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.JavaRelImplementor;
  import org.apache.calcite.adapter.enumerable.PhysType;
  import org.apache.calcite.linq4j.tree.BlockStatement;
  import org.apache.calcite.plan.Convention;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rex.RexBuilder;
  
  /**
   * Relational expression that uses Spark calling convention.
   */
  public interface SparkRel extends RelNode {
    Result implementSpark(Implementor implementor);
  
    /** Calling convention for relational operations that occur in Spark. */
    Convention CONVENTION = new Convention.Impl("SPARK", SparkRel.class);
  
    /** Extension to {@link JavaRelImplementor} that can handle Spark relational
     * expressions. */
    abstract class Implementor extends JavaRelImplementor {
      protected Implementor(RexBuilder rexBuilder) {
        super(rexBuilder);
      }
  
      abstract Result result(PhysType physType, BlockStatement blockStatement);
  
      abstract Result visitInput(SparkRel parent, int ordinal, SparkRel input);
    }
  
    /** Result of generating Java code to implement a Spark relational
     * expression. */
    class Result {
      public final BlockStatement block;
      public final PhysType physType;
  
      public Result(PhysType physType, BlockStatement block) {
        this.physType = physType;
        this.block = block;
      }
    }
  }
  