sesteves commented on issue #22641:
URL: https://github.com/apache/datafusion/issues/22641#issuecomment-5409965836

   One join type appears to be missing from the explicit guard and test scope: 
`JoinType::LeftSemi`.
   
   The current `NestedLoopJoinExec` source comment explicitly groups `LEFT 
SEMI` with `LEFT`, `LEFT ANTI`, and `LEFT MARK` as having the same latent 
multi-partition fallback issue. `need_produce_result_in_final` also includes 
`LeftSemi`.
   
   For `LeftSemi`, the per-partition `JoinLeftData` state can emit the same 
left row from more than one right partition when that row has matches in 
multiple partitions. This is the semi-join form of the same missing 
cross-partition coordination problem.
   
   Could the fallback-disable guard and regression matrix also include 
`JoinType::LeftSemi`?


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