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From "Duo Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17407) Correct update of maxFlushedSeqId in HRegion
Date Wed, 04 Jan 2017 09:22:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15797741#comment-15797741

Duo Zhang commented on HBASE-17407:

We are not end users, we are developers, so we can see the internal stage of a transaction.
Think of a typical transaction that, transfer 1000 USD from A to B.  No doubt you will minus
1000 from A, then plus 1000 to B, right? You will not minus 10000 from A, plus 1000 to B and
then plus 9000 to A right?

What I mean is that, you can have intermediate state, but this does not mean it is a good
idea to have a strange intermediate state. The value in  It is easy to make developers confusing
and introduce bugs in the future. The assumption of the currect flush is that we will flush
all data in memstore for a store, if the assumption is gone then the flow should also be changed.
Putting an obviously incorrect value in lowestUnflushedSequenceIds is not acceptable.

And what do you think of the proposal I mentioned above? I do not think it changes the way
you update WAL. Buy your finalizeFlush method does change the way we update WAL as you even
add a new method to WAL...


> Correct update of maxFlushedSeqId in HRegion
> --------------------------------------------
>                 Key: HBASE-17407
>                 URL: https://issues.apache.org/jira/browse/HBASE-17407
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Eshcar Hillel
> The attribute maxFlushedSeqId in HRegion is used to track the max sequence id in the
store files and is reported to HMaster. When flushing only part of the memstore content this
value might be incorrect and may cause data loss.

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