calvinchengx commented on issue #24044:
URL: https://github.com/apache/datafusion/issues/24044#issuecomment-5229014416

   @alamb It's a bug rather than a change in behaviour, but I don't think it 
should hold 55.0.0.
   
   A bug because rows that are already available can be withheld indefinitely: 
the producer-side coalescer flushes its residual only when the input ends, and 
an unbounded input never does. For a source emitting small batches the 
practical effect is no output at all rather than delayed output. In the repro 
above, at the default 8192 and a source producing 10 rows/second, the first 
batch would appear after roughly 14 minutes.
   
   Not a regression in this cycle, though. I checked 52.0.0: the 
`coalesce_batches` optimizer rule there had no boundedness handling either, so 
the external `CoalesceBatchesExec` it inserted after `RepartitionExec` had the 
same blind spot. #18782 moved coalescing inside the operator, which made a 
longstanding gap structural rather than introducing it. So holding the release 
would not be protecting anyone from something newly broken.
   


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