Re: Registering RawType with LegacyTypeInfo via Flink CREATE TABLE DDL

Posted by Yuval Itzchakov on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Registering-RawType-with-LegacyTypeInfo-via-Flink-CREATE-TABLE-DDL-tp40289p40327.html

Hi Timo,

Thanks for the explanation. Passing around a byte array is not possible since I need to know the concrete type later for serialization in my sink, so I need to keep the type.

What I'm trying to achieve is the following:

I have a scalar UDF function:

This function is later used in processing of a Flink table, by calling PARSE_JSON on the selected field.

Whoever uses these UDFs isn't aware of any Flink syntax for creating and registering tables, I generate the CREATE TABLE statement behind the scenes, dynamically.

for each table. In order for this to work, I need the UDF to output the correct type (in this example, io.circe.Json). Later, this JSON type (or any other type returned by the UDF for that matter) will get serialized in a custom sink and into a data warehouse (that's why I need to keep the concrete type, since serialization happens at the edges before writing it out).

The reason I'm converting between Table and DataStream is that this table will be further manipulated before being written to the custom DynamicTableSink by applying transformations on a DataStream[Row], and then converted back to a Table to be used in an additional CREATE TABLE and then INSERT INTO statement.

This is why I have these conversions back and forth, and why I somehow need a way to register the legacy types as a valid type of the table.

Hope that clarifies a bit, since the pipeline is rather complex I can't really share a MVCE of it.

On Mon, Dec 28, 2020 at 11:08 AM Timo Walther <[hidden email]> wrote:

Hi Yuval,

the legacy type has no string representation that can be used in a SQL
DDL statement. The current string representation LEGACY(...) is only a
temporary work around to persist the old types in catalogs.

Until FLIP-136 is fully implemented, toAppendStream/toRetractStream
support only legacy type info. So I would recommend to use the legacy
type in the UDF return type as well. Either you use the old
`getResultType` method or you override `getTypeInference` and call
`TypeConversions.fromLegacyInfoToDataType`.

Another work around could be that you simply use `BYTES` as the return
type and pass around a byte array instead.

Maybe you can show us a little end-to-end example, what you are trying
to achieve?

Regards,
Timo


On 28.12.20 07:47, Yuval Itzchakov wrote:
> Hi Danny,
>
> Yes, I tried implementing the DataTypeFactory for the UDF using
> TypeInformationRawType (which is deprecated BTW, and there's no support
> for RawType in the conversion), didn't help.
>
> I did manage to get the conversion working using
> TableEnvironment.toAppendStream (I was previously directly calling
> TypeConversions) but still remains the problem that Flink can't register
> LEGACY types via the CREATE TABLE DDL
>
> On Mon, Dec 28, 2020, 04:25 Danny Chan <[hidden email]
> <mailto:[hidden email]>> wrote:
>
>      > SQL parse failed. Encount
>     What syntax did you use ?
>
>      > TypeConversions.fromDataTypeToLegacyInfo cannot convert a plain
>     RAW type back to TypeInformation.
>
>     Did you try to construct type information by a new
>     fresh TypeInformationRawType ?
>
>     Yuval Itzchakov <[hidden email] <mailto:[hidden email]>> 于
>     2020年12月24日周四 下午7:24写道：
>
>         An expansion to my question:
>
>         What I really want is for the UDF to return `RAW(io.circe.Json,
>         ?)` type, but I have to do a conversion between Table and
>         DataStream, and TypeConversions.fromDataTypeToLegacyInfo cannot
>         convert a plain RAW type back to TypeInformation.
>
>         On Thu, Dec 24, 2020 at 12:59 PM Yuval Itzchakov
>         <[hidden email] <mailto:[hidden email]>> wrote:
>
>             Hi,
>
>             I have a UDF which returns a type of MAP<STRING,
>             LEGACY('RAW', 'ANY<io.circe.Json>')>. When I try to register
>             this type with Flink via the CREATE TABLE DDL, I encounter
>             an exception:
>
>             - SQL parse failed. Encountered "(" at line 2, column 256.
>             Was expecting one of:
>                  "NOT" ...
>                  "NULL" ...
>                  ">" ...
>                  "MULTISET" ...
>                  "ARRAY" ...
>                  "." ...
>
>             Which looks like the planner doesn't like the round brackets
>             on the LEGACY type. What is the correct way to register the
>             table with this type with Flink?
>             --
>             Best Regards,
>             Yuval Itzchakov.
>
>
>
>         --
>         Best Regards,
>         Yuval Itzchakov.
>

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