[FLINK-18683] Support @DataTypeHint for TableFunction output types

• Type: Sub-task
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 1.12.0
• Component/s: Table SQL / API
• Labels: pull-request-available
• Assignee: Timo Walther
• Reporter: Fabian Hueske
• Created: 23/Jul/20 10:20
• Updated: 01/Sep/20 13:15
• Resolved: 01/Sep/20 13:15

Description

For ScalarFunctions, the return type of an eval method can be declared with a @DataTypeHint:

@DataTypeHint("INT")
public Integer eval(Integer value) {
  return value * 2;
}

This does not work for TableFunctions because the @DataTypeHint annotation refers to the void return type. Hence, TableFunction eval() methods must always be annotated with the more complex @FunctionHint method.
However, I think that context, it is clear that the @DataTypeHint annotation refers to the actual return type of the table function (the type parameter of TableFunction<OUT>).

We could consider allowing @DataTypeHint annotations also on TableFunction classes (defining the output type of all eval methods) and eval() methods.

Issue Links

• links to: GitHub Pull Request #13149