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/*
 * 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 com.hazelcast.org.apache.calcite.adapter.enumerable;

import com.hazelcast.org.apache.calcite.plan.RelOptRule;
import com.hazelcast.org.apache.calcite.plan.RelOptRuleCall;
import com.hazelcast.org.apache.calcite.rel.RelNode;
import com.hazelcast.org.apache.calcite.rel.core.Sort;

/**
 * Rule to convert an {@link com.hazelcast.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.
 */
class EnumerableLimitRule extends RelOptRule {
  EnumerableLimitRule() {
    super(
        operand(Sort.class, any()),
        "EnumerableLimitRule");
  }

  @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(input, input.getTraitSet().replace(EnumerableConvention.INSTANCE)),
            sort.offset,
            sort.fetch));
  }
}