exec/java-exec/src/main/java/org/apache/drill/exec/planner/physical/SortConvertPrule.java

/*
 * 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.drill.exec.planner.physical;

import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.Sort;
import org.apache.calcite.rel.convert.ConverterRule;
import org.apache.calcite.plan.Convention;
import org.apache.calcite.plan.RelOptRule;
import org.apache.calcite.plan.RelOptRuleCall;

/**
 * Rule that converts an {@link Sort} to a physical {@link SortPrel}, implemented by a Drill "order" operation.
 *
 * The {@link Sort} is added in optiq's AbstractConvert call, when it enforces certain "order" to the input stream.
 * Drill uses this rule to convert such sort enforcer into physical {@link SortPrel}.
 */
public class SortConvertPrule extends ConverterRule {
  public static final RelOptRule INSTANCE = new SortConvertPrule("SortConvertPrule", Convention.NONE);
  //public static final RelOptRule INSTANCE_SRC_LOGICAL = new SortPrule("SortPrule:Src_Logical", DrillRel.DRILL_LOGICAL);

  private SortConvertPrule(String description, Convention srcConvention) {
    super(Config.INSTANCE
      .withConversion(Sort.class, srcConvention, Prel.DRILL_PHYSICAL, description));
  }

  @Override
  public boolean matches(RelOptRuleCall call) {
    final Sort sort = call.rel(0);
    return sort.offset == null && sort.fetch == null;
  }

  @Override
  public RelNode convert(RelNode r) {
    Sort rel = (Sort) r;
    RelTraitSet traits = rel.getInput().getTraitSet().replace(Prel.DRILL_PHYSICAL);
    return new SortPrel(rel.getCluster(),
                        traits.plus(rel.getCollation()),
                        convert(rel.getInput(), traits.simplify()),
                        rel.getCollation());
  }
}