You are viewing an old version of this page. View the current version.

Compare with Current View Page History

Version 1 Next »


Status

Current state: "Under Discussion"

Discussion thread: http://apache-flink-mailing-list-archive.1008284.n3.nabble.com/DISCUSS-Flink-Python-UDF-Environment-and-Dependency-Management-td33514.html

JIRA: FLINK-14019

Released: 

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

This proposal aims to support function DDL with the consideration of SQL syntax, language compliance, and advanced external UDF lib registration. The Flink DDL is initialized and discussed in the design [1] by Shuyi Chen and Timo. As the initial discussion mainly focused on the table, type and view. FLIP-69 [2] extend it with a more detailed discussion of DDL for catalog, database, and function. Original the function DDL was under the scope of FLIP-69. After some discussion with the community, we found that there are several ongoing efforts, such as FLIP-64 [3], FLIP-65 [4], and FLIP-78 [5]. As they will directly impact the SQL syntax of function DDL, the proposal wants to describe the problem clearly with the consideration of existing works and make sure the design aligns with efforts of API change of temporary objects and type inference for UDF defined by different languages.

Proposed Changes

Requirements

Before deep into the DDL SQL, we want to discuss the major requirements for defining a function within Flink runtime by related FLIPs:

  • External lib registration. The requirements come from the hive integration that enhances the adoption of Flink batch. HQL supports syntax like:

    CREATE FUNCTION addfunc AS 'com.example.hiveserver2.udf.add' USING JAR 'hdfs:///path/to/jar'

  • Language distinguish. Due to bytecode language specifics in Scala, there are some limitations to extract type information from scala function. At the same time, support python UDF in table runtime is another ongoing effort. Thus, the SQL syntax consider support multiple languages. Mysql create function syntax support language in this way:

    CREATE FUNCTION hello (s CHAR(20))RETURNS CHAR(50)DETERMINISTIC RETURN CONCAT('Hello, ',s,'!') LANGUAGE SQL 
  • No labels