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https://issues.apache.org/jira/browse/HBASE-4435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13478351#comment-13478351
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Ted Yu commented on HBASE-4435:
-------------------------------
I didn't find any test in the patch. It would be difficult for a feature to be
accepted without new tests.
Should GroupByStatsValues be named GroupByStats (since stats imply some values)
?
{code}
+ * Copyright 2012 The Apache Software Foundation
{code}
The above line is no longer needed in license header.
BigDecimalColumnInterpreter is covered in HBASE-6669. To make the workload
reasonable for this JIRA, you can exclude it from patch.
{code}
+public class CharacterColumnInterpreter implements
ColumnInterpreter<Character, Character> {
{code}
Add annotation for audience and stability for public classes.
In GroupByClient.java, the following import can be removed:
{code}
+import com.sun.istack.logging.Logger;
{code}
{code}
+ Map<Text, GroupByStatsValues<T, S>> getStats(
+ final byte[] tableName, final Scan scan,
+ final List<byte [][]> groupByTuples, final byte[][] statsTuple,
{code}
The @param for the above method doesn't match actual parameters - probably you
changed API in later iteration.
{code}
+ class RowNumCallback implements
{code}
The above class can be made private.
I think we should find a better name for the above class - it does aggregation.
{code}
+ long bt = System.currentTimeMillis();
{code}
Please use EnvironmentEdge instead.
{code}
+ table.close();
{code}
Please enclose the above in finally clause.
> 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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