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From "Ted Dunning (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-20) Limit Operator Reference Implementation
Date Fri, 25 Jan 2013 21:47:14 GMT

    [ https://issues.apache.org/jira/browse/DRILL-20?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13563074#comment-13563074
] 

Ted Dunning commented on DRILL-20:
----------------------------------

The BigQuery guys point out that the intent of limit is often really just TOP and that it
is useful to provide a TOP aggregator that is clearly marked as approximate rather than requiring
a fairly subtle optimization of sort + limit.  The same applies for count(distinct).

For both of these, the biggest and strongest argument in my mind is the fact that approximate
algorithms are incredibly efficient but it really is nice if sort+limit or count(distinct)
produce exact results.  TOP and UNIQUES provide a very useful way for users to indicate that
approximate results are acceptable.

                
> Limit Operator Reference Implementation
> ---------------------------------------
>
>                 Key: DRILL-20
>                 URL: https://issues.apache.org/jira/browse/DRILL-20
>             Project: Apache Drill
>          Issue Type: Improvement
>            Reporter: Chris Merrick
>         Attachments: limit-reference.patch
>
>
> Build off of Jacques work on reference implementations - the limit operator.

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