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.enumerable;
  
  import org.apache.calcite.plan.Contexts;
  import org.apache.calcite.plan.Convention;
  import org.apache.calcite.plan.ConventionTraitDef;
  import org.apache.calcite.plan.RelOptPlanner;
  import org.apache.calcite.plan.RelTrait;
  import org.apache.calcite.plan.RelTraitDef;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelCollation;
  import org.apache.calcite.rel.RelCollations;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.RelFactories;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Family of calling conventions that return results as an
   * {@link org.apache.calcite.linq4j.Enumerable}.
   */
  public enum EnumerableConvention implements Convention {
    INSTANCE;
  
    /** Cost of an enumerable node versus implementing an equivalent node in a
     * "typical" calling convention. */
    public static final double COST_MULTIPLIER = 1.0d;
  
    @Override public String toString() {
      return getName();
    }
  
    @Override public Class getInterface() {
      return EnumerableRel.class;
    }
  
    @Override public String getName() {
      return "ENUMERABLE";
    }
  
    @Override public RelNode enforce(
        final RelNode input,
        final RelTraitSet required) {
      RelNode rel = input;
      if (input.getConvention() != INSTANCE) {
        rel =
            ConventionTraitDef.INSTANCE.convert(input.getCluster().getPlanner(),
                input, INSTANCE, true);
        requireNonNull(rel,
            () -> "Unable to convert input to " + INSTANCE + ", input = " + input);
      }
      RelCollation collation = required.getCollation();
      if (collation != null && collation != RelCollations.EMPTY) {
        rel = EnumerableSort.create(rel, collation, null, null);
      }
      return rel;
    }
  
    @Override public RelTraitDef getTraitDef() {
      return ConventionTraitDef.INSTANCE;
    }
  
    @Override public boolean satisfies(RelTrait trait) {
      return this == trait;
    }
  
    @Override public void register(RelOptPlanner planner) {}
  
    @Override public boolean canConvertConvention(Convention toConvention) {
      return false;
    }
  
    @Override public boolean useAbstractConvertersForConversion(RelTraitSet fromTraits,
        RelTraitSet toTraits) {
      return true;
    }
  
    @Override public RelFactories.Struct getRelFactories() {
      return RelFactories.Struct.fromContext(
              Contexts.of(
                  EnumerableRelFactories.ENUMERABLE_TABLE_SCAN_FACTORY,
                  EnumerableRelFactories.ENUMERABLE_PROJECT_FACTORY,
                  EnumerableRelFactories.ENUMERABLE_FILTER_FACTORY,
                  EnumerableRelFactories.ENUMERABLE_SORT_FACTORY));
    }
  }
  