[FLINK-4244] Field names for union operator do not have to be equal

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.1.0
• Fix Version/s: 1.1.0
• Component/s: Table SQL / API
• Assignee: Jark Wu
• Reporter: Till Rohrmann
• Created: 21/Jul/16 14:06
• Updated: 13/Apr/21 20:40
• Resolved: 25/Jul/16 13:50

Description

Flink Table API's documentation says that the schemas of unioned tables have to be identical (wrt types and names). However, union works also with tables where the types are identical but not the names:

val input1Seq = 0 until 10 map {x => (x, ('a' + x).toChar.toString, x.toDouble)}
    val input2Seq = 0 until 10 map {x => (x, ('a' + x).toChar.toString, x.toDouble)}

    val inputDS1 = env.fromCollection(input1Seq)
    val inputDS2 = env.fromCollection(input2Seq)

    val input1 = tblEnv.fromDataSet(inputDS1, 'a, 'b, 'c)
    tblEnv.registerTable("foobar", input1)
    val input2 = tblEnv.fromDataSet(inputDS2, 'd, 'e, 'f)
    tblEnv.registerTable("foobar2", input2)

    val result = tblEnv.sql("SELECT * FROM foobar UNION ALL SELECT * FROM foobar2")

    tblEnv.toDataSet[Row](result).print()

We should update the documentation accordingly.

Issue Links

• links to: GitHub Pull Request #2280