/*
* 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 net.hydromatic.optiq;
import java.util.BitSet;
/**
* Statistics about a {@link Table}.
*
* <p>Each of the methods may return {@code null} meaning "not known".</p>
*
* @see Statistics
*/
public interface Statistic {
/** Returns the approximate number of rows in the table. */
Double getRowCount();
/** Returns whether the given set of columns is a unique key, or a superset
* of a unique key, of the table.
*/
boolean isKey(BitSet columns);
}
// End Statistic.java