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https://issues.apache.org/jira/browse/PHOENIX-136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13976377#comment-13976377
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ASF GitHub Bot commented on PHOENIX-136:
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Github user JamesRTaylor commented on the pull request:
https://github.com/apache/incubator-phoenix/pull/31#issuecomment-41003342
+1. This is fantastic, @maryannxue! Let's file separate JIRAs for each type
of query that's not yet supported. The list is getting smaller!
> Support derived tables
> ----------------------
>
> Key: PHOENIX-136
> URL: https://issues.apache.org/jira/browse/PHOENIX-136
> Project: Phoenix
> Issue Type: Task
> Reporter: James Taylor
> Assignee: James Taylor
> Labels: enhancement
>
> 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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