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https://issues.apache.org/jira/browse/HADOOP-5967?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12716864#action_12716864
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Hadoop QA commented on HADOOP-5967:
-----------------------------------
-1 overall. Here are the results of testing the latest attachment
http://issues.apache.org/jira/secure/attachment/12409836/single-mapper.patch
against trunk revision 782083.
+1 @author. The patch does not contain any @author tags.
-1 tests included. The patch doesn't appear to include any new or modified
tests.
Please justify why no tests are needed for this patch.
+1 javadoc. The javadoc tool did not generate any warning messages.
+1 javac. The applied patch does not increase the total number of javac
compiler warnings.
+1 findbugs. The patch does not introduce any new Findbugs warnings.
+1 Eclipse classpath. The patch retains Eclipse classpath integrity.
+1 release audit. The applied patch does not increase the total number of
release audit warnings.
-1 core tests. The patch failed core unit tests.
-1 contrib tests. The patch failed contrib unit tests.
Test results:
http://hudson.zones.apache.org/hudson/job/Hadoop-Patch-vesta.apache.org/472/testReport/
Findbugs warnings:
http://hudson.zones.apache.org/hudson/job/Hadoop-Patch-vesta.apache.org/472/artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Checkstyle results:
http://hudson.zones.apache.org/hudson/job/Hadoop-Patch-vesta.apache.org/472/artifact/trunk/build/test/checkstyle-errors.html
Console output:
http://hudson.zones.apache.org/hudson/job/Hadoop-Patch-vesta.apache.org/472/console
This message is automatically generated.
> Sqoop should only use a single map task
> ---------------------------------------
>
> Key: HADOOP-5967
> URL: https://issues.apache.org/jira/browse/HADOOP-5967
> Project: Hadoop Core
> Issue Type: Improvement
> Reporter: Aaron Kimball
> Assignee: Aaron Kimball
> Priority: Minor
> Attachments: single-mapper.patch
>
>
> The current DBInputFormat implementation uses SELECT ... LIMIT ... OFFSET
> statements to read from a database table. This actually results in several
> queries all accessing the same table at the same time. Most database
> implementations will actually use a full table scan for each such query,
> starting at row 1 and scanning down until the OFFSET is reached before
> emitting data to the client. The upshot of this is that we see O(n^2)
> performance in the size of the table when using a large number of mappers,
> when a single mapper would read through the table in O(n) time in the number
> of rows.
> This patch sets the number of map tasks to 1 in the MapReduce job sqoop
> launches.
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