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From "jiraposter@reviews.apache.org (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-1512) Coprocessors: Support aggregate functions
Date Fri, 15 Apr 2011 06:13:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13020202#comment-13020202
] 

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/#review469
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/src/main/java/org/apache/hadoop/hbase/client/coprocessor/LongColumnInterpreter.java
<https://reviews.apache.org/r/585/#comment914>

    sure



/src/main/java/org/apache/hadoop/hbase/client/coprocessor/LongColumnInterpreter.java
<https://reviews.apache.org/r/585/#comment913>

    As per the current usage, it is one instance per thread. This method is called from the
concrete coprocessor implementation deployed at region level. Though this instance is a singleton,
but its a stateless, hence threadsafe. 
    I can change it to AtomicLong if you say so.



/src/main/java/org/apache/hadoop/hbase/client/coprocessor/LongColumnInterpreter.java
<https://reviews.apache.org/r/585/#comment919>

    As this class implements Writable, it is handled by HBaseObjectWritable such that it writes
its full class name onto the stream (and goes while reading it at server side). Since this
is a stateless, I don't have anything to read write as such. 
    No need to call super.



/src/main/java/org/apache/hadoop/hbase/coprocessor/AggregateCpProtocol.java
<https://reviews.apache.org/r/585/#comment922>

    Ok. Will do all the formatting changes.


- himanshu


On 2011-04-13 08:37:14, Ted Yu wrote:
bq.  
bq.  -----------------------------------------------------------
bq.  This is an automatically generated e-mail. To reply, visit:
bq.  https://reviews.apache.org/r/585/
bq.  -----------------------------------------------------------
bq.  
bq.  (Updated 2011-04-13 08:37:14)
bq.  
bq.  
bq.  Review request for hbase and Gary Helmling.
bq.  
bq.  
bq.  Summary
bq.  -------
bq.  
bq.  This patch provides reference implementation for aggregate function support through Coprocessor
framework.
bq.  ColumnInterpreter interface allows client to specify how the value's byte array is interpreted.
bq.  Some of the thoughts are summarized at http://zhihongyu.blogspot.com/2011/03/genericizing-endpointcoprocessor.html
bq.  
bq.  Himanshu Vashishtha started the work. I provided some review comments and some of the
code.
bq.  
bq.  
bq.  This addresses bug HBASE-1512.
bq.      https://issues.apache.org/jira/browse/HBASE-1512
bq.  
bq.  
bq.  Diffs
bq.  -----
bq.  
bq.    /src/main/java/org/apache/hadoop/hbase/client/coprocessor/AggregationClient.java PRE-CREATION

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

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

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

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

bq.  
bq.  Diff: https://reviews.apache.org/r/585/diff
bq.  
bq.  
bq.  Testing
bq.  -------
bq.  
bq.  TestAggFunctions passes.
bq.  
bq.  
bq.  Thanks,
bq.  
bq.  Ted
bq.  
bq.



> 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-1512-5.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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