Re: [Postgres-xc-developers] Savepoints

[Amit K. <ami...@en...>]

Just to keep everyone aware... to support savepoints, it is required to
implement the underlying functionality, namely subtransactions.
Subtransactions are used in multiples scenarios. Besides savepoints, the
procedural languages like pl/pgsql and pl/perl also use subtransactions.
Due to the lack of subtransaction support, the exception blocks in pl/pgsql
do not work currently.

So rather than propagating SAVEPOINT command to the cluster nodes, we need
to propagate some commands at some point when  CommitSubTransaction() and
BeginInternalSubTransaction() are called. There is currently no explicit
SQL command to commit a subtransaction, or start a subtransaction.
SAVEPOINT command can be used to begin a remote subtransaction block. But
there does not seem to be a way to commit that sub-transaction block
remotely.

This is just some food for thought in case somebody is thinking of
implementing the functionality. There might be many more issues, but not
sure right now. There is nothing to handle 2PC for subtransactions because
there does not seem to be a corresponding PREPARE TRANSACTION for
subtransactions. But possibly there could be some way out.



On 3 September 2013 23:12, Leonard Boyce <le...@si...> wrote:

> Hi Pavan,
>
> Unfortunately we do not have the expertise to tackle this in-house. A
> "bounty" on the feature may make sense, but without understanding the scale
> or complexity of the feature itself it is extremely difficult to even
> propose such to my higher ups.
> With other projects it would be easier to gauge the 'value' as there is
> (in may cases) a history of previous bounties.
>
> Any help or direction here would be appreciated.
> Thanks,
> Leonard
>
>
> On Sun, Sep 1, 2013 at 11:32 PM, Pavan Deolasee <pav...@gm...>wrote:
>
>> On Sat, Aug 31, 2013 at 1:33 AM, Leonard Boyce <le...@si...>wrote:
>>
>>> Hi all,
>>>
>>> We've been eagerly following XC since it's first announcement and are
>>> eager to start testing XC. We had to wait for trigger support, but it
>>> seems our only remaining barrier is no support for savepoints.
>>>
>>>
>> Apart from waiting on the team to implement the missing feature, do you
>> think you or someone else in your organisation has skills/time to give it a
>> shot ? IMHO the core team will have limited time and resources to keep
>> adding new features. Another possibility is to fund the development so that
>> someone who has time and skills can speedtrack the development. That's a
>> model often used by other open source projects including PostgreSQL.
>>
>> Thanks,
>> Pavan
>> --
>> Pavan Deolasee
>> http://www.linkedin.com/in/pavandeolasee
>>
>
>
>
> --
> Kind regards,
> Leonard Boyce
> http://www.siftlogic.com
> (m) 305-3351268
> (s) leonard.boyce
>
>
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