[jira] [Created] (FLINK-34258) Incorrect example of accumulator usage within emitUpdateWithRetract for TableAggregateFunction

["Jane Chan (Jira)" <ji...@apache.org>]

Jane Chan created FLINK-34258:
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             Summary: Incorrect example of accumulator usage within emitUpdateWithRetract for TableAggregateFunction
                 Key: FLINK-34258
                 URL: https://issues.apache.org/jira/browse/FLINK-34258
             Project: Flink
          Issue Type: Bug
          Components: Documentation, Table SQL / API
    Affects Versions: 1.18.1, 1.19.0
            Reporter: Jane Chan
            Assignee: Jane Chan


The [documentation|https://nightlies.apache.org/flink/flink-docs-master/docs/dev/table/functions/udfs/#retraction-example] 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|https://github.com/apache/flink/blob/20450485b20cb213b96318b0c3275e42c0300e15/flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/operators/aggregate/GroupTableAggFunction.java#L141] ~ [GroupTableAggFunction#L146|https://github.com/apache/flink/blob/20450485b20cb213b96318b0c3275e42c0300e15/flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/operators/aggregate/GroupTableAggFunction.java#L146] for more details.




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