[FLINK-20110] Support 'merge' method for first_value and last_value UDAF

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.12.0
• Fix Version/s: 1.20.0
• Component/s: Table SQL / Runtime
• Labels: auto-unassigned pull-request-available
• Assignee: Unassigned
• Reporter: hailong wang
• Created: 12/Nov/20 13:05
• Updated: 11/Mar/24 12:44

Description

From the user-zh email, when use first_value function in hop window, It throws the exception because first_vaue does not implement the merge method.
We can support 'merge' method for first_value and last_value UDAF

Issue Links

• duplicates: FLINK-20440 `LAST_VALUE` aggregate function can not be used in hop window
• relates to: FLINK-24664 Support merge for JSON_ARRAYAGG
• links to: GitHub Pull Request #14280