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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.Convention;
import com.hazelcast.org.apache.calcite.plan.RelTraitSet;
import com.hazelcast.org.apache.calcite.rel.RelNode;
import com.hazelcast.org.apache.calcite.rel.convert.ConverterRule;
import com.hazelcast.org.apache.calcite.rel.core.Union;
import com.hazelcast.org.apache.calcite.rel.logical.LogicalUnion;
import com.hazelcast.org.apache.calcite.util.Util;

import java.util.List;

/**
 * Rule to convert an {@link LogicalUnion} to an {@link EnumerableUnion}.
 * You may provide a custom config to convert other nodes that extend {@link Union}.
 *
 * @see EnumerableRules#ENUMERABLE_UNION_RULE
 */
class EnumerableUnionRule extends ConverterRule {
  /** Default configuration. */
  static final Config DEFAULT_CONFIG = Config.INSTANCE
      .withConversion(LogicalUnion.class, Convention.NONE,
          EnumerableConvention.INSTANCE, "EnumerableUnionRule")
      .withRuleFactory(EnumerableUnionRule::new);

  /** Called from the Config. */
  protected EnumerableUnionRule(Config config) {
    super(config);
  }

  @Override public RelNode convert(RelNode rel) {
    final Union union = (Union) rel;
    final EnumerableConvention out = EnumerableConvention.INSTANCE;
    final RelTraitSet traitSet = rel.getCluster().traitSet().replace(out);
    final List newInputs = Util.transform(
        union.getInputs(), n -> convert(n, traitSet));
    return new EnumerableUnion(rel.getCluster(), traitSet,
        newInputs, union.all);
  }
}