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https://issues.apache.org/jira/browse/HBASE-29039?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18071973#comment-18071973
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Hudson commented on HBASE-29039:
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Results for branch master
[build #38 on
builds.a.o|https://ci-hbase.apache.org/job/HBase-Integration-Test/job/master/38/]:
(/) *{color:green}+1 overall{color}*
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details (if available):
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> Optimize read performance for accumulated delete markers on the same row or
> cell
> --------------------------------------------------------------------------------
>
> Key: HBASE-29039
> URL: https://issues.apache.org/jira/browse/HBASE-29039
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 2.6.1, 2.5.10
> Reporter: Eungsop Yoo
> Assignee: Junegunn Choi
> Priority: Major
> Labels: pull-request-available
> Fix For: 2.7.0, 3.0.0-beta-2, 2.5.15, 2.6.6
>
> Attachments: screenshot-2.png
>
>
> I have been confronted with a problem that some Get operations take several
> seconds.
> !screenshot-2.png!
> The reason was founded that users Put and Delete on some rows repeatedly. As
> delete markers are accumulated on the same row or cell, Get operations slow
> down. It can be reproduced by follow HBase shell commands.
> {code:java}
> create 'test', 'c'
> java_import org.apache.hadoop.hbase.client.Delete
> java_import org.apache.hadoop.hbase.TableName
> java_import java.lang.System
> con = @hbase.instance_variable_get(:@connection)
> table = con.getTable(TableName.valueOf('test'))
> 1000.times do |i|
> # batch 10000 deletes with different timestamps every 10 seconds
> now = System.currentTimeMillis()
> dels = 10000.times.map do |i|
> del = Delete.new(Bytes.toBytes('row'))
> del.addFamily(Bytes.toBytes('c'), now + i)
> end
> table.delete(dels)
> sleep(10)
> puts "i - #{i}"
> get 'test', 'row'
> end
> {code}
> {code:java}
> i - 0
> COLUMN
> CELL
> 0 row(s)
> Took 0.0251 seconds
> ...
> i - 10
> COLUMN
> CELL
> 0 row(s)
> Took 0.0412 seconds
> ...
> i - 20
> COLUMN
> CELL
> 0 row(s)
> Took 0.0760 seconds
> ...
> i - 30
> COLUMN
> CELL
> 0 row(s)
> Took 0.1014 seconds
> ...
> i - 40
> COLUMN
> CELL
> 0 row(s)
> Took 0.1616 seconds
> ...
> {code}
> But the performance of Get operations can be optimized by using SEEK_NEXT_COL.
> {code:java}
> i - 1
> COLUMN
> CELL
> 0 row(s)
> Took 0.0087 seconds
> ...
> i - 11
> COLUMN
> CELL
> 0 row(s)
> Took 0.0077 seconds
> ...
> i - 21
> COLUMN
> CELL
> 0 row(s)
> Took 0.0087 seconds
> ...
> {code}
> Please review the PR.
> [https://github.com/apache/hbase/pull/6557]
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