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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2856) TestAcidGuarantee broken on trunk
Date Sat, 21 Aug 2010 00:10:18 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12900932#action_12900932
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stack commented on HBASE-2856:
------------------------------

@Pranav: Now I seem to recall Ryan remarks where the row boundary is unknowable; of how the
only way you learn of a row boundary is AFTER you've read the first on the next row.  At this
stage you have already read into the next row so can't make the memstore/hfile switch.

> TestAcidGuarantee broken on trunk 
> ----------------------------------
>
>                 Key: HBASE-2856
>                 URL: https://issues.apache.org/jira/browse/HBASE-2856
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.89.20100621
>            Reporter: ryan rawson
>            Assignee: ryan rawson
>            Priority: Blocker
>             Fix For: 0.90.0
>
>
> TestAcidGuarantee has a test whereby it attempts to read a number of columns from a row,
and every so often the first column of N is different, when it should be the same.  This is
a bug deep inside the scanner whereby the first peek() of a row is done at time T then the
rest of the read is done at T+1 after a flush, thus the memstoreTS data is lost, and previously
'uncommitted' data becomes committed and flushed to disk.
> One possible solution is to introduce the memstoreTS (or similarly equivalent value)
to the HFile thus allowing us to preserve read consistency past flushes.  Another solution
involves fixing the scanners so that peek() is not destructive (and thus might return different
things at different times alas).

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