zinking commented on PR #37083:
URL: https://github.com/apache/spark/pull/37083#issuecomment-1193498331

   > > BTW, with CBO off, where do we use row count?
   > 
   > we use it in places like :
   > 
   > 
https://github.com/apache/spark/blob/161c596cafea9c235b5c918d8999c085401d73a9/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/statsEstimation/SizeInBytesOnlyStatsPlanVisitor.scala#L93-L100
   > 
   > where we just multiply row-count with row size. We also use it for BF to 
create 
[bloomFilterAgg](https://github.com/apache/spark/blob/13882bd7b80cd89fc4c58bd96a5ef783a0744019/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/InjectRuntimeFilter.scala#L78-L84).
 In v1 scenario in case of [logical relation 
row-count](https://github.com/apache/spark/blob/161c596cafea9c235b5c918d8999c085401d73a9/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/LogicalRelation.scala#L43-L45)
 can seep in from catalog stats but as you correctly pointed out it has a has a 
chance of `row-count` getting lost in places where we assume we only have 
sizeInBytes for example here :
   > 
   > 
https://github.com/apache/spark/blob/161c596cafea9c235b5c918d8999c085401d73a9/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/statsEstimation/SizeInBytesOnlyStatsPlanVisitor.scala#L54-L58
   
   thought these stats are available in AQE and more accurate though


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