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.rel.rules;
  
  import org.apache.calcite.plan.ConventionTraitDef;
  import org.apache.calcite.plan.RelOptRuleCall;
  import org.apache.calcite.plan.RelRule;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelCollation;
  import org.apache.calcite.rel.RelCollationTraitDef;
  import org.apache.calcite.rel.core.Sort;
  import org.apache.calcite.tools.RelBuilderFactory;
  
  import org.immutables.value.Value;
  
  /**
   * Planner rule that removes
   * a {@link org.apache.calcite.rel.core.Sort} if its input is already sorted.
   *
   * <p>Requires {@link RelCollationTraitDef}.
   *
   * @see CoreRules#SORT_REMOVE
   */
  @Value.Enclosing
  public class SortRemoveRule
      extends RelRule<SortRemoveRule.Config>
      implements TransformationRule {
  
    /** Creates a SortRemoveRule. */
    protected SortRemoveRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public SortRemoveRule(RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
          .as(Config.class));
    }
  
    @Override public void onMatch(RelOptRuleCall call) {
      if (!call.getPlanner().getRelTraitDefs()
          .contains(RelCollationTraitDef.INSTANCE)) {
        // Collation is not an active trait.
        return;
      }
      final Sort sort = call.rel(0);
      if (sort.offset != null || sort.fetch != null) {
        // Don't remove sort if would also remove OFFSET or LIMIT.
        return;
      }
      // Express the "sortedness" requirement in terms of a collation trait and
      // we can get rid of the sort. This allows us to use rels that just happen
      // to be sorted but get the same effect.
      final RelCollation collation = sort.getCollation();
      assert collation == sort.getTraitSet()
          .getTrait(RelCollationTraitDef.INSTANCE);
      final RelTraitSet traits = sort.getInput().getTraitSet()
          .replace(collation).replaceIf(ConventionTraitDef.INSTANCE, sort::getConvention);
      call.transformTo(convert(call.getPlanner(), sort.getInput(), traits));
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableSortRemoveRule.Config.of()
          .withOperandSupplier(b ->
              b.operand(Sort.class).anyInputs());
  
      @Override default SortRemoveRule toRule() {
        return new SortRemoveRule(this);
      }
    }
  }
  