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https://issues.apache.org/jira/browse/HBASE-1512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12903275#action_12903275
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Mingjie Lai commented on HBASE-1512:
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Hi Himanshu.
Right now I'm doing some cleanups for coprocessor. Here is the code:
http://github.com/mlai/hbase. Please use the branch -- coprocessors_mlai.
However our current objective is to utilize CP to implement role based access
control(RBAC) toward 0.90. We only need Coprocessor, RegionObservor,
CommandType interfaces for this purpose. So I didn't include the MapReduce and
FilterInterface in the branch (neither for 0.90 I think).
You can take a look at that branch. It can pass all HBase test cases, but we
still need to improve it a little for exception handling.
If you have interests for Mapreduce implementation, you can also refer the
first patch of HBASE-2001.
Thanks,
Mingjie
> Coprocessors: Support aggregate functions
> -----------------------------------------
>
> Key: HBASE-1512
> URL: https://issues.apache.org/jira/browse/HBASE-1512
> Project: HBase
> Issue Type: Sub-task
> Reporter: stack
>
> Chatting with jgray and holstad at the kitchen table about counts, sums, and
> other aggregating facility, facility generally where you want to calculate
> some meta info on your table, it seems like it wouldn't be too hard making a
> filter type that could run a function server-side and return the result ONLY
> of the aggregation or whatever.
> For example, say you just want to count rows, currently you scan, server
> returns all data to client and count is done by client counting up row keys.
> A bunch of time and resources have been wasted returning data that we're not
> interested in. With this new filter type, the counting would be done
> server-side and then it would make up a new result that was the count only
> (kinda like mysql when you ask it to count, it returns a 'table' with a count
> column whose value is count of rows). We could have it so the count was
> just done per region and return that. Or we could maybe make a small change
> in scanner too so that it aggregated the per-region counts.
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