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.interpreter;
  
  import org.apache.calcite.rel.core.SetOp;
  
  import com.google.common.collect.HashMultiset;
  
  import java.util.Collection;
  import java.util.HashSet;
  
  /**
   * Interpreter node that implements a
   * {@link org.apache.calcite.rel.core.SetOp},
   * including {@link org.apache.calcite.rel.core.Minus},
   * {@link org.apache.calcite.rel.core.Union} and
   * {@link org.apache.calcite.rel.core.Intersect}.
   */
  public class SetOpNode implements Node {
    private final Source leftSource;
    private final Source rightSource;
    private final Sink sink;
    private final SetOp setOp;
  
    public SetOpNode(Compiler compiler, SetOp setOp) {
      leftSource = compiler.source(setOp, 0);
      rightSource = compiler.source(setOp, 1);
      sink = compiler.sink(setOp);
      this.setOp = setOp;
    }
  
    @Override public void close() {
      leftSource.close();
      rightSource.close();
    }
  
    @Override public void run() throws InterruptedException {
      final Collection<Row> leftRows;
      final Collection<Row> rightRows;
      if (setOp.all) {
        leftRows = HashMultiset.create();
        rightRows = HashMultiset.create();
      } else {
        leftRows = new HashSet<>();
        rightRows = new HashSet<>();
      }
      Row row;
      while ((row = leftSource.receive()) != null) {
        leftRows.add(row);
      }
      while ((row = rightSource.receive()) != null) {
        rightRows.add(row);
      }
      switch (setOp.kind) {
      case INTERSECT:
        for (Row leftRow : leftRows) {
          if (rightRows.remove(leftRow)) {
            sink.send(leftRow);
          }
        }
        break;
      case EXCEPT:
        for (Row leftRow : leftRows) {
          if (!rightRows.remove(leftRow)) {
            sink.send(leftRow);
          }
        }
        break;
      case UNION:
        leftRows.addAll(rightRows);
        for (Row r : leftRows) {
          sink.send(r);
        }
        break;
      default:
        break;
      }
    }
  }
  