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From "Pengcheng Xiong (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-11471) Expose query cost estimates (from CBO?) in explain plan
Date Wed, 05 Aug 2015 21:19:04 GMT

    [ https://issues.apache.org/jira/browse/HIVE-11471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14658959#comment-14658959
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Pengcheng Xiong commented on HIVE-11471:
----------------------------------------

[~hagleitn], i am not sure, but I guess [~sershe] is asking the cost (cardinality) of a query
plan that is specified by the user. If that is the case, i think the user can just turn off
CBO and give Hive a query and run explain, it will show the cost. For example, the plan that
is given by CBO for a query which joins A,B,C tables is A join B and then join C. The user
can turn off CBO and write the query like A join C join B, then run explain will show the
cost and the plan. The user can compare it with the plan that is given by CBO.

> Expose query cost estimates (from CBO?) in explain plan
> -------------------------------------------------------
>
>                 Key: HIVE-11471
>                 URL: https://issues.apache.org/jira/browse/HIVE-11471
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Sergey Shelukhin
>
> Some users of Hive suggested that it would be useful to see abstract cost of the query
plan in explain, so that different manual rewrites of the query could be compared before running.




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