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.RelNode;
  import org.apache.calcite.rel.core.Project;
  import org.apache.calcite.rel.metadata.RelMetadataQuery;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.util.Pair;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.ImmutableSet;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Implementation of {@link org.apache.calcite.rel.core.Project}
   * relational expression in Cassandra.
   */
  public class CassandraProject extends Project implements CassandraRel {
    public CassandraProject(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode input, List<? extends RexNode> projects, RelDataType rowType) {
      super(cluster, traitSet, ImmutableList.of(), input, projects, rowType, ImmutableSet.of());
      assert getConvention() == CassandraRel.CONVENTION;
      assert getConvention() == input.getConvention();
    }
  
    @Override public Project copy(RelTraitSet traitSet, RelNode input,
        List<RexNode> projects, RelDataType rowType) {
      return new CassandraProject(getCluster(), traitSet, input, projects,
          rowType);
    }
  
    @Override public @Nullable RelOptCost computeSelfCost(RelOptPlanner planner,
        RelMetadataQuery mq) {
      final RelOptCost cost = super.computeSelfCost(planner, mq);
      return requireNonNull(cost, "cost").multiplyBy(0.1);
    }
  
    @Override public void implement(Implementor implementor) {
      implementor.visitChild(0, getInput());
      final CassandraRules.RexToCassandraTranslator translator =
          new CassandraRules.RexToCassandraTranslator(
              CassandraRules.cassandraFieldNames(getInput().getRowType()));
      final Map<String, String> fields = new LinkedHashMap<>();
      for (Pair<RexNode, String> pair : getNamedProjects()) {
        final RexNode node = pair.left;
        final String name = pair.right;
        final String originalName = node.accept(translator);
        fields.put(originalName, name);
      }
      implementor.add(fields, null);
    }
  }
  