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https://issues.apache.org/jira/browse/HIVE-9995?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16806755#comment-16806755
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Denys Kuzmenko commented on HIVE-9995:
--------------------------------------
rebased
> ACID compaction tries to compact a single file
> ----------------------------------------------
>
> Key: HIVE-9995
> URL: https://issues.apache.org/jira/browse/HIVE-9995
> Project: Hive
> Issue Type: Bug
> Components: Transactions
> Affects Versions: 1.0.0
> Reporter: Eugene Koifman
> Assignee: Denys Kuzmenko
> Priority: Major
> Attachments: HIVE-9995.01.patch, HIVE-9995.02.patch,
> HIVE-9995.03.patch, HIVE-9995.04.patch, HIVE-9995.05.patch,
> HIVE-9995.06.patch, HIVE-9995.07.patch, HIVE-9995.08.patch,
> HIVE-9995.09.patch, HIVE-9995.WIP.patch
>
>
> Consider TestWorker.minorWithOpenInMiddle()
> since there is an open txnId=23, this doesn't have any meaningful minor
> compaction work to do. The system still tries to compact a single delta file
> for 21-22 id range, and effectively copies the file onto itself.
> This is 1. inefficient and 2. can potentially affect a reader.
> (from a real cluster)
> Suppose we start with
> {noformat}
> drwxr-xr-x - ekoifman staff 0 2016-06-09 16:03
> /user/hive/warehouse/t/base_0000016
> -rw-r--r-- 1 ekoifman staff 602 2016-06-09 16:03
> /user/hive/warehouse/t/base_0000016/bucket_00000
> drwxr-xr-x - ekoifman staff 0 2016-06-09 16:07
> /user/hive/warehouse/t/base_0000017
> -rw-r--r-- 1 ekoifman staff 588 2016-06-09 16:07
> /user/hive/warehouse/t/base_0000017/bucket_00000
> drwxr-xr-x - ekoifman staff 0 2016-06-09 16:07
> /user/hive/warehouse/t/delta_0000017_0000017_0000
> -rw-r--r-- 1 ekoifman staff 514 2016-06-09 16:06
> /user/hive/warehouse/t/delta_0000017_0000017_0000/bucket_00000
> drwxr-xr-x - ekoifman staff 0 2016-06-09 16:07
> /user/hive/warehouse/t/delta_0000018_0000018_0000
> -rw-r--r-- 1 ekoifman staff 612 2016-06-09 16:07
> /user/hive/warehouse/t/delta_0000018_0000018_0000/bucket_00000
> {noformat}
> then do _alter table T compact 'minor';_
> then we end up with
> {noformat}
> drwxr-xr-x - ekoifman staff 0 2016-06-09 16:07
> /user/hive/warehouse/t/base_0000017
> -rw-r--r-- 1 ekoifman staff 588 2016-06-09 16:07
> /user/hive/warehouse/t/base_0000017/bucket_00000
> drwxr-xr-x - ekoifman staff 0 2016-06-09 16:11
> /user/hive/warehouse/t/delta_0000018_0000018
> -rw-r--r-- 1 ekoifman staff 500 2016-06-09 16:11
> /user/hive/warehouse/t/delta_0000018_0000018/bucket_00000
> drwxr-xr-x - ekoifman staff 0 2016-06-09 16:07
> /user/hive/warehouse/t/delta_0000018_0000018_0000
> -rw-r--r-- 1 ekoifman staff 612 2016-06-09 16:07
> /user/hive/warehouse/t/delta_0000018_0000018_0000/bucket_00000
> {noformat}
> So compaction created a new dir _/user/hive/warehouse/t/delta_0000018_0000018_
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