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Posted to issues@hbase.apache.org by "Anoop Sam John (JIRA)" <ji...@apache.org> on 2012/12/29 12:24:15 UTC
[jira] [Commented] (HBASE-4435) Add Group By functionality using
Coprocessors
[ https://issues.apache.org/jira/browse/HBASE-4435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13540856#comment-13540856 ]
Anoop Sam John commented on HBASE-4435:
---------------------------------------
May be good to add to the CP examples section. Someone working with this?
> 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
> Labels: by, coprocessors, group, hbase
> Attachments: HBase-4435.patch, HBASE-4435-v2.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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