dongjoon-hyun edited a comment on issue #27233: [SPARK-29701][SQL] Correct behaviours of group analytical queries when empty input given URL: https://github.com/apache/spark/pull/27233#issuecomment-578350299 When you do `SELECT` query, how do you feel if you get a result set with one missing row always? > To me correctness means you get the wrong data back out For the following statement, do you feel the following query is counter-intuitive? SQL should return `0` for `COUNT(*)` when there is no rows. If you feel that's correct, why not on `GROUPING SET grand total`? > the 0 to me seems counter intuitive anyway ``` spark-sql> select sum(a), count(*) from (select 1 a where false); NULL 0 ``` We are discussing now because of the following. > If there are other people that disagree then it obviously needs discussion, `GROUPING SETS` is a commonly used expression for analytics queries (including AB testings). You may not hit this query if your workload doesn't like that. I understand your situation, but please don't overlook the other people situation. We have queries. > if someone can give me a concrete example that this caused them $$ lost that might change my mind. For $$, as you see in this PR, by definition, if Spark doesn't give a `grand total`, we need to run another separate query to get the value in this step. It means we need to check whether the grand total row exists or not and maintain a full complex query for this one missing `() /*grand total*/`. It's a maintenance cost. (I'll not argue about the computing resource cost because the current implementation of this PR is not optimized yet.)
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