[FLINK-28528] Table.getSchema fails on table with watermark

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.15.1
• Component/s: API / Python
• Assignee: Xingbo Huang
• Reporter: Xuannan Su
• Created: 13/Jul/22 02:19
• Updated: 07/Apr/23 05:23

Description

The bug can be reproduced with the following test. The test can pass if we use the commented way to define the watermark.

    def test_flink_2(self):
        env = StreamExecutionEnvironment.get_execution_environment()
        t_env = StreamTableEnvironment.create(env)
        table = t_env.from_descriptor(
            TableDescriptor.for_connector("filesystem")
            .schema(
                Schema.new_builder()
                .column("name", DataTypes.STRING())
                .column("cost", DataTypes.INT())
                .column("distance", DataTypes.INT())
                .column("time", DataTypes.TIMESTAMP(3))
                .watermark("time", expr.col("time") - expr.lit(60).seconds)
                # .watermark("time", "`time` - INTERVAL '60' SECOND")
                .build()
            )
            .format("csv")
            .option("path", "./input.csv")
            .build()
        )

        print(table.get_schema())

It causes the following exception

E       pyflink.util.exceptions.TableException: org.apache.flink.table.api.TableException: Expression 'minus(time, 60000)' is not string serializable. Currently, only expressions that originated from a SQL expression have a well-defined string representation.
E       	at org.apache.flink.table.expressions.ResolvedExpression.asSerializableString(ResolvedExpression.java:51)
E       	at org.apache.flink.table.api.TableSchema.lambda$fromResolvedSchema$13(TableSchema.java:455)
E       	at java.util.Collections$SingletonList.forEach(Collections.java:4824)
E       	at org.apache.flink.table.api.TableSchema.fromResolvedSchema(TableSchema.java:451)
E       	at org.apache.flink.table.api.Table.getSchema(Table.java:101)
E       	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
E       	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
E       	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
E       	at java.lang.reflect.Method.invoke(Method.java:498)
E       	at org.apache.flink.api.python.shaded.py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:244)
E       	at org.apache.flink.api.python.shaded.py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)
E       	at org.apache.flink.api.python.shaded.py4j.Gateway.invoke(Gateway.java:282)
E       	at org.apache.flink.api.python.shaded.py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132)
E       	at org.apache.flink.api.python.shaded.py4j.commands.CallCommand.execute(CallCommand.java:79)
E       	at org.apache.flink.api.python.shaded.py4j.GatewayConnection.run(GatewayConnection.java:238)
E       	at java.lang.Thread.run(Thread.java:748)