> > Hi Tugdual, > Thanks for the response
> 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. > It is not true, it is by default generated and use the timestamp that is part of the ObjectID in many use case (this give me an idea on an UDF for mongo) Also developer can set it when needed, and since it is used as PK it is often use for lookup in apps ( it is true in the context of analytics it is less useful). > However, if users select _id field (cases where users using _id as key) > drill returns its value. > > So yes I can do a projection select _id .... but select _id, * ... does not work so I need to specify the full list of field. (Will see where it is coming from) Anyway it is not a blocking issue at all since we can access it, I was just surprised that it was removed/hidden by default. regards Tug > > On Thu, Jul 16, 2015 at 5:53 PM, Tugdual Grall <[email protected]> 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. >
