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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2405) [hbase] Merge region tool exposed in shell and/or in UI
Date Mon, 07 Jan 2008 20:57:33 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12556688#action_12556688
] 

stack commented on HADOOP-2405:
-------------------------------

Here is an (ugly) suggestion: In the UI where we list regions over on the regionserver, there
would be checkbox where regions meet  Clicking on the checkbox and submitting would run the
HRegion.merge code.

In the shell, it'd be some kind of alter table command: alter table x merge regionA regionB

But currently regions have to be offline for merges to run so this makes things a little awkward.
 Shell manages the offlining doing truncate at least. Maybe shell and UI should have means
of viewing/dealing with tables that have been offlined?  Or should we change the merge code
so it can go against onlined tables?

Billy: I don't think HADOOP-1700 a prerequisite adding this feature.  We could do something
like we do currently when we split where daughter regions are made with references to the
parent: One daughter references the top half of the daughter region and the other, the bottom
half.  Eventually the references are let go as compactions start to run in the children. 
 The new merged region could be made up of mapfiles that reference the two input regions --
a sort of reverse of the split operation.  Doing this, the merges should be as fast as splits
and could be done with the table online.

> [hbase] Merge region tool exposed in shell and/or in UI
> -------------------------------------------------------
>
>                 Key: HADOOP-2405
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2405
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: contrib/hbase
>            Reporter: stack
>            Priority: Minor
>
> hbase has support for merging regions.  Expose a merge trigger in the shell or in the
UI (Can only merge adjacent features so perhaps only makes sense in UI in the regionserver
UI).

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