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From "Duo Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18989) Polish the compaction related CP hooks
Date Thu, 12 Oct 2017 04:05:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16201410#comment-16201410
] 

Duo Zhang commented on HBASE-18989:
-----------------------------------

As discussed in HBASE-18906, we should give CP users the ability to know when a compaction
is end. We already have a CompactionLifeCycleTracker but the problem is that it will not notify
user if the compaction can not be scheduled.

And also, as we decide not to expose StoreScanner to CP users, then it does not make sense
to allow CP users to return an InternalScanner before we actually create the StoreScanner
in our own code. In the example in HBASE-18747 I wrap the InternalScanner and then do filtering
in the preCompact method. I think this is the correct way to do filtering on compaction and
flush.

The limitation of this solution is that, we can only remove data when compaction or flush.
In the old example, we can reset the TTL in ScanInfo to include more data.But I think this
is acceptable as you can use a longer TTL(such as for ever) to include the data, and also
set KEEP_DELETE_CELLS to true and increase the versions to let compaction and flush give you
the data you want, and then do filtering.

Another problem maybe performance. When using the original filter or other things such as
TTL, the StoreScanner may do a seek other than skip if you want to jump to the next row or
column, but for now you can only do skip. But I think this is OK for most cases as usually
a row will not be very large. And compaction is not on the critical path of normal operation.

Thanks.

> Polish the compaction related CP hooks
> --------------------------------------
>
>                 Key: HBASE-18989
>                 URL: https://issues.apache.org/jira/browse/HBASE-18989
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Compaction, Coprocessors
>            Reporter: Duo Zhang
>            Assignee: Duo Zhang
>             Fix For: 2.0.0-alpha-4
>
>




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