[FLINK-9484] Improve generic type inference for User-Defined Functions

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Component/s: Table SQL / API
• Assignee: Rong Rong
• Reporter: Rong Rong
• Created: 01/Jun/18 00:47
• Updated: 30/Apr/21 03:52
• Resolved: 30/Apr/21 03:52

Description

User-defined function has been a great extension for Flink SQL API to support much complex logics.
We experienced many inconvenience when dealing with UDF with generic types and are summarized in the following doc.

Detail implementation plans are listed in sub-tasks for the generic type inference / functioncatalog look up.

In discussion topic: Can we optimize codegen while provide flexibility for output type generic, by the method in FLINK-9430 to chaining: generic result type UDF function with CAST operator.
Initial thought here is to add an logical plan optimizer rule to create a UDFGenericResultTypeCast operator.

Issue Links

• relates to: FLINK-10019 singleton row type objects returned from sub query cannot be chained with other operators
• relates to: FLINK-9430 Support Casting of Object to Primitive types for Flink SQL UDF
• mentioned in: Page Loading...

Sub-Tasks

• Improve type inference for UDFs with composite parameter or result type: Resolved
• Allow Object or Wildcard type in user-define functions as parameter types but not result types: Resolved
• Use generic parameter search for user-define functions when argument contains Object type: Resolved