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https://issues.apache.org/jira/browse/FLINK-18782?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17168704#comment-17168704
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Jark Wu commented on FLINK-18782:
---------------------------------
Hi, currenlty, Flink Table/SQL API does't provide the guarantee to keep retain
the field names for the TypeInformation of {{toAppendStream}}. But I think this
can be improved in the future.
For now, you can explicitly set the {{RowTypeInfo}} to retain the field names.
This should work:
{code:scala}
val t1Stream = t1.toAppendStream[Row](t1.getSchema.toRowType)
// t1 stream schema: Row(a: Integer, b: Integer)
println(s"t1 stream schema: ${t1Stream.getType()}")
tEnv.registerDataStream("t1", t1Stream)
/*
new t1 table schema: root
|-- a: INT
|-- b: INT
*/
println(s"new t1 table schema: ${tEnv.scan("t1").getSchema}")
{code}
> Retain the column name when converting a Table to a DataStream
> --------------------------------------------------------------
>
> Key: FLINK-18782
> URL: https://issues.apache.org/jira/browse/FLINK-18782
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Planner
> Affects Versions: 1.9.1
> Reporter: Ying Z
> Priority: Major
>
> mail:
> [http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/How-to-retain-the-column-name-when-convert-a-Table-to-DataStream-td37002.html]
>
> I met some field name errors when try to convert in Table and DataStream.
> First, init a datastream and convert to table 'source', register a
> tablefunction named 'foo'
> {code:java}
> val sourceStream = env.socketTextStream("127.0.0.1", 8010)
> .map(line => line.toInt)
> tableEnv.registerDataStream("source_table", sourceStream, 'a)
> class Foo() extends TableFunction[(Int)] {
> def eval(col: Int): Unit = collect((col * 10))
> }
> tableEnv.registerFunction("foo", new Foo)
> {code}
> Then, use sqlQuery to generate a new table t1 with columns 'a' 'b'
> {code:java}
> val t1 = tableEnv.sqlQuery(
> """
> |SELECT source_table.a, b FROM source_table
> |, LATERAL TABLE(foo(a)) as T(b)
> |""".stripMargin
> )
> /*
> t1 table schema: root
> |-- a: INT
> |-- b: INT
> */
> println(s"t1 table schema: ${t1.getSchema}")
> {code}
> When I try to convert 't1' to a datastream then register to a new table(for
> some reason) named 't1', the columns changes to 'a' 'f0', not 'a' 'b'
> {code:java}
> val t1Stream = t1.toAppendStream[Row]
> // t1 stream schema: Row(a: Integer, f0: Integer)
> println(s"t1 stream schema: ${t1Stream.getType()}")
> tableEnv.registerDataStream("t1", t1Stream)
> /*
> new t1 table schema: root
> |-- a: INT
> |-- f0: INT
> */
> println(s"new t1 table schema: ${tableEnv.scan("t1").getSchema}")
> {code}
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