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Date: Tue, 17 Jan 2012 13:52:47 -0800
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Subject: Re: Limited cross row transactions
From: Ted Yu <yuzhihong@gmail.com>
To: dev@hbase.apache.org
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Back to original proposal:
If client side grouping reveals that the batch of operations cannot be
supported by 'limited cross row transactions', what should the user do ?

Cheers

On Tue, Jan 17, 2012 at 1:49 PM, Ted Yu <yuzhihong@gmail.com> wrote:

> Whether Omid fits the bill is open to discussion.
>
> We should revisit HBASE-2315 and provide the support Flavio, et al need.
>
> Cheers
>
>
> On Tue, Jan 17, 2012 at 1:41 PM, Lars George <lars.george@gmail.com>wrote:
>
>> 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 <lhofhansl@yahoo.com>
>> 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
>> >>
>> >>
>>
>>
>

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