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