/*
 * 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.eigenbase.rel;

import java.util.BitSet;
import java.util.List;

import org.eigenbase.rel.metadata.RelMetadataQuery;
import org.eigenbase.relopt.RelOptCluster;
import org.eigenbase.relopt.RelTraitSet;
import org.eigenbase.sql.SqlKind;

/**
 * Abstract base class for implementations of
 * {@link MinusRel}.
 */
public abstract class MinusRelBase extends SetOpRel {
  public MinusRelBase(
      RelOptCluster cluster,
      RelTraitSet traits,
      List<RelNode> inputs,
      boolean all) {
    super(cluster, traits, inputs, SqlKind.EXCEPT, all);
  }

  /**
   * Creates a MinusRelBase by parsing serialized output.
   */
  protected MinusRelBase(RelInput input) {
    super(input);
  }

  @Override
  public double getRows() {
    // REVIEW jvs 30-May-2005:  I just pulled this out of a hat.
    double dRows = RelMetadataQuery.getRowCount(inputs.get(0));
    for (int i = 1; i < inputs.size(); i++) {
      dRows -= 0.5 * RelMetadataQuery.getRowCount(inputs.get(i));
    }
    if (dRows < 0) {
      dRows = 0;
    }
    return dRows;
  }

  @Override
  public boolean isKey(BitSet columns) {
    return inputs.get(0).isKey(columns)
        || super.isKey(columns);
  }
}

// End MinusRelBase.java