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https://issues.apache.org/jira/browse/HBASE-3855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13079633#comment-13079633
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Andrew Purtell commented on HBASE-3855:
---------------------------------------
I have tracked down occasionally failing TestHRegion tests on 0.90 branch to
this commit:
{noformat}
commit 4f4edbaa043952715d4eb9a40605154c6e41d179
Author: Michael Stack <[email protected]>
Date: Fri Jun 10 19:21:41 2011 +0000
HBASE-3855 Performance degradation of memstore because reseek is linear
git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.90@1134419 13f
{noformat}
Perhaps 1 out of 25 test runs fail on my dev laptop.
The same problem may exist on trunk, but I have not checked yet for evidence of
that.
Failures are like:
{quote}
Tests run: 54, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 10.186 sec <<<
FAILURE!
testWritesWhileGetting(org.apache.hadoop.hbase.regionserver.TestHRegion) Time
elapsed: 0.187 sec <<< FAILURE!
junit.framework.AssertionFailedError: expected:<\x00\x00\x006> but
was:<\x00\x00\x004>
at
org.apache.hadoop.hbase.HBaseTestCase.assertEquals(HBaseTestCase.java:685)
at
org.apache.hadoop.hbase.regionserver.TestHRegion.testWritesWhileGetting(TestHRegion.java:2711)
{quote}
> Performance degradation of memstore because reseek is linear
> ------------------------------------------------------------
>
> Key: HBASE-3855
> URL: https://issues.apache.org/jira/browse/HBASE-3855
> Project: HBase
> Issue Type: Improvement
> Reporter: dhruba borthakur
> Priority: Blocker
> Fix For: 0.92.0
>
> Attachments: memstoreReseek.txt, memstoreReseek2.txt
>
>
> The scanner use reseek to find the next row (or next column) as part of a
> scan. The reseek code iterates over a Set to position itself at the right
> place. If there are many thousands of kvs that need to be skipped over, then
> the time-cost is very high. In this case, a seek would be far lesser in cost
> than a reseek.
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