Feng Honghua created HBASE-10227:
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Summary: When a region is opened, its mvcc isn't correctly
recovered when there are split hlogs to replay
Key: HBASE-10227
URL: https://issues.apache.org/jira/browse/HBASE-10227
Project: HBase
Issue Type: Bug
Components: regionserver
Reporter: Feng Honghua
When opening a region, all stores are examined to get the max MemstoreTS and
it's used as the initial mvcc for the region, and then split hlogs are
replayed. In fact the edits in split hlogs have kvs with greater mvcc than all
MemstoreTS in all store files, but replaying them don't increment the mvcc
according at all. From an overall perspective this mvcc recovering is
'logically' incorrect/incomplete.
Why currently it doesn't incur problem is because no active scanners exists and
no new scanners can be created before the region opening completes, so the mvcc
of all kvs in the resulted hfiles from hlog replaying can be safely set to
zero. They are just treated as kvs put 'earlier' than the ones in HFiles with
mvcc greater than zero(say 'earlier' since they have mvcc less than the ones
with non-zero mvcc, but in fact they are put 'later'), and without any
incorrect impact just because during region opening there are no active
scanners existing / created.
This bug is just in 'logic' sense for the time being, but if later on we need
to survive mvcc in the region's whole logic lifecycle(across regionservers) and
never set them to zero, this bug needs to be fixed first.
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