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From "James Taylor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-4686) Phoenix stats does not account for server side limit push downs
Date Thu, 19 Apr 2018 07:36:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16443655#comment-16443655
] 

James Taylor commented on PHOENIX-4686:
---------------------------------------

Thanks for the wip patch, [~abhishek.chouhan]. I'd recommend following the same pattern that
we have for point lookups. Just let the existing code execute as-is (we need it to calculate
the scans anyway), and then at the end (if we're pushing a PageFilter, or we could detect
it based on the QueryPlan as well), just multiple the row size estimate by the limit to calculate
the estimated bytes scanned. Also, I think we might need a new ExplainPlan attribute like
EST_BASED_ON_STATS which is set to false in this case and in the case of point lookups (since
in neither case would we be relying on stats for the estimate). The reason this is useful
is that in these cases, the EST_INFO_TS being null can be ignored by the client.

> Phoenix stats does not account for server side limit push downs
> ---------------------------------------------------------------
>
>                 Key: PHOENIX-4686
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4686
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: Abhishek Singh Chouhan
>            Assignee: Abhishek Singh Chouhan
>            Priority: Major
>         Attachments: PHOENIX-4686-wip.master.patch
>
>
> For a query like SELECT * FROM FOO LIMIT 10 the EST_BYTES_READ does not take into account
a limit correctly when there's no WHERE clause (or a WHERE clause that gets compiled out into
start/stop row key on the scan).



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