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.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.HashMap;
  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 join
   * provided that the join is a left join or right join and it computes no
   * aggregate functions or all the aggregate calls have distinct.
   *
   * <p>For instance,
   *
   * <blockquote>
   * <pre>select distinct s.product_id from
   * sales as s
   * left join product as p
   * on s.product_id = p.product_id</pre></blockquote>
   *
   * <p>becomes
   *
   * <blockquote>
   * <pre>select distinct s.product_id from sales as s</pre></blockquote>
   *
   * @see CoreRules#AGGREGATE_JOIN_REMOVE
   */
  @Value.Enclosing
  public class AggregateJoinRemoveRule
      extends RelRule<AggregateJoinRemoveRule.Config>
      implements TransformationRule {
  
    /** Creates an AggregateJoinRemoveRule. */
    protected AggregateJoinRemoveRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public AggregateJoinRemoveRule(
        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 join = call.rel(1);
      boolean isLeftJoin = join.getJoinType() == JoinRelType.LEFT;
      int lower = isLeftJoin
          ? join.getLeft().getRowType().getFieldCount() : 0;
      int upper =
          isLeftJoin ? join.getRowType().getFieldCount()
              : join.getLeft().getRowType().getFieldCount();
  
      // Check whether the aggregate uses columns whose index is between
      // lower(included) and upper(excluded).
      final Set<Integer> allFields = RelOptUtil.getAllFields(aggregate);
      if (allFields.stream().anyMatch(i -> i >= lower && i < upper)) {
        return;
      }
  
      if (aggregate.getAggCallList().stream().anyMatch(
          aggregateCall -> !aggregateCall.isDistinct())) {
        return;
      }
  
      RelNode node;
      if (isLeftJoin) {
        node =
            aggregate.copy(aggregate.getTraitSet(), join.getLeft(),
                aggregate.getGroupSet(), aggregate.getGroupSets(),
                aggregate.getAggCallList());
      } else {
        final Map<Integer, Integer> map = new HashMap<>();
        allFields.forEach(index -> map.put(index, index - upper));
        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)));
  
        final RelBuilder relBuilder = call.builder();
        node = relBuilder.push(join.getRight())
            .aggregate(relBuilder.groupKey(groupSet), aggCalls.build())
            .build();
      }
      call.transformTo(node);
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableAggregateJoinRemoveRule.Config.of()
          .withOperandFor(LogicalAggregate.class, LogicalJoin.class);
  
      @Override default AggregateJoinRemoveRule toRule() {
        return new AggregateJoinRemoveRule(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
                            || join.getJoinType() == JoinRelType.RIGHT)
                    .anyInputs()))
            .as(Config.class);
      }
    }
  }
  