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https://issues.apache.org/jira/browse/HBASE-13374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14396362#comment-14396362
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Hadoop QA commented on HBASE-13374:
-----------------------------------
{color:green}+1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12709477/HBASE-13374-v1.patch
against master branch at commit fef8ae9c70f47d87baa985a66e94d7b90b861f08.
ATTACHMENT ID: 12709477
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:green}+1 tests included{color}. The patch appears to include 4 new
or modified tests.
{color:green}+1 hadoop versions{color}. The patch compiles with all
supported hadoop versions (2.4.1 2.5.2 2.6.0)
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 protoc{color}. The applied patch does not increase the
total number of protoc compiler warnings.
{color:green}+1 javadoc{color}. The javadoc tool did not generate any
warning messages.
{color:green}+1 checkstyle{color}. The applied patch does not increase the
total number of checkstyle errors
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 2.0.3) warnings.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:green}+1 lineLengths{color}. The patch does not introduce lines
longer than 100
{color:green}+1 site{color}. The mvn site goal succeeds with this patch.
{color:green}+1 core tests{color}. The patch passed unit tests in .
Test results:
https://builds.apache.org/job/PreCommit-HBASE-Build/13565//testReport/
Release Findbugs (version 2.0.3) warnings:
https://builds.apache.org/job/PreCommit-HBASE-Build/13565//artifact/patchprocess/newFindbugsWarnings.html
Checkstyle Errors:
https://builds.apache.org/job/PreCommit-HBASE-Build/13565//artifact/patchprocess/checkstyle-aggregate.html
Console output:
https://builds.apache.org/job/PreCommit-HBASE-Build/13565//console
This message is automatically generated.
> Small scanners (with particular configurations) do not return all rows
> ----------------------------------------------------------------------
>
> Key: HBASE-13374
> URL: https://issues.apache.org/jira/browse/HBASE-13374
> Project: HBase
> Issue Type: Bug
> Affects Versions: 1.0.0, 2.0.0, 1.1.0, 0.98.13
> Reporter: Jonathan Lawlor
> Assignee: Jonathan Lawlor
> Priority: Blocker
> Fix For: 2.0.0, 1.0.1, 1.1.0, 0.98.13
>
> Attachments: HBASE-13374-v1.patch, HBASE-13374-v1.patch,
> HBASE-13374-v1.patch, HBASE-13374-v1.patch, HBASE-13374-v1.patch,
> small-scanner-data-loss-tests-0.98.patch,
> small-scanner-data-loss-tests-branch-1.0+.patch
>
>
> I recently ran into a couple data loss issues with small scans. Similar to
> HBASE-13262, these issues only appear when scans are configured in such a way
> that the max result size limit is reached before the caching limit is
> reached. As far as I can tell, this issue affects branches 0.98+
> I should note that after investigation it looks like the root cause of these
> issues is not the same as HBASE-13262. Rather, these issue are caused by
> errors in the small scanner logic (I will explain in more depth below).
> Furthermore, I do know that the solution from HBASE-13262 has not made its
> way into small scanners (it is being addressed in HBASE-13335). As a result I
> made sure to test these issues with the patch from HBASE-13335 applied and I
> saw that they were still present.
> The following two issues have been observed (both lead to data loss):
> 1. When a small scan is configured with a caching value of Integer.MAX_VALUE,
> and a maxResultSize limit that is reached before the region is exhausted,
> integer overflow will occur. This eventually leads to a preemptive skip of
> the regions.
> 2. When a small scan is configured with a maxResultSize that is smaller than
> the size of a single row, the small scanner will jump between regions
> preemptively. This issue seems to be because small scanners assume that,
> unless a region is exhausted, at least 2 rows will be returned from the
> server. This assumption isn't clearly state in the small scanners but is
> implied through the use of {{skipRowOfFirstResult}}.
> Again, I would like to stress that the root cause of these issues is *NOT*
> related to the cause of HBASE-13262. These issues occur because of
> inappropriate assumption made in the small scanner logic. The inappropriate
> assumptions are:
> 1. Integer overflow will not occur when incrementing caching
> 2. At least 2 rows will be returned from the server unless the region has
> been exhausted
> I am attaching a patch that contains tests to display these issues. If these
> issues should be split into separate JIRAs please let me know.
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