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.spark;
  
  import org.apache.calcite.adapter.enumerable.EnumerableConvention;
  import org.apache.calcite.adapter.enumerable.JavaRowFormat;
  import org.apache.calcite.adapter.enumerable.PhysType;
  import org.apache.calcite.adapter.enumerable.PhysTypeImpl;
  import org.apache.calcite.linq4j.tree.BlockBuilder;
  import org.apache.calcite.linq4j.tree.Expression;
  import org.apache.calcite.linq4j.tree.Expressions;
  import org.apache.calcite.plan.ConventionTraitDef;
  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.convert.ConverterImpl;
  import org.apache.calcite.rel.metadata.RelMetadataQuery;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Relational expression that converts input of {@link EnumerableConvention}
   * into {@link SparkRel#CONVENTION Spark convention}.
   *
   * <p>Concretely, this means iterating over the contents of an
   * {@link org.apache.calcite.linq4j.Enumerable}, storing them in a list, and
   * building an {@link org.apache.spark.rdd.RDD} on top of it.
   */
  public class EnumerableToSparkConverter
      extends ConverterImpl
      implements SparkRel {
    protected EnumerableToSparkConverter(RelOptCluster cluster,
        RelTraitSet traits, RelNode input) {
      super(cluster, ConventionTraitDef.INSTANCE, traits, input);
    }
  
    @Override public RelNode copy(RelTraitSet traitSet, List<RelNode> inputs) {
      return new EnumerableToSparkConverter(
          getCluster(), traitSet, sole(inputs));
    }
  
    @Override public @Nullable RelOptCost computeSelfCost(RelOptPlanner planner,
        RelMetadataQuery mq) {
      final RelOptCost cost = requireNonNull(super.computeSelfCost(planner, mq));
      return cost.multiplyBy(.01);
    }
  
    @Override public Result implementSpark(Implementor implementor) {
      // Generate:
      //   Enumerable source = ...;
      //   return SparkRuntime.createRdd(sparkContext, source);
      if (true) {
        throw new RuntimeException("EnumerableToSparkConverter is not implemented");
      }
      final BlockBuilder list = new BlockBuilder();
      final PhysType physType =
          PhysTypeImpl.of(
              implementor.getTypeFactory(), getRowType(),
              JavaRowFormat.CUSTOM);
      final Expression source = null; // TODO:
      final Expression sparkContext =
          Expressions.call(
              SparkMethod.GET_SPARK_CONTEXT.method,
              implementor.getRootExpression());
      final Expression rdd =
          list.append(
              "rdd",
              Expressions.call(
                  SparkMethod.CREATE_RDD.method,
                  sparkContext,
                  source));
      list.add(
          Expressions.return_(null, rdd));
      return implementor.result(physType, list.toBlock());
    }
  }
  