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.beam.sdk.extensions.sql.impl.rel;
  
  import java.util.List;
  import org.apache.beam.sdk.extensions.sql.impl.planner.BeamCostModel;
  import org.apache.beam.sdk.extensions.sql.impl.planner.BeamRelMetadataQuery;
  import org.apache.beam.sdk.extensions.sql.impl.planner.NodeStats;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.transforms.windowing.WindowFn;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PCollectionList;
  import org.apache.beam.sdk.values.Row;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.plan.RelOptCluster;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.plan.RelOptPlanner;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.plan.RelTraitSet;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.RelNode;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.core.SetOp;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.core.Union;
  
  /**
   * {@link BeamRelNode} to replace a {@link Union}.
   *
   * <p>{@code BeamUnionRel} needs the input of it have the same {@link WindowFn}. From the SQL
   * perspective, two cases are supported:
   *
   * <p>1) Do not use {@code grouped window function}:
   *
   * <pre>{@code
   * select * from person UNION select * from person
   * }</pre>
   *
   * <p>2) Use the same {@code grouped window function}, with the same param:
   *
   * <pre>{@code
   * select id, count(*) from person
   * group by id, TUMBLE(order_time, INTERVAL '1' HOUR)
   * UNION
   * select * from person
   * group by id, TUMBLE(order_time, INTERVAL '1' HOUR)
   * }</pre>
   *
   * <p>Inputs with different group functions are NOT supported:
   *
   * <pre>{@code
   * select id, count(*) from person
   * group by id, TUMBLE(order_time, INTERVAL '1' HOUR)
   * UNION
   * select * from person
   * group by id, TUMBLE(order_time, INTERVAL '2' HOUR)
   * }</pre>
   */
  public class BeamUnionRel extends Union implements BeamRelNode {
    public BeamUnionRel(
        RelOptCluster cluster, RelTraitSet traits, List<RelNode> inputs, boolean all) {
      super(cluster, traits, inputs, all);
    }
  
    @Override
    public SetOp copy(RelTraitSet traitSet, List<RelNode> inputs, boolean all) {
      return new BeamUnionRel(getCluster(), traitSet, inputs, all);
    }
  
    @Override
    public PTransform<PCollectionList<Row>, PCollection<Row>> buildPTransform() {
      return new BeamSetOperatorRelBase(this, BeamSetOperatorRelBase.OpType.UNION, all);
    }
  
    @Override
    public NodeStats estimateNodeStats(BeamRelMetadataQuery mq) {
      // The summation of the input stats
      NodeStats summationOfEstimates =
          inputs.stream()
              .map(input -> BeamSqlRelUtils.getNodeStats(input, mq))
              .reduce(NodeStats.create(0, 0, 0), NodeStats::plus);
      // If all is set then we propagate duplicated values. Otherwise we assume a constant factor of
      // them are duplicate.
      summationOfEstimates = all ? summationOfEstimates : summationOfEstimates.multiply(0.5);
      return summationOfEstimates;
    }
  
    @Override
    public BeamCostModel beamComputeSelfCost(RelOptPlanner planner, BeamRelMetadataQuery mq) {
      NodeStats summationOfEstimates =
          inputs.stream()
              .map(input -> BeamSqlRelUtils.getNodeStats(input, mq))
              .reduce(NodeStats.create(0, 0, 0), NodeStats::plus);
  
      return BeamCostModel.FACTORY.makeCost(
          summationOfEstimates.getRowCount(), summationOfEstimates.getRate());
    }
  }
  