org.apache.beam.sdk.extensions.sql.BeamSqlUdf Maven / Gradle / Ivy
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* 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,
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* 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;
import org.apache.beam.sdk.annotations.Experimental;
/**
* Interface to create a UDF in Beam SQL.
*
* A static method {@code eval} is required. Here is an example:
*
*
*
*
* 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);
* }
* }
*
*
*
* The first parameter is named "s" and is mandatory, and the second parameter is named "n" and
* is optional(always NULL if not specified).
*/
@Experimental
public interface BeamSqlUdf extends Serializable {
String UDF_METHOD = "eval";
}