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https://issues.apache.org/jira/browse/HBASE-6195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13292862#comment-13292862
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Zhihong Ted Yu commented on HBASE-6195:
---------------------------------------
In patch v3:
{code}
+ long now = EnvironmentEdgeManager.currentTimeMillis();
Integer lid = getLock(lockid, row, true);
{code}
Variable now isn't actually referenced. Do we need it ?
{code}
+ //store the kvs to the tmp memory for write hlog first, then write
memory
{code}
The above should read: 'to temporary memstore before writing HLog'
> Increment data will lost when the memstore flushed
> --------------------------------------------------
>
> Key: HBASE-6195
> URL: https://issues.apache.org/jira/browse/HBASE-6195
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Reporter: Xing Shi
> Attachments: HBASE-6195-trunk-V2.patch, HBASE-6195-trunk-V3.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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