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From "Clint Morgan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1880) DeleteColumns are not recovered properly from the write-ahead-log
Date Sat, 22 May 2010 00:48:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12870250#action_12870250

Clint Morgan commented on HBASE-1880:

Looks like this was applied to trunk. 

> DeleteColumns are not recovered properly from the write-ahead-log
> -----------------------------------------------------------------
>                 Key: HBASE-1880
>                 URL: https://issues.apache.org/jira/browse/HBASE-1880
>             Project: Hadoop HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 0.20.0, 0.20.1, 0.21.0
>            Reporter: Clint Morgan
>            Priority: Critical
>         Attachments: 1880-v2.patch, 1880-v3.patch, 1880-v4.patch, 1880.patch
> I found a couple of issues:
>  - The timestamp is being set to now after it has been written to the wal. So if the
WAL was flushed on that write, it gets in with ts of MAX_INT and is effectively lost.
>  - Even after that fix, I had issues getting the delete to apply properly. In my case,
the WAL had a put to a column, then a DeleteColumn for the same column. The DeleteColumn KV
had a later timestamp, but it was still lost on recovery. I traced around a bit, and it looks
like the current approach of just using an HFile.writer to write the set of KVs read from
the log will not work. There is special logic in MemStore for deletes that needs to happen
before writing. I got around this by just adding to memstore in the log recovery process.
Not sure if there are other implications of this.

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