[FLINK-18782] Retain the column name when converting a Table to a DataStream

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.9.1
• Component/s: Table SQL / API
• Assignee: Unassigned
• Reporter: Ying Z
• Created: 31/Jul/20 09:58
• Updated: 29/Apr/21 10:11

Description

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'

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)

Then, use sqlQuery to generate a new table t1 with columns 'a' 'b'

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}")

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'

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}")