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https://issues.apache.org/jira/browse/FLINK-9419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16487523#comment-16487523
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Hequn Cheng commented on FLINK-9419:
------------------------------------
Hi, [~fhueske], same problem as
[FLINK-8566|https://issues.apache.org/jira/browse/FLINK-8566] and
[FLINK-8594|https://issues.apache.org/jira/browse/FLINK-8594]. I will start to
solve this problem when the stream-stream joins are done.
> UNION should not be treated as retraction producing operator
> ------------------------------------------------------------
>
> Key: FLINK-9419
> URL: https://issues.apache.org/jira/browse/FLINK-9419
> Project: Flink
> Issue Type: Bug
> Components: Table API & SQL
> Reporter: Fabian Hueske
> Assignee: Hequn Cheng
> Priority: Major
>
> The following query fails
> {code}
> SELECT
> user_id,
> count(msg),
> HOP_END(rowtime, INTERVAL '1' second, INTERVAL '1' minute)
> FROM (SELECT rowtime, user_id, action_name AS msg FROM
> event_client_action
> WHERE /* various clauses */
> UNION SELECT rowtime, user_id, action_type AS msg FROM
> event_server_action
> WHERE /* various clauses */
> )
> GROUP BY
> HOP(rowtime, INTERVAL '1' second, INTERVAL '1' minute), user_id
> {code}
> with
> {quote}Retraction on windowed GroupBy aggregation is not supported yet. Note:
> Windowed GroupBy aggregation should not follow a non-windowed GroupBy
> aggregation.{quote}
> The problem is that the {{UNION}} operator is translated into a {{UNION ALL}}
> and a subsequent {{GROUP BY}} on all attributes without an aggregation
> function. Currently, all {{GROUP BY}} operators are treated as
> retraction-producing operators. However, this is only true for grouping
> operators with aggregation functions. If the operator groups on all
> attributes and has no aggregation functions, it does not produce retractions
> but only forwards them (similar to a filter operator).
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