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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.linq4j.Ord;
import com.hazelcast.org.apache.calcite.linq4j.tree.BlockBuilder;
import com.hazelcast.org.apache.calcite.linq4j.tree.Expression;
import com.hazelcast.org.apache.calcite.linq4j.tree.Expressions;
import com.hazelcast.org.apache.calcite.plan.RelOptCluster;
import com.hazelcast.org.apache.calcite.plan.RelTraitSet;
import com.hazelcast.org.apache.calcite.rel.RelNode;
import com.hazelcast.org.apache.calcite.rel.core.Union;
import com.hazelcast.org.apache.calcite.util.BuiltInMethod;

import java.util.List;

/** Implementation of {@link com.hazelcast.org.apache.calcite.rel.core.Union} in
 * {@link com.hazelcast.org.apache.calcite.adapter.enumerable.EnumerableConvention enumerable calling convention}. */
public class EnumerableUnion extends Union implements EnumerableRel {
  public EnumerableUnion(RelOptCluster cluster, RelTraitSet traitSet,
      List inputs, boolean all) {
    super(cluster, traitSet, inputs, all);
  }

  public EnumerableUnion copy(RelTraitSet traitSet, List inputs,
      boolean all) {
    return new EnumerableUnion(getCluster(), traitSet, inputs, all);
  }

  public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
    final BlockBuilder builder = new BlockBuilder();
    Expression unionExp = null;
    for (Ord ord : Ord.zip(inputs)) {
      EnumerableRel input = (EnumerableRel) ord.e;
      final Result result = implementor.visitChild(this, ord.i, input, pref);
      Expression childExp =
          builder.append(
              "child" + ord.i,
              result.block);

      if (unionExp == null) {
        unionExp = childExp;
      } else {
        unionExp = all
            ? Expressions.call(unionExp, BuiltInMethod.CONCAT.method, childExp)
            : Expressions.call(unionExp,
                BuiltInMethod.UNION.method,
                Expressions.list(childExp)
                    .appendIfNotNull(result.physType.comparer()));
      }
    }

    builder.add(unionExp);
    final PhysType physType =
        PhysTypeImpl.of(
            implementor.getTypeFactory(),
            getRowType(),
            pref.prefer(JavaRowFormat.CUSTOM));
    return implementor.result(physType, builder.toBlock());
  }
}