/*
* 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.List;
/**
* Named expression that accepts parameters and returns a result.
*
* <p>The application may occur at compile time (for a macro) or at run time
* (for a regular function). The result may be a relation, and so might any of
* the parameters.</p>
*
* <p>Functions are registered in a {@link Schema}, and may be queried by name
* ({@link Schema#getFunctions(String)}) then overloads resolved based on
* parameter types.</p>
*
* @see TableMacro
* @see ScalarFunction
*/
public interface Function {
/**
* Returns the parameters of this function.
*
* @return Parameters; never null
*/
List<FunctionParameter> getParameters();
}
// End Function.java