Computed Columns In Stream to Table Conversion

[Aeden Jameson]

Hi

   How does one specify computed columns when converting a DataStream
to a temporary view? For example

        final DataStream<Message> stream = env.addSource(..);

        tEnv.createTemporaryView(
                "myTable"
                stream
                ,$("col1")
                ,$("col2")
                ....
                ,$("Do computed columns work here?")
        );

More specifically the compute expression i'd like to use involves
'case when.... then 1 else 0 end'
--
Thank you,
Aeden

[Timo Walther]

Hi Aeden,

computed columns on a DataStrem input are currently not supported. I am
currently working on making this possible. Have a look at FLIP-136 for
more information [1].

However, you can simply add a projection before you register a view:

tEnv.createTemporaryView("myTable", dataStream);

tEnv.createTemporaryView(
     "myTableWithComputation",
     tEnv.sqlQuery("SELECT your_projection FROM myTable"))

I hope this helps.

Regards,
Timo


[1]
https://cwiki.apache.org/confluence/display/FLINK/FLIP-136%3A++Improve+interoperability+between+DataStream+and+Table+API


On 18.01.21 09:09, Aeden Jameson wrote:

> Hi
>
>     How does one specify computed columns when converting a DataStream
> to a temporary view? For example
>
>          final DataStream<Message> stream = env.addSource(..);
>
>          tEnv.createTemporaryView(
>                  "myTable"
>                  stream
>                  ,$("col1")
>                  ,$("col2")
>                  ....
>                  ,$("Do computed columns work here?")
>          );
>
> More specifically the compute expression i'd like to use involves
> 'case when.... then 1 else 0 end'
>