[FLINK-34258] Incorrect example of accumulator usage within emitUpdateWithRetract for TableAggregateFunction

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.19.0, 1.18.1
• Fix Version/s: 1.19.0
• Component/s: Documentation, Table SQL / API
• Labels: pull-request-available
• Assignee: Jane Chan
• Reporter: Jane Chan
• Created: 29/Jan/24 07:30
• Updated: 02/Feb/24 02:12
• Resolved: 02/Feb/24 02:11

Description

The documentation provides an example of using `emitUpdateWithRetract`. However, the example is misleading as it incorrectly suggests that the accumulator can be updated within the `emitUpdateWithRetract method`. In reality, the order of invocation is to first call `getAccumulator` and then `emitUpdateWithRetract`, which means that updating the accumulator within `emitUpdateWithRetract` will not take effect. Please see GroupTableAggFunction#L141 ~ GroupTableAggFunction#L146 for more details.

Issue Links

• Discovered while testing: FLINK-31788 Add back Support emitValueWithRetract for TableAggregateFunction
• links to: GitHub Pull Request #24215