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.planner;
  
  import static org.apache.beam.sdk.util.Preconditions.checkArgumentNotNull;
  
  import java.util.List;
  import java.util.stream.Collectors;
  import org.apache.beam.sdk.extensions.sql.impl.rel.BeamRelNode;
  import org.apache.beam.vendor.calcite.v1_40_0.com.google.common.collect.Table;
  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.metadata.MetadataDef;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.metadata.MetadataHandler;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.metadata.ReflectiveRelMetadataProvider;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.metadata.RelMetadataProvider;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.metadata.RelMetadataQuery;
  
  /**
   * This is the implementation of NodeStatsMetadata. Methods to estimate rate and row count for
   * Calcite's logical nodes be implemented here.
   */
  @SuppressWarnings({
    "rawtypes" // TODO(https://github.com/apache/beam/issues/20447)
  })
  public class RelMdNodeStats implements MetadataHandler<NodeStatsMetadata> {
  
    public static final RelMetadataProvider SOURCE =
        ReflectiveRelMetadataProvider.reflectiveSource(
            NodeStatsMetadata.METHOD, new RelMdNodeStats());
  
    @Override
    public MetadataDef<NodeStatsMetadata> getDef() {
      return NodeStatsMetadata.DEF;
    }
  
    @SuppressWarnings("UnusedDeclaration")
    public NodeStats getNodeStats(RelNode rel, RelMetadataQuery mq) {
      assert mq instanceof BeamRelMetadataQuery;
      BeamRelMetadataQuery bmq = (BeamRelMetadataQuery) mq;
  
      if (rel instanceof BeamRelNode) {
        return this.getBeamNodeStats((BeamRelNode) rel, bmq);
      }
  
      // We can later define custom methods for all different RelNodes to prevent hitting this point.
      // Similar to RelMdRowCount in calcite.
  
      return NodeStats.UNKNOWN;
    }
  
    private NodeStats getBeamNodeStats(BeamRelNode rel, BeamRelMetadataQuery mq) {
  
      // Removing the unknown results.
      // Calcite caches previous results in mq.map. This is done to prevent cyclic calls of this
      // method and also improving the performance. However, we might have returned an unknown result
      // because one of the inputs of the node was unknown (it is a logical node that we have not
      // implemented getNodeStats for it). Later we should not get the Unknown, therefore we need to
      // remove unknown results everyTime that this method is called.
      // Results are also cached in CachingRelMetadataProvider because calcite PlannerImpl#Transform
      // wraps the metadata provider with CachingRelMetadataProvider. However,
      // CachingRelMetadataProvider checks timestamp before returning previous results. Therefore,
      // there wouldn't be a problem in that case.
      List<Table.Cell<RelNode, ?, Object>> keys =
          mq.map.cellSet().stream()
              .filter(entry -> entry != null)
              .filter(entry -> entry.getValue() != null)
              .filter(entry -> entry.getValue() instanceof NodeStats)
              .filter(entry -> checkArgumentNotNull((NodeStats) entry.getValue()).isUnknown())
              .collect(Collectors.toList());
  
      keys.forEach(cell -> mq.map.remove(cell.getRowKey(), cell.getColumnKey()));
  
      return rel.estimateNodeStats(mq);
    }
  }
  