[GitHub] [spark] cloud-fan commented on pull request #29540: [SPARK-32698][SQL] Do not fall back to default parallelism if the minimum number of coalesced partitions is not set in AQE

[GitBox <gi...@apache.org>]

cloud-fan commented on pull request #29540:
URL: https://github.com/apache/spark/pull/29540#issuecomment-681693325


   The fallback is there to avoid perf regression with AQE when only a single query runs on the cluster (the benchmark case). I agree it's not ideal for the common cases, but you can set the min size to 1 to disable the fallback easily.
   
   That said, I think it's safer to have this fallback to avoid perf regression (it won't be worse than AQE off), and you can choose to disable it easily to make it more ideal. Maybe the best we can do is to document it in the AQE user guide.
   
   cc @JkSelf @maryannxue 


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