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https://issues.apache.org/jira/browse/HBASE-20182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16401956#comment-16401956
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Duo Zhang commented on HBASE-20182:
-----------------------------------
Let me try to describe it more clearly...
First the table has two regions
[-infinite, 1), [1, + infinite)
And then I split the second one, it becomes
[-infinite, 1), [1, 2), [2, +infinite)
And then I merge the first two regions, it becomes
[-infinite, 2), [2, +infinite)
So when I want to locate row 1 in the table, it should return the first region
above right? But the meta table is like this
table,,...
table,1,..., offline=true, split=true
table,2,...
See? The record for the old [1, +infinite) region is still there, with offline
= true and split = true. So if I want to locate row 1 then it will always
locate to the offlined region and throw an exception...
Is this clear enough?
Thanks.
> Can not locate region after split and merge
> -------------------------------------------
>
> Key: HBASE-20182
> URL: https://issues.apache.org/jira/browse/HBASE-20182
> Project: HBase
> Issue Type: Bug
> Components: Region Assignment
> Reporter: Duo Zhang
> Priority: Blocker
> Fix For: 2.0.0
>
> Attachments: HBASE-20182-UT.patch
>
>
> When implementing serial replication feature in HBASE-20046, I found that
> when splitting a region, we will not remove the parent region, instead we
> will mark it offline.
> And when locating a region, we will only scan one row so if we locate to the
> offlined region then we are dead.
> This will not happen for splitting, since one of the new daughter regions
> have the same start row with the parent region, and the timestamp is greater
> so when doing reverse scan we will always hit the daughter first.
> But if we also consider merge then bad things happen. Consider we have two
> regions A and B, we split B to C and D, and then merge A and C to E, then
> ideally the regions should be E and D, but actually the regions in meta will
> be E, B and D, and they all have different start rows. If you use a row
> within the range of old region C, then we will always locate to B and throw
> exception.
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