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From "Xing Shi (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-6195) Increment data will lost when the memstore flushed
Date Mon, 11 Jun 2012 03:00:44 GMT
Xing Shi created HBASE-6195:

             Summary: 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

There are two problems in increment() now:
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.

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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