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HBase >> mail # dev >> HBase - Secondary Index


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Re: HBase - Secondary Index
On 12/05/2012 12:04 PM, Anoop Sam John wrote:
>           Yes we guarentee the consistency between user table and index table. The put operation will be handled as a transactional way so as to make sure the data is added to both tables or reverted back from both. Some new CP hooks we have added for this obviously.

Would you be interested in sharing how exactly you guarantee this
consistency? What are the CP hooks that you added and how exactly are
they used?

I can currently only guess how it could work in your implementation. For
examply it could be that an update is a single WALEdit, which results in
an update to both the source and index table. If the region server
crashes between the update to the source and the index table, the HLog
will be replied and thus you will have a chance to recover. However if
the update to the index table (after a succesful update of the source
table) fails for some other reason (without a crash of the region
server), the HLog will not be replayed..

Anyway, the above is just one assumption of your implementation could
work. If you could share more details of the actual implementation, this
would be helpful.

Thanks
Jan