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https://issues.apache.org/jira/browse/HBASE-4344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13113387#comment-13113387
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Amitanand Aiyer commented on HBASE-4344:
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@stack: Yes. I agree, this is not really cleaned up. Wanted to put it out as v1
to get feedback on the approach.
One of the reasons why I went with adding the memstoreTS to HFile was indeed to
minimize changes. Although, after
getting my feet wet, I did also consider moving along the direction of
modifying the byte buffer itself to include
the memstoreTS.
I felt like this would be simpler. The way I like to see it, memstoreTS is some
"system level timestamp" that is
somewhat transparant to the client/users. Wanted to keep it that way, as the
key-values that are in memstore keep
the timestamp separate.
I agree about the fact that we are exposing the key-value internals to the
HFile writer/readers. Perhaps, we should
get rid of it. Will be happy to do that, as a separate diff, once we get the
core issue fixed.
also working on a diff to see if we can use the hlog sequence id as the
memstoreTS ... will put it out separately.
> Persist memstoreTS to disk
> --------------------------
>
> Key: HBASE-4344
> URL: https://issues.apache.org/jira/browse/HBASE-4344
> Project: HBase
> Issue Type: Sub-task
> Reporter: Amitanand Aiyer
> Assignee: Amitanand Aiyer
> Fix For: 0.89.20100924
>
> Attachments: 4344-v2.txt, 4344-v4.txt, 4344-v5.txt, 4344-v6.txt,
> 4344-v7.txt, 4344-v8.txt, patch-2
>
>
> Atomicity can be achieved in two ways -- (i) by using a multiversion
> concurrency system (MVCC), or (ii) by ensuring that "new" writes do not
> complete, until the "old" reads complete.
> Currently, Memstore uses something along the lines of MVCC (called RWCC for
> read-write-consistency-control). But, this mechanism is not incorporated for
> the key-values written to the disk, as they do not include the memstore TS.
> Let us make the two approaches be similar, by persisting the memstoreTS along
> with the key-value when it is written to the disk.
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