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.adapter.cassandra;
  
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelOptCost;
  import org.apache.calcite.plan.RelOptPlanner;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelCollation;
  import org.apache.calcite.rel.RelFieldCollation;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Sort;
  import org.apache.calcite.rel.metadata.RelMetadataQuery;
  import org.apache.calcite.rel.type.RelDataTypeField;
  import org.apache.calcite.rex.RexNode;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Implementation of {@link org.apache.calcite.rel.core.Sort}
   * relational expression in Cassandra.
   */
  public class CassandraSort extends Sort implements CassandraRel {
    public CassandraSort(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode child, RelCollation collation) {
      super(cluster, traitSet, child, collation, null, null);
  
      assert getConvention() == CassandraRel.CONVENTION;
      assert getConvention() == child.getConvention();
    }
  
    @Override public @Nullable RelOptCost computeSelfCost(RelOptPlanner planner,
        RelMetadataQuery mq) {
      RelOptCost cost = requireNonNull(super.computeSelfCost(planner, mq));
      if (!collation.getFieldCollations().isEmpty()) {
        return cost.multiplyBy(0.05);
      } else {
        return cost;
      }
    }
  
    @Override public Sort copy(RelTraitSet traitSet, RelNode input,
        RelCollation newCollation, @Nullable RexNode offset, @Nullable RexNode fetch) {
      return new CassandraSort(getCluster(), traitSet, input, collation);
    }
  
    @Override public void implement(Implementor implementor) {
      implementor.visitChild(0, getInput());
  
      List<RelFieldCollation> sortCollations = collation.getFieldCollations();
      List<String> fieldOrder = new ArrayList<>();
      if (!sortCollations.isEmpty()) {
        // Construct a series of order clauses from the desired collation
        final List<RelDataTypeField> fields = getRowType().getFieldList();
        for (RelFieldCollation fieldCollation : sortCollations) {
          final String name =
              fields.get(fieldCollation.getFieldIndex()).getName();
          final String direction;
          switch (fieldCollation.getDirection()) {
          case DESCENDING:
            direction = "DESC";
            break;
          default:
            direction = "ASC";
          }
          fieldOrder.add(name + " " + direction);
        }
  
        implementor.addOrder(fieldOrder);
      }
    }
  }
  