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From "Jingcheng Du (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-13922) Do not reset mvcc in compactions for mob-enabled column
Date Wed, 17 Jun 2015 07:35:01 GMT
Jingcheng Du created HBASE-13922:
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             Summary: Do not reset mvcc in compactions for mob-enabled column
                 Key: HBASE-13922
                 URL: https://issues.apache.org/jira/browse/HBASE-13922
             Project: HBase
          Issue Type: Sub-task
          Components: mob
    Affects Versions: hbase-11339
            Reporter: Jingcheng Du
            Assignee: Jingcheng Du
             Fix For: hbase-11339


In major compaction, the mvcc of cells ( whose mvcc<=readPt) are set to 0.
In some cases, this brings issues, for example the following scenario:
# We have mob enabled cf, the threshold is 5 bytes.
# Add a cell (r0,ts0,seqId=5,"mobValue0"), and flush it to a mob file.
# Add another cell (r0,ts0,seqId=10,"new"), and flush the memstore, this is not a mob cell
since it's value is smaller than 5 bytes.
# Add the third cell (r1:ts1:seqId =15, "mobValue1"), and flush it to a mob file. Now we have
two mob files.
# Now run a major compaction in hfiles, we got two cells left (r0:ts0:seqId=0,"new") and (r1:ts1:seqId=0,'mobValue1").
# Now run a mob major compaction, two mob files are merged into one. The update ref cell is
bulk loaded back to hbase, they are (r0,ts0,seqId=5,"mobValue0") and (r1:ts1:seqId=0,"mobValue1").
# Now open a scanner, the value of r0 is mobValue0 whereas the correct value new.
This issue is caused by the mvcc reset in compactions. We should disable it in compactions
for mob-enabled columns.




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