| /* |
| * 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.beam.sdk.extensions.sql; |
| |
| import java.io.Serializable; |
| |
| /** |
| * Interface to create a UDF in Beam SQL. |
| * |
| * <p>A static method {@code eval} is required. Here is an example: |
| * |
| * <blockquote> |
| * |
| * <pre> |
| * public static class MyLeftFunction { |
| * public String eval( |
| * @Parameter(name = "s") String s, |
| * @Parameter(name = "n", optional = true) Integer n) { |
| * return s.substring(0, n == null ? 1 : n); |
| * } |
| * }</pre> |
| * |
| * </blockquote> |
| * |
| * <p>The first parameter is named "s" and is mandatory, and the second parameter is named "n" and |
| * is optional(always NULL if not specified). |
| */ |
| public interface BeamSqlUdf extends Serializable { |
| String UDF_METHOD = "eval"; |
| } |