paul-rogers commented on PR #13201:
URL: https://github.com/apache/druid/pull/13201#issuecomment-1281125606

   @rohangarg, thanks for the explanation about the cutoff quantity. That 
raises another question: how do we know the number? If a join is against an 
entire table, one can just look at the table cardinality (the sum of the row 
counts across all segments). If there is a filter on a table, estimating the 
post-filter row count is a difficult challenge -- one that all query planners 
wrestle with (and for which Calcite provides a cost-based algorithm.) Is this 
PR only considering the entire table cardinality? 


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