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From Kamesh <kamesh.had...@gmail.com>
Subject Re: [storage engine plugin] How to push down sort/order by to the storage engine?
Date Thu, 16 Jul 2015 15:00:35 GMT
Hi Tugdual,
 The only reason for removing _id field from select * is, in most of the
cases value of _id field generated by Mongo system and users normally do
not use. However, if users select _id field (cases where users using _id as
key) drill returns its value.



On Thu, Jul 16, 2015 at 5:53 PM, Tugdual Grall <tugdual@gmail.com> wrote:

> Hello,
>
> I would like to push down the ORDER BY to the MongoDB database itself ( see
> https://issues.apache.org/jira/browse/DRILL-3165 )
>
> I have looked into the Optimizer, Record Reader and Scan, I do not see how
> I can get the "Order by" clause information from the context.
>
> I see how the filters and projection are used.
>
> Any clue?
>
>
> PS: another side question about Projection & MongoDB:
>    Any reason why the _id is by default removed from the "select * from
> collection" ?
>
>
>
> Regards
> Tug
> @tgrall
>



-- 
Kamesh.

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