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https://issues.apache.org/jira/browse/PHOENIX-1498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14230858#comment-14230858
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Jeffrey Zhong commented on PHOENIX-1498:
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We tried several major compactions and it didn't help if
KEEP_DELETED_CELLS=true because those deleted row keys are mostly unique. When
KEEP_DELETED_CELLS=false, major compaction removes all deleted cells. In HBase
0.98, "versions=1" is set by default already.
Normal backup & restore, a user often use snapshot/export/replication.
> 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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