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https://issues.apache.org/jira/browse/HBASE-10241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13857563#comment-13857563
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stack commented on HBASE-10241:
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[~sershe] Nice writeup.
sequenceid is not scoped to the region. Ergo mvcc should be too?
bq. Client will have a configurable setting to enable consistent scanners.
IMO, just say no to more configs. When would someone want 'inconsistent
scanners'? (In my experience, users do not play with configs in 98.1745% of
cases -- smile).
bq. ....unless mvcc and seqId are merged)
Would this issue be better if above work is done first?
bq. ...Recovery will have to make use of mvcc when replaying the edit to new
server.
This work is ongoing over in @jeffrey zhong replay wal effort?
mvcc is about giving you a consistent view on a row only. This work is to deal
with the case where you have a wide row and you have already passed the client
the first half of a row, a crash happens, and you need to return to the client
the second half of the row?
A section in doc. on implications of not having this change fixed and then the
'cost' of this fix going in would help.
Thanks for working on this tough one [~sershe]
[~lhofhansl] One for you to peruse boss...
> implement mvcc-consistent scanners (across recovery)
> ----------------------------------------------------
>
> Key: HBASE-10241
> URL: https://issues.apache.org/jira/browse/HBASE-10241
> Project: HBase
> Issue Type: New Feature
> Components: HFile, regionserver, Scanners
> Affects Versions: 0.99.0
> Reporter: Sergey Shelukhin
> Assignee: Sergey Shelukhin
> Attachments: Consistent scanners.pdf
>
>
> Scanners currently use mvcc for consistency. However, mvcc is lost on server
> restart, or even a region move. This JIRA is to enable the scanners to
> transfer mvcc (or seqId, or some other number, see HBASE-8763) between
> servers. First, client scanner needs to get and store the readpoint. Second,
> mvcc needs to be preserved in WAL. Third, the mvcc needs to be stored in
> store files per KV and discarded when not needed.
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