ScalarFunction.java

/**
 * 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.metamodel.query;

import org.apache.metamodel.data.Row;

/**
 * Interface that contains scalar specific methods.
 *
 * Scalar functions returns only a single value, based on the input value.
 *
 */
public interface ScalarFunction extends FunctionType {

    /**
     * Applies and evaluates the function on a particular row of data.
     * 
     * @param row
     *            the row containing data
     * @param parameters
     *            any parameters associated with the function call
     * @param operandItem
     *            the select item which is the argument to this function. If a
     *            function takes multiple select items, this will be the primary
     *            one.
     * @return
     */
    public Object evaluate(Row row, Object[] parameters, SelectItem operandItem);
}