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From "deepankar (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-16624) MVCC DeSerialization bug in the upstream HFileScannerImpl
Date Tue, 13 Sep 2016 05:59:20 GMT
deepankar created HBASE-16624:
---------------------------------

             Summary: MVCC DeSerialization bug in the upstream HFileScannerImpl
                 Key: HBASE-16624
                 URL: https://issues.apache.org/jira/browse/HBASE-16624
             Project: HBase
          Issue Type: Bug
          Components: HFile
    Affects Versions: 2.0.0
            Reporter: deepankar
            Assignee: deepankar
            Priority: Blocker


My colleague [~naggarwal] found a bug in the deserialization of mvcc from HFile, As a part
of the optimization of deserialization of VLong, we read a int at once but we forgot to convert
it to unsigned one. 

This would cause issues because once we cross the integer threshold in sequenceId and a compaction
happens we would write MAX_MEMSTORE_TS in the trailer as 0 (because we will be reading negative
values from the file that got flushed with sequenceId > Integer.MAX_VALUE). And once we
have MAX_MEMSTORE_TS as 0, and there are sequenceId values present alongside with KeyValues
the regionserver will now start failing to read the compacted file and thus corruption. 

Interestingly this would happen only on the tables that don't have  DataBlockEncoding enabled
and unfortunately in our case that turned out to be META and a another small table.

Fix is small (~20 chars) and attached



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