我正在尝试使用表api中的unnest函数展平数组。
我是做错了什么还是它不是一个受支持的函数？但本页建议：https://ci.apache.org/projects/flink/flink-docs-master/dev/table/sql/queries.html
谢谢！
代码
python自定义项

@udf(input_types=DataTypes.STRING(), result_type=DataTypes.ARRAY(DataTypes.STRING()))
def explode(s):
    return 3*[s]

t_env.register_function("explode", explode)

处理

tab = t_env.from_path('mySource').select("id, explode(dummy) as dummy_list")
t_env.register_table("temp_table", tab)
t_env.sql_query("SELECT t.item as dummy_item FROM UNNEST(select dummy_list from temp_table) AS t(item)").insert_into("mySink")

执行

t_env.execute("dummy_unnest")

错误

TableException: Cannot generate a valid execution plan for the given query: 

LogicalProject(dummy_item=[$0])
  Uncollect
    LogicalProject(EXPR$0=[org$apache$flink$table$functions$python$PythonScalarFunction$908596b4671476ee325743dba92ed6c7($1)])
      LogicalTableScan(table=[[default_catalog, default_database, mySource]])

This exception indicates that the query uses an unsupported SQL feature.
Please check the documentation for the set of currently supported SQL features.