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From "jiraposter@reviews.apache.org (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-1512) Coprocessors: Support aggregate functions
Date Tue, 12 Apr 2011 02:31:06 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13018677#comment-13018677
] 

jiraposter@reviews.apache.org commented on HBASE-1512:
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/585/
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Review request for hbase and Gary Helmling.


Summary
-------

This patch provides reference implementation for aggregate function support through Coprocessor
framework.
ColumnInterpreter interface allows client to specify how the value's byte array is interpreted.
Some of the thoughts are summarized at http://zhihongyu.blogspot.com/2011/03/genericizing-endpointcoprocessor.html

Himanshu Vashishtha started the work. I provided some review comments and some of the code.


This addresses bug HBASE-1512.
    https://issues.apache.org/jira/browse/HBASE-1512


Diffs
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  /src/main/java/org/apache/hadoop/hbase/client/coprocessor/AggregationClient.java PRE-CREATION

  /src/main/java/org/apache/hadoop/hbase/client/coprocessor/LongColumnInterpreter.java PRE-CREATION

  /src/main/java/org/apache/hadoop/hbase/coprocessor/AggregateCpProtocol.java PRE-CREATION

  /src/main/java/org/apache/hadoop/hbase/coprocessor/AggregateProtocolImpl.java PRE-CREATION

  /src/main/java/org/apache/hadoop/hbase/coprocessor/ColumnInterpreter.java PRE-CREATION 
  /src/test/java/org/apache/hadoop/hbase/coprocessor/TestAggFunctions.java PRE-CREATION 

Diff: https://reviews.apache.org/r/585/diff


Testing
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TestAggFunctions passes.


Thanks,

Ted



> Coprocessors: Support aggregate functions
> -----------------------------------------
>
>                 Key: HBASE-1512
>                 URL: https://issues.apache.org/jira/browse/HBASE-1512
>             Project: HBase
>          Issue Type: Sub-task
>          Components: coprocessors
>            Reporter: stack
>         Attachments: 1512.zip, AggregateCpProtocol.java, AggregateProtocolImpl.java,
AggregationClient.java, ColumnInterpreter.java, patch-1512-2.txt, patch-1512-3.txt, patch-1512-4.txt,
patch-1512.txt
>
>
> 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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