[FLINK-21856] Fix the bug of using Python UDF from sub-query as input param of Python UDTF

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.11.3, 1.12.2, 1.13.0
• Component/s: API / Python
• Labels: auto-deprioritized-major
• Assignee: Unassigned
• Reporter: Huang Xingbo
• Created: 18/Mar/21 08:18
• Updated: 18/Aug/21 08:02
• Resolved: 18/Aug/21 08:02

Description

This example comes from the user. splitStr is a Python UDTF. train_and_predict is a Python UDF.

t_env.sql_query("""
 select A.hotime ,
         A.before_ta ,
         A.before_rssi ,
         A.after_ta ,
         A.after_rssil ,
         A.nb_tath ,
         A.nb_rssith ,
         nbr_rssi ,
         nbr_ta
 from (SELECT
     hotime ,
     before_ta ,
     before_rssi ,
     after_ta ,
     after_rssil ,
     nb_tath ,
     nb_rssith ,
     train_and_predict(nb_tath, nb_rssith) predict
 FROM
     source) as  A,LATERAL TABLE(splitStr(predict)) as T(nbr_rssi, nbr_ta)
 """)

The root cause is that `train_and_predict` is a RexCorrelVariable which we don't have relevant logic to deal with.

A workaround is to use the Table API.