Получил pyflink.util.exceptions.TableException: findAndCreateTableSource не удалось. при запуске примера PyFlink

Я использую программу PyFlink (скопировано из https://ci.apache.org/projects/flink/flink-docs-release-1.12/dev/python/table_api_tutorial.html)

from pyflink.dataset import ExecutionEnvironment
from pyflink.table import TableConfig, DataTypes, BatchTableEnvironment
from pyflink.table.descriptors import Schema, OldCsv, FileSystem
from pyflink.table.expressions import lit

exec_env = ExecutionEnvironment.get_execution_environment()
exec_env.set_parallelism(1)
t_config = TableConfig()
t_env = BatchTableEnvironment.create(exec_env, t_config)

t_env.connect(FileSystem().path('/tmp/input')) \
    .with_format(OldCsv()
                 .field('word', DataTypes.STRING())) \
    .with_schema(Schema()
                 .field('word', DataTypes.STRING())) \
    .create_temporary_table('mySource')

t_env.connect(FileSystem().path('/tmp/output')) \
    .with_format(OldCsv()
                 .field_delimiter('\t')
                 .field('word', DataTypes.STRING())
                 .field('count', DataTypes.BIGINT())) \
    .with_schema(Schema()
                 .field('word', DataTypes.STRING())
                 .field('count', DataTypes.BIGINT())) \
    .create_temporary_table('mySink')

tab = t_env.from_path('mySource')
tab.group_by(tab.word) \
   .select(tab.word, lit(1).count) \
   .execute_insert('mySink').wait()

Чтобы убедиться, что он работает, я сделал следующее по порядку:

1. Запустите echo -e "flink\npyflink\nflink" > /tmp/input
2. Запустите python WordCount.py
3. Запустите cat /tmp/out и найдите ожидаемый результат

Затем я немного изменил свою программу PyFlink, чтобы предпочесть SQL API таблицам, но я обнаружил, что это не работает.

from pyflink.dataset import ExecutionEnvironment
from pyflink.table import TableConfig, DataTypes, BatchTableEnvironment
from pyflink.table.descriptors import Schema, OldCsv, FileSystem
from pyflink.table.expressions import lit

exec_env = ExecutionEnvironment.get_execution_environment()
exec_env.set_parallelism(1)
t_config = TableConfig()
t_env = BatchTableEnvironment.create(exec_env, t_config)

my_source_ddl = """
    create table mySource (
        word VARCHAR
    ) with (
        'connector' = 'filesystem',
        'format' = 'csv',
        'path' = '/tmp/input'
    )
"""

my_sink_ddl = """
    create table mySink (
        word VARCHAR,
        `count` BIGINT
    ) with (
        'connector' = 'filesystem',
        'format' = 'csv',
        'path' = '/tmp/output'
    )
"""

t_env.sql_update(my_source_ddl)
t_env.sql_update(my_sink_ddl)

tab = t_env.from_path('mySource')
tab.group_by(tab.word) \
   .select(tab.word, lit(1).count) \
   .execute_insert('mySink').wait()

Вот ошибка:

Traceback (most recent call last):
  File "WordCount.py", line 38, in <module>
    .execute_insert('mySink').wait()
  File "/usr/local/anaconda3/envs/pyflink-quickstart/lib/python3.7/site-packages/pyflink/table/table.py", line 864, in execute_insert
    return TableResult(self._j_table.executeInsert(table_path, overwrite))
  File "/usr/local/anaconda3/envs/pyflink-quickstart/lib/python3.7/site-packages/py4j/java_gateway.py", line 1286, in __call__
    answer, self.gateway_client, self.target_id, self.name)
  File "/usr/local/anaconda3/envs/pyflink-quickstart/lib/python3.7/site-packages/pyflink/util/exceptions.py", line 162, in deco
    raise java_exception
pyflink.util.exceptions.TableException: findAndCreateTableSink failed.
     at org.apache.flink.table.factories.TableFactoryUtil.findAndCreateTableSink(TableFactoryUtil.java:87)
     at org.apache.flink.table.api.internal.TableEnvImpl.getTableSink(TableEnvImpl.scala:1097)
     at org.apache.flink.table.api.internal.TableEnvImpl.org$apache$flink$table$api$internal$TableEnvImpl$$writeToSinkAndTranslate(TableEnvImpl.scala:929)
     at org.apache.flink.table.api.internal.TableEnvImpl$$anonfun$1.apply(TableEnvImpl.scala:556)
     at org.apache.flink.table.api.internal.TableEnvImpl$$anonfun$1.apply(TableEnvImpl.scala:554)
     at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
     at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
     at scala.collection.Iterator$class.foreach(Iterator.scala:891)
     at scala.collection.AbstractIterator.foreach(Iterator.scala:1334)
     at scala.collection.IterableLike$class.foreach(IterableLike.scala:72)
     at scala.collection.AbstractIterable.foreach(Iterable.scala:54)
     at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
     at scala.collection.AbstractTraversable.map(Traversable.scala:104)
     at org.apache.flink.table.api.internal.TableEnvImpl.executeInternal(TableEnvImpl.scala:554)
     at org.apache.flink.table.api.internal.TableImpl.executeInsert(TableImpl.java:572)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
     at java.lang.reflect.Method.invoke(Method.java:498)
     at org.apache.flink.api.python.shaded.py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:244)
     at org.apache.flink.api.python.shaded.py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)
     at org.apache.flink.api.python.shaded.py4j.Gateway.invoke(Gateway.java:282)
     at org.apache.flink.api.python.shaded.py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132)
     at org.apache.flink.api.python.shaded.py4j.commands.CallCommand.execute(CallCommand.java:79)
     at org.apache.flink.api.python.shaded.py4j.GatewayConnection.run(GatewayConnection.java:238)
     at java.lang.Thread.run(Thread.java:748)

Интересно, что не так с моей новой программой?