[jira] Commented: (HBASE-1880) DeleteColumns are not recovered properly from the write-ahead-log

["Jonathan Gray (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-1880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12870242#action_12870242 ] 

Jonathan Gray commented on HBASE-1880:
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Does this issue still exist?

> 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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