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https://issues.apache.org/jira/browse/FLINK-20840?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17258216#comment-17258216
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Leonard Xu commented on FLINK-20840:
------------------------------------
The rule `FlinkProjectJoinTransposeRule` was added in logical rewrite phase
which uses volcano optimizer, the optimized plan is uncertain for example above
case.
> Projection pushdown doesn't work in temporal(lookup) join
> ----------------------------------------------------------
>
> Key: FLINK-20840
> URL: https://issues.apache.org/jira/browse/FLINK-20840
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Planner
> Affects Versions: 1.12.0
> Reporter: Leonard Xu
> Priority: Major
>
> {code:java}
> sql 1:
> |SELECT T.*, D.id
> |FROM MyTable AS T
> |JOIN LookupTable FOR SYSTEM_TIME AS OF T.proctime AS D
> |ON T.a = D.id
> optmized plan:
> Calc(select=[a, b, c, PROCTIME_MATERIALIZE(proctime) AS proctime, rowtime,
> id])
> +- LookupJoin(table=[default_catalog.default_database.LookupTable],
> joinType=[InnerJoin], async=[false], lookup=[id=a], select=[a, b, c,
> proctime, rowtime, id, name, age])
> +- DataStreamScan(table=[[default_catalog, default_database, MyTable]],
> fields=[a, b, c, proctime, rowtime])
> sql 2:
> |SELECT T.a, D.id
> |FROM MyTable AS T
> |JOIN LookupTable FOR SYSTEM_TIME AS OF T.proctime AS D
> |ON T.a = D.id
> optmized plan:
> LookupJoin(table=[default_catalog.default_database.LookupTable],
> joinType=[InnerJoin], async=[false], lookup=[id=a], select=[a, id])
> +- Calc(select=[a])
> +- DataStreamScan(table=[[default_catalog, default_database, MyTable]],
> fields=[a, b, c, proctime, rowtime])
> {code}
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