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From "Maryann Xue (JIRA)" <>
Subject [jira] [Updated] (PHOENIX-136) Support derived tables in from clause
Date Thu, 14 Aug 2014 03:10:11 GMT


Maryann Xue updated PHOENIX-136:

    Summary: Support derived tables in from clause  (was: Support derived tables)

> Support derived tables in from clause
> -------------------------------------
>                 Key: PHOENIX-136
>                 URL:
>             Project: Phoenix
>          Issue Type: Task
>            Reporter: James Taylor
>            Assignee: Maryann Xue
>              Labels: enhancement
>             Fix For: 5.0.0, 3.1, 4.1
> Add support for derived queries of the form:
> SELECT * FROM ( SELECT company, revenue FROM Company ORDER BY revenue) LIMIT 10
> Adding support for this requires a compile time change as well as a runtime execution
change. The first version of the compile-time change could limit aggregation to only be allowed
in the inner or the outer query, but not both. In this case, the inner and outer queries can
be combined into a single query with the outer select becoming just a remapping of a subset
of the projection from the inner select. The second version of the compile-time change could
handle aggregation in the inner and outer select by performing client side (this is likely
a less common scenario).
> For the runtime execution, change the UngroupedAggregateRegionObserver would be modified
to look for a new "TopNLimit" attribute with an int value in the Scan. This would control
the maximum number of values for the coprocessor to hold on to as the scan is performed. Then
the GroupedAggregatingResultIterator would be modified to handle keeping the topN values received
back from all the child iterators.

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