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;
  import org.apache.calcite.plan.RelRule;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Aggregate;
  import org.apache.calcite.rel.core.AggregateCall;
  import org.apache.calcite.rel.core.Join;
  import org.apache.calcite.rel.core.JoinRelType;
  import org.apache.calcite.rel.logical.LogicalAggregate;
  import org.apache.calcite.rel.logical.LogicalJoin;
  import org.apache.calcite.rex.RexNode;
  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 org.apache.calcite.util.mapping.Mappings;
  
  import com.google.common.collect.ImmutableList;
  
  import org.immutables.value.Value;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * Planner rule that matches an {@link org.apache.calcite.rel.core.Aggregate}
   * on a {@link org.apache.calcite.rel.core.Join} and removes the left input
   * of the join provided that the left input is also a left join if possible.
   *
   * <p>For instance,
   *
   * <blockquote>
   * <pre>select distinct s.product_id, pc.product_id
   * from sales as s
   * left join product as p
   *   on s.product_id = p.product_id
   * left join product_class pc
   *   on s.product_id = pc.product_id</pre></blockquote>
   *
   * <p>becomes
   *
   * <blockquote>
   * <pre>select distinct s.product_id, pc.product_id
   * from sales as s
   * left join product_class pc
   *   on s.product_id = pc.product_id</pre></blockquote>
   *
   * @see CoreRules#AGGREGATE_JOIN_JOIN_REMOVE
   */
  @Value.Enclosing
  public class AggregateJoinJoinRemoveRule
      extends RelRule<AggregateJoinJoinRemoveRule.Config>
      implements TransformationRule {
  
    /** Creates an AggregateJoinJoinRemoveRule. */
    protected AggregateJoinJoinRemoveRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public AggregateJoinJoinRemoveRule(
        Class<? extends Aggregate> aggregateClass,
        Class<? extends Join> joinClass, RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT
          .withRelBuilderFactory(relBuilderFactory)
          .as(Config.class)
          .withOperandFor(aggregateClass, joinClass));
    }
  
    @Override public void onMatch(RelOptRuleCall call) {
      final Aggregate aggregate = call.rel(0);
      final Join topJoin = call.rel(1);
      final Join bottomJoin = call.rel(2);
      int leftBottomChildSize = bottomJoin.getLeft().getRowType()
          .getFieldCount();
  
      // Check whether the aggregate uses columns in the right input of
      // bottom join.
      final Set<Integer> allFields = RelOptUtil.getAllFields(aggregate);
      if (allFields.stream().anyMatch(i -> i >= leftBottomChildSize
          && i < bottomJoin.getRowType().getFieldCount())) {
        return;
      }
  
      if (aggregate.getAggCallList().stream().anyMatch(aggregateCall ->
          !aggregateCall.isDistinct())) {
        return;
      }
  
      // Check whether the top join uses columns in the right input of bottom join.
      final List<Integer> leftKeys = new ArrayList<>();
      RelOptUtil.splitJoinCondition(topJoin.getLeft(), topJoin.getRight(),
          topJoin.getCondition(), leftKeys, new ArrayList<>(),
          new ArrayList<>());
      if (leftKeys.stream().anyMatch(s -> s >= leftBottomChildSize)) {
        return;
      }
  
      // Check whether left join keys in top join and bottom join are equal.
      final List<Integer> leftChildKeys = new ArrayList<>();
      RelOptUtil.splitJoinCondition(bottomJoin.getLeft(), bottomJoin.getRight(),
          bottomJoin.getCondition(), leftChildKeys, new ArrayList<>(),
          new ArrayList<>());
      if (!leftKeys.equals(leftChildKeys)) {
        return;
      }
  
      int offset = bottomJoin.getRight().getRowType().getFieldCount();
      final RelBuilder relBuilder = call.builder();
      RexNode condition =
          RexUtil.shift(topJoin.getCondition(), leftBottomChildSize, -offset);
      RelNode join = relBuilder.push(bottomJoin.getLeft())
          .push(topJoin.getRight())
          .join(topJoin.getJoinType(), condition)
          .build();
  
      final Map<Integer, Integer> map = new HashMap<>();
      allFields.forEach(
          index ->
              map.put(index,
                  index < leftBottomChildSize ? index : index - offset));
      final ImmutableBitSet groupSet = aggregate.getGroupSet().permute(map);
  
      final ImmutableList.Builder<AggregateCall> aggCalls =
          ImmutableList.builder();
      final int sourceCount = aggregate.getInput().getRowType().getFieldCount();
      final Mappings.TargetMapping targetMapping =
          Mappings.target(map, sourceCount, sourceCount);
      aggregate.getAggCallList().forEach(
          aggregateCall ->
              aggCalls.add(aggregateCall.transform(targetMapping)));
  
      RelNode newAggregate = relBuilder.push(join)
          .aggregate(relBuilder.groupKey(groupSet), aggCalls.build())
          .build();
  
      call.transformTo(newAggregate);
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableAggregateJoinJoinRemoveRule.Config.of()
          .withOperandFor(LogicalAggregate.class, LogicalJoin.class);
  
      @Override default AggregateJoinJoinRemoveRule toRule() {
        return new AggregateJoinJoinRemoveRule(this);
      }
  
      /** Defines an operand tree for the given classes. */
      default Config withOperandFor(Class<? extends Aggregate> aggregateClass,
          Class<? extends Join> joinClass) {
        return withOperandSupplier(b0 -> b0.operand(aggregateClass)
            .oneInput(b1 -> b1.operand(joinClass)
                .predicate(join -> join.getJoinType() == JoinRelType.LEFT)
                .inputs(b2 -> b2.operand(joinClass)
                    .predicate(join -> join.getJoinType() == JoinRelType.LEFT)
                    .anyInputs()))).as(Config.class);
      }
    }
  }
  