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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-19416) Create single version transactional table metastore statistics for aggregation queries
Date Tue, 12 Jun 2018 21:48:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-19416?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16510260#comment-16510260
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Sergey Shelukhin commented on HIVE-19416:
-----------------------------------------

Looking at the patch now, not done reviewing yet, I post the comments in increments.
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
txns/validIdlists.
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 items.


> 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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