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From "Chris Merrick (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-20) Limit Operator Reference Implementation
Date Thu, 24 Jan 2013 04:19:14 GMT

    [ https://issues.apache.org/jira/browse/DRILL-20?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13561414#comment-13561414
] 

Chris Merrick commented on DRILL-20:
------------------------------------

Interesting idea, I think I do understand the end result you're going after.  This feature
also means that you could have multiple limits, right?  And therefore conflicting limits?


I did some research and the only other existing query language I could find with a similar
concept is BigQuery, where it looks like you might be able to accomplish this with a combination
of the TOP() operator and a WITHIN clause - although it's not clear from the docs whether
that's legal.  It's also very clear in the docs that the TOP operator is implemented differently
than a regular LIMIT.

BigQuery's actual LIMIT operator seems to be restricted to only applying to the top-level
records.

Not that the goal is to necessarily copy BigQuery exactly, but it seems like they went about
this in a different way.  Was there any query language in particular that motivated you to
add this?  I'm mostly just trying to get some insight into how you all are thinking about
the language design - overall I do think this makes sense, but it has a few subtle complications.
                
> 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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