content: /*
   * 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.
   */
  package org.apache.calcite.rel.rules;
  
  import org.apache.calcite.plan.RelOptRuleCall;
  import org.apache.calcite.plan.RelOptUtil.Exists;
  import org.apache.calcite.plan.RelRule;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.CorrelationId;
  import org.apache.calcite.rel.core.Intersect;
  import org.apache.calcite.rel.logical.LogicalIntersect;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeField;
  import org.apache.calcite.rex.RexBuilder;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.rex.RexSubQuery;
  import org.apache.calcite.rex.RexUtil;
  import org.apache.calcite.tools.RelBuilder;
  import org.apache.calcite.tools.RelBuilderFactory;
  import org.apache.calcite.util.ImmutableBitSet;
  
  import com.google.common.collect.ImmutableSet;
  
  import org.immutables.value.Value;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.stream.Collectors;
  
  /**
   * Planner rule that translates a {@link Intersect}
   * (<code>all</code> = <code>false</code>)
   * into a {@link Exists}.
   *
   * @see CoreRules#INTERSECT_TO_EXISTS
   */
  @Value.Enclosing
  public class IntersectToExistsRule
      extends RelRule<IntersectToExistsRule.Config>
      implements TransformationRule {
  
    /** Creates an IntersectToExistRule. */
    protected IntersectToExistsRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public IntersectToExistsRule(Class<? extends Intersect> intersectClass,
        RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
          .as(Config.class)
          .withOperandFor(intersectClass));
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void onMatch(RelOptRuleCall call) {
      final Intersect intersect = call.rel(0);
      if (intersect.all) {
        return; // nothing we can do
      }
  
      final RelBuilder builder = call.builder();
      final RexBuilder rexBuilder = builder.getRexBuilder();
  
      RelDataType rowType = intersect.getRowType();
      List<RelNode> inputs = intersect.getInputs();
      RelNode current = inputs.get(0);
  
      // get all column indices of intersect
      ImmutableBitSet fieldIndices = ImmutableBitSet.of(rowType.getFieldList()
          .stream().map(RelDataTypeField::getIndex)
          .collect(Collectors.toList()));
  
      // iterate over the inputs and apply exists subquery
      for (int i = 1; i < inputs.size(); i++) {
        RelNode nextInput = inputs.get(i).stripped();
  
        // create correlation
        CorrelationId correlationId = intersect.getCluster().createCorrel();
        RexNode correl =
            rexBuilder.makeCorrel(rowType, correlationId);
  
        // create condition in exists filter, and use correlation
        List<RexNode> conditions = new ArrayList<>();
        for (int fieldIndex : fieldIndices) {
          RexNode outerField = rexBuilder.makeInputRef(rowType, fieldIndex);
          RexNode innerField = rexBuilder.makeFieldAccess(correl, fieldIndex);
          conditions.add(builder.isNotDistinctFrom(innerField, outerField));
        }
        RexNode condition = RexUtil.composeConjunction(rexBuilder, conditions);
  
        // build exists subquery
        RelNode existsSubQuery = builder.push(nextInput)
            .filter(condition)
            .project(builder.fields(fieldIndices))
            .build();
  
        // apply exists subquery to the current relation
        current = builder.push(current)
            .filter(ImmutableSet.of(correlationId),
                RexSubQuery.exists(existsSubQuery))
            .build();
      }
  
      builder.push(current);
      List<RexNode> projects = new ArrayList<>();
      for (int fieldIndex : fieldIndices) {
        RexNode rexNode = builder.fields().get(fieldIndex);
        RelDataType originalType =
            rowType.getFieldList().get(projects.size()).getType();
        RexNode expr;
        if (!originalType.equals(rexNode.getType())) {
          expr = rexBuilder.makeCast(originalType, rexNode, true, false);
        } else {
          expr = rexNode;
        }
        projects.add(expr);
      }
  
      RelNode result = builder.project(projects)
          .distinct()
          .build();
  
      call.transformTo(result);
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableIntersectToExistsRule.Config.of()
          .withOperandFor(LogicalIntersect.class);
  
      @Override default IntersectToExistsRule toRule() {
        return new IntersectToExistsRule(this);
      }
  
      /** Defines an operand tree for the given classes. */
      default Config withOperandFor(Class<? extends Intersect> intersectClass) {
        return withOperandSupplier(b -> b.operand(intersectClass).anyInputs())
            .as(Config.class);
      }
    }
  }
  