i was trying to query a postgresql table, and convert it to dataStream:

StreamExecutionEnvironment bsEnv = StreamExecutionEnvironment.getExecutionEnvironment();
StreamTableEnvironment tEnv = StreamTableEnvironment.create(bsEnv);
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            catalog config and register
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Table tb = tEnv.sqlQuery("SELECT * FROM mytable);
DataStream<Row> dataStream = tEnv.toDataStream(tb)  
dataStream.print();

But it seems that the datastream is empty..
the query is fine , when i print the TableResult i can see my table.

TableResult tb1 = tEnv.sqlQuery("SELECT * FROM mytable).execute();
tb1.print();

                     

is this the right way to do it?
i wondered because according to Table doc:
“A Table object describes a pipeline of data transformations. **It does not contain the data **itself in any way.”
so if its not containing the data, what the point by convert it to datastream?
or maybe the datastream supposed to hold the data?
thank you!