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.core;
  
  import org.apache.calcite.linq4j.Ord;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelOptUtil;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.AbstractRelNode;
  import org.apache.calcite.rel.RelInput;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.RelWriter;
  import org.apache.calcite.rel.hint.Hintable;
  import org.apache.calcite.rel.hint.RelHint;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.util.Util;
  
  import com.google.common.collect.ImmutableList;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  import static org.apache.calcite.sql.SqlKind.SET_QUERY;
  
  /**
   * <code>SetOp</code> is an abstract base for relational set operators such
   * as UNION, MINUS (aka EXCEPT), and INTERSECT.
   */
  public abstract class SetOp extends AbstractRelNode implements Hintable {
    //~ Instance fields --------------------------------------------------------
  
    protected ImmutableList<RelNode> inputs;
    public final SqlKind kind;
    public final boolean all;
    protected final ImmutableList<RelHint> hints;
  
    //~ Constructors -----------------------------------------------------------
  
    /**
     * Creates a SetOp.
     */
    protected SetOp(RelOptCluster cluster, RelTraitSet traits, List<RelHint> hints,
        List<RelNode> inputs, SqlKind kind, boolean all) {
      super(cluster, traits);
      checkArgument(SET_QUERY.contains(kind));
      this.kind = kind;
      this.inputs = ImmutableList.copyOf(inputs);
      this.all = all;
      this.hints = ImmutableList.copyOf(hints);
    }
  
    /**
     * Creates a SetOp.
     */
    protected SetOp(RelOptCluster cluster, RelTraitSet traits,
        List<RelNode> inputs, SqlKind kind, boolean all) {
      this(cluster, traits, Collections.emptyList(), inputs, kind, all);
    }
  
    /**
     * Creates a SetOp by parsing serialized output.
     */
    protected SetOp(RelInput input) {
      this(input.getCluster(), input.getTraitSet(), Collections.emptyList(),
          input.getInputs(), SqlKind.UNION, input.getBoolean("all", false));
    }
  
    //~ Methods ----------------------------------------------------------------
  
    public abstract SetOp copy(
        RelTraitSet traitSet,
        List<RelNode> inputs,
        boolean all);
  
    @Override public SetOp copy(RelTraitSet traitSet, List<RelNode> inputs) {
      return copy(traitSet, inputs, all);
    }
  
    @Override public void replaceInput(int ordinalInParent, RelNode p) {
      final List<RelNode> newInputs = new ArrayList<>(inputs);
      newInputs.set(ordinalInParent, p);
      inputs = ImmutableList.copyOf(newInputs);
      recomputeDigest();
    }
  
    @Override public List<RelNode> getInputs() {
      return inputs;
    }
  
    @Override public RelWriter explainTerms(RelWriter pw) {
      super.explainTerms(pw);
      for (Ord<RelNode> ord : Ord.zip(inputs)) {
        pw.input("input#" + ord.i, ord.e);
      }
      return pw.item("all", all);
    }
  
    @Override protected RelDataType deriveRowType() {
      final List<RelDataType> inputRowTypes =
          Util.transform(inputs, RelNode::getRowType);
      final RelDataType rowType =
          getCluster().getTypeFactory().leastRestrictive(inputRowTypes);
      if (rowType == null) {
        throw new IllegalArgumentException("Cannot compute compatible row type "
            + "for arguments to set op: "
            + Util.sepList(inputRowTypes, ", "));
      }
      return rowType;
    }
  
    @Override public ImmutableList<RelHint> getHints() {
      return hints;
    }
  
    /**
     * Returns whether all the inputs of this set operator have the same row
     * type as its output row.
     *
     * @param compareNames Whether column names are important in the
     *                     homogeneity comparison
     * @return Whether all the inputs of this set operator have the same row
     *   type as its output row
     */
    public boolean isHomogeneous(boolean compareNames) {
      RelDataType unionType = getRowType();
      for (RelNode input : getInputs()) {
        if (!RelOptUtil.areRowTypesEqual(
            input.getRowType(), unionType, compareNames)) {
          return false;
        }
      }
      return true;
    }
  }
  