Fabian Hueske created FLINK-9419:
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Summary: 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
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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