vector<std::vector<E::NamedExpressionPtr>*> &project_expression_lists) {
  std::unordered_map<E::ExprId, E::ExpressionPtr> expression_replacement_map;
  for (const E::NamedExpressionPtr &named_expression :
       project_expressions_for_pullup) {
    E::AliasPtr alias;
    if (E::SomeAlias::MatchesWithConditionalCast(named_expression, &alias)) {
      const E::ExpressionPtr replacement_expression = alias->expression();
      expression_replacement_map.emplace(alias->id(), replacement_expression);
    }
  }

  if (!expression_replacement_map.empty()) {
    UpdateExpression rule(expression_replacement_map);

    // For non-project expressions, simply apply the UpdateExpression rule.
    for (std::vector<E::ExpressionPtr> *non_project_expressions :
         non_project_expression_lists) {
      for (std::vector<E::ExpressionPtr>::size_type i = 0; i < non_project_expressions->size(); ++i) {
        const E::ExpressionPtr &expression_to_update = (*non_project_expressions)[i];
        (*non_project_expressions)[i] = rule.apply(expression_to_update);
      }
    }

    for (std::vector<E::NamedExpressionPtr> *project_expressions :
         project_expression_lists) {
      for (std::vector<E::NamedExpressionPtr>::size_type i = 0; i < project_expressions->size(); ++i) {
        const E::NamedExpressionPtr &expression_to_update = (*project_expressions)[i];
        E::ExpressionPtr updated_expression = rule.apply(expression_to_update);

        E::NamedExpressionPtr updated_named_expression;
        if (E::SomeNamedExpression::MatchesWithConditionalCast(updated_expression,
                                                               &updated_named_expression) &&
            expression_to_update->id() == updated_named_expression->id() &&
            expression_to_update->attribute_alias() == updated_named_expression->attribute_alias()) {
          // Pull up directly if the updated expression has the same ExprId and
          // attribute_alias as the original project expression.
          (*project_expressions)[i] = updated_named_expression;
        } else {
          // Otherwise create an Alias to wrap the updated expression.
          (*project_expressions)[i] =
              E::Alias::Create(expression_to_update->id(),
                               updated_expression,
                               expression_to_update->attribute_name(),
                               expression_to_update->attribute_alias(),
                               expression_to_update->relation_name());
        }
      }
    }
  }
}

}  // namespace optimizer
}  // namespace quickstep