Sergey Shelukhin commented on HIVE-19416:

Looking at the patch now, not done reviewing yet, I post the comments in 
My main concern for now is that I don't quite understand why we need two 
mechanisms: first, some alter/add queries remove COLUMN_STATS_ACCURATE on write 
(we also invalidate it in the response on read but that seems to be just the 
communication mechanism), and then in is...Valid... method on read we check 
that parameter. However, in the is...Valid... method, we also check 
Shouldn't just the latter be enough, with no need for the former?
Using parameter as a communication mechanism from metastore to avoid massive QL 
changes looks good to me.

Also there are many TODOs in the patch. I would be nice to clean them up - fix 
simple ones, remove unnecessary ones if any, and make complex ones into work 

> Create single version transactional table metastore statistics for 
> aggregation queries
> --------------------------------------------------------------------------------------
>                 Key: HIVE-19416
>                 URL: https://issues.apache.org/jira/browse/HIVE-19416
>             Project: Hive
>          Issue Type: Bug
>          Components: Transactions
>            Reporter: Steve Yeom
>            Assignee: Steve Yeom
>            Priority: Major
> The system should use only statistics for aggregation queries like count on 
> transactional tables.

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