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.RelOptRuleCall;
  import org.apache.calcite.plan.RelRule;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Sort;
  
  import org.immutables.value.Value;
  
  /**
   * Rule to convert an {@link org.apache.calcite.rel.core.Sort} that has
   * {@code offset} or {@code fetch} set to an
   * {@link EnumerableLimit}
   * on top of a "pure" {@code Sort} that has no offset or fetch.
   *
   * @see EnumerableRules#ENUMERABLE_LIMIT_RULE
   */
  @Value.Enclosing
  public class EnumerableLimitRule
      extends RelRule<EnumerableLimitRule.Config> {
    /** Creates an EnumerableLimitRule. */
    protected EnumerableLimitRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    EnumerableLimitRule() {
      this(Config.DEFAULT);
    }
  
    @Override public void onMatch(RelOptRuleCall call) {
      final Sort sort = call.rel(0);
      if (sort.offset == null && sort.fetch == null) {
        return;
      }
      RelNode input = sort.getInput();
      if (!sort.getCollation().getFieldCollations().isEmpty()) {
        // Create a sort with the same sort key, but no offset or fetch.
        input =
            sort.copy(sort.getTraitSet(), input, sort.getCollation(), null, null);
      }
      call.transformTo(
          EnumerableLimit.create(
              convert(call.getPlanner(), input,
                  input.getTraitSet().replace(EnumerableConvention.INSTANCE)),
              sort.offset,
              sort.fetch));
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableEnumerableLimitRule.Config.of()
          .withOperandSupplier(b -> b.operand(Sort.class).anyInputs());
  
      @Override default EnumerableLimitRule toRule() {
        return new EnumerableLimitRule(this);
      }
    }
  }
  