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HBase, mail # dev - Limited cross row transactions


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Re: Limited cross row transactions
Lars George 2012-01-17, 21:41
Hi Ted,

Wouldn't Omid (https://github.com/yahoo/omid) help there? Or is that too broad? Just curious.

Lars

On Jan 17, 2012, at 4:36 PM, Ted Yu wrote:

> Can we collect use case for 'limited cross row transactions' first ?
>
> I have been thinking about (unlimited) multi-row transaction support in
> HBase. It may not be a one-man task. But we should definitely implement it
> someday.
>
> Cheers
>
> On Tue, Jan 17, 2012 at 1:27 PM, lars hofhansl <[EMAIL PROTECTED]> wrote:
>
>> I just committed HBASE-5203 (together with HBASE-3584 this implements
>> atomic row operations).
>> Although a relatively small patch it lays the groundwork for heterogeneous
>> operations in a single WALEdit.
>>
>> The interesting part is that even though the code enforced the atomic
>> operation to be a for single row, this is not required.
>> It is enough if all involved KVs reside in the same region.
>>
>> I am not saying that we should add any high level concept to HBase (such
>> as the EntityGroups of Megastore).
>>
>> But, with a slight addition to the API (allowing a grouping of multiple
>> row operations) client applications have all the building blocks to do
>> limited cross row atomic operations.
>> The client application would be responsible for either correctly
>> pre-splitting the table, or a custom balancer has to be provided.
>>
>> The operation would fail if the regionserver determines that it would need
>> data from multiple region servers.
>>
>> I think this needs at least minimal support from HBase and cannot
>> (efficiently or without adding more moving parts) by a client API only.
>>
>>
>> Comments? Is this worth pursuing? If so, I'll file a jira and provide a
>> patch.
>>
>> Thanks.
>>
>>
>> -- Lars
>>
>>