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https://issues.apache.org/jira/browse/HBASE-14949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15052064#comment-15052064
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Duo Zhang commented on HBASE-14949:
-----------------------------------
{quote}
SequenceId has a region scope. If you play an edit into a Region twice, it is
fine.
{quote}
So seems we do not need to skip duplicated WAL when replaying? We have a
timestamp in WAL entry so it is safe to replay multiple times. And I checked
the code again, for increment and append, we first get the row from region, do
increment or append, and log the entire cell out as WAL, so it is also safe to
replay it multiple times.
> Skip duplicate entries when replay WAL.
> ---------------------------------------
>
> Key: HBASE-14949
> URL: https://issues.apache.org/jira/browse/HBASE-14949
> Project: HBase
> Issue Type: Sub-task
> Reporter: Heng Chen
> Attachments: HBASE-14949.patch, HBASE-14949_v1.patch
>
>
> As HBASE-14004 design, there will be duplicate entries in different WAL. It
> happens when one hflush failed, we will close old WAL with 'acked hflushed'
> length, then open a new WAL and write the unacked hlushed entries into it.
> So there maybe some overlap between old WAL and new WAL.
> We should skip the duplicate entries when replay. I think it has no harm to
> current logic, maybe we do it first.
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