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https://issues.apache.org/jira/browse/HBASE-1880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12761466#action_12761466
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stack commented on HBASE-1880:
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Patch looks good. Moving writeToWAL till after the timestamp gets set seems
like a no duh kinda thing (Can you fix the formatting -- its anti-easy-read at
moment obviously product of a machine formatter).
So, no more reconstructeCache, just insert straight into memstore? That solves
another problem I was worried about in that we keep an eye on size of memstore
but not on this reconstructionCache. Removing it looks like a good move.
So, these new edits are not going into a WAL at all? They should? (Make a new
issue? My sense is when a working flush all of our recovery will need to come
out of the dark and get a spotlight shone on it).
> 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.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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