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From "lifeng (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4435) Add Group By functionality using Coprocessors
Date Tue, 17 Apr 2012 13:19:19 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13255546#comment-13255546
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lifeng commented on HBASE-4435:
-------------------------------

when can this patch be put into hbase?
                
> Add Group By functionality using Coprocessors
> ---------------------------------------------
>
>                 Key: HBASE-4435
>                 URL: https://issues.apache.org/jira/browse/HBASE-4435
>             Project: HBase
>          Issue Type: Improvement
>          Components: coprocessors
>            Reporter: Nichole Treadway
>            Priority: Minor
>         Attachments: HBase-4435.patch
>
>
> Adds in a Group By -like functionality to HBase, using the Coprocessor framework. 
> It provides the ability to group the result set on one or more columns (groupBy families).
It computes statistics (max, min, sum, count, sum of squares, number missing) for a second
column, called the stats column. 
> To use, I've provided two implementations.
> 1. In the first, you specify a single group-by column and a stats field:
>       statsMap = gbc.getStats(tableName, scan, groupByFamily, groupByQualifier, statsFamily,
statsQualifier, statsFieldColumnInterpreter);
> The result is a map with the Group By column value (as a String) to a GroupByStatsValues
object. The GroupByStatsValues object has max,min,sum etc. of the stats column for that group.
> 2. The second implementation allows you to specify a list of group-by columns and a stats
field. The List of group-by columns is expected to contain lists of {column family, qualifier}
pairs. 
>       statsMap = gbc.getStats(tableName, scan, listOfGroupByColumns, statsFamily, statsQualifier,
statsFieldColumnInterpreter);
> The GroupByStatsValues code is adapted from the Solr Stats component.

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