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From "Samarth Jain (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-1498) Turn KEEP_DELETED_CELLS off by default
Date Tue, 02 Dec 2014 00:41:13 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-1498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14230765#comment-14230765
] 

Samarth Jain commented on PHOENIX-1498:
---------------------------------------

Allowing ALTER TABLE to set KEEP_DELETED_CELLS will work once https://issues.apache.org/jira/browse/PHOENIX-1409
(WIP) is finished.

> Turn KEEP_DELETED_CELLS off by default
> --------------------------------------
>
>                 Key: PHOENIX-1498
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-1498
>             Project: Phoenix
>          Issue Type: Bug
>    Affects Versions: 4.0.0, 5.0.0
>            Reporter: Jeffrey Zhong
>
> Phoenix table is created with "KEEP_DELETED_CELLS" enabled by default, this is only used
to allow for flashback queries to work correctly. While flashback query isn't used often in
field and we found that query performance degraded with the option on. This is likely a hbase
scan issue though(will create a JIRA once having more info). 
> Anyway Keeping deleted cells will add performance penalty and it's not used often. Therefore,
I'm suggesting to set it off by default. 
> We have a test where a table is loaded with > 5m rows and then some are deleted/reinserted.
The count ( * ) performance became worse & worse:
> {code}
> +------------+
> |  COUNT(1)  |
> +------------+
> | 5078242    |
> +------------+
> 1 row selected (33.273 seconds)
> +------------+
> |  COUNT(1)  |
> +------------+
> | 5078242    |
> +------------+
> 1 row selected (174.771 seconds)
> +------------+
> |  COUNT(1)  |
> +------------+
> | 5078242    |
> +------------+
> 1 row selected (458.251 seconds)
> {code}
> I think we can provide a table property in CREATE TABLE & ALTER TABLE statement for
people to enable KEEP_DELETED_CELLS if there is a need but by default it should be turned
off.



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