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https://issues.apache.org/jira/browse/FLINK-40976?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated FLINK-40976:
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Labels: pull-request-available (was: )
> JoinToMultiJoinForReorderRule applies a post-join filter twice when merging
> joins for reorder
> ---------------------------------------------------------------------------------------------
>
> Key: FLINK-40976
> URL: https://issues.apache.org/jira/browse/FLINK-40976
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Planner
> Reporter: Hanyu Zheng
> Priority: Major
> Labels: pull-request-available
>
> In batch mode with \{{table.optimizer.join-reorder-enabled = true}}, a filter
> on the null-generating side of an outer join is applied a second time above
> that outer join after JoinToMultiJoinForReorderRule merges the joins. Rows
> that should come back with NULLs are removed. The rule runs before both
> reorder strategies (bushy and LOPT), so both are affected.
> h3. Reproduction
> {code:sql}
> SET 'execution.runtime-mode' = 'batch';
> SET 'table.optimizer.join-reorder-enabled' = 'true';
> SELECT * FROM T1 LEFT JOIN
> (SELECT * FROM T2 LEFT JOIN T3 ON a2 = a3 WHERE COALESCE(b3, b2) > 3) v
> ON a1 = a2;
> {code}
> Expected: every T1 row, with NULLs where v has no match. Actual: T1 rows
> without a match in v are missing, because \{{COALESCE(b3, b2) > 3}} is
> applied again above the outer LEFT JOIN. With join reorder disabled, the
> result is correct.
> h3. Workaround
> Disable \{{table.optimizer.join-reorder-enabled}}.
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