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From "Zhihong Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-6195) Increment data will be lost when the memstore is flushed
Date Wed, 13 Jun 2012 02:49:44 GMT

     [ https://issues.apache.org/jira/browse/HBASE-6195?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zhihong Ted Yu updated HBASE-6195:
----------------------------------

    Attachment: 6195.addendum
    
> Increment data will be lost when the memstore is flushed
> --------------------------------------------------------
>
>                 Key: HBASE-6195
>                 URL: https://issues.apache.org/jira/browse/HBASE-6195
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>            Reporter: Xing Shi
>            Assignee: ShiXing
>         Attachments: 6195-trunk-V7.patch, 6195.addendum, HBASE-6195-trunk-V2.patch, HBASE-6195-trunk-V3.patch,
HBASE-6195-trunk-V4.patch, HBASE-6195-trunk-V5.patch, HBASE-6195-trunk-V6.patch, HBASE-6195-trunk.patch
>
>
> There are two problems in increment() now:
> First:
> I see that the timestamp(the variable now) in HRegion's Increment() is generated before
got the rowLock, so when there are multi-thread increment the same row, although it generate
earlier, it may got the lock later. Because increment just store one version, so till now,
the result will still be right.
> When the region is flushing, these increment will read the kv from snapshot and memstore
with whose timestamp is larger, and write it back to memstore. If the snapshot's timestamp
larger than the memstore, the increment will got the old data and then do the increment, it's
wrong.
> Secondly:
> Also there is a risk in increment. Because it writes the memstore first and then HLog,
so if it writes HLog failed, the client will also read the incremented value.

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