AngersZhuuuu commented on issue #26437: [SPARK-29800][SQL] Plan non-correlated Exists 's subquery in PlanSubqueries URL: https://github.com/apache/spark/pull/26437#issuecomment-558463297 > @AngersZhuuuu after some more thoughts, I think we can still reuse non-correlated scalar subquery. We can rewrite `WHERE EXISTS (subquery)` to `WHERE (SELECT 1 FROM (subquery) LIMIT 1) IS NOT NULL`. > > What do you think? It's not semantically straightforward, and the overhead is the same as what you said before？ `limit 1` is not most efficient. I don't know if my understanding is wrong....
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