Re: Parallell Optimizer

On 11 June 2013 01:45, Tatsuo Ishii <ishii@postgresql.org> wrote:
>> On Sat, Jun 8, 2013 at 5:04 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
>>
>>> On 7 June 2013 20:23, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>>
>>> > As for other databases, I suspect that ones that have parallel execution
>>> > are probably doing it with a thread model not a process model.
>>>
>>> Separate processes are more common because it covers the general case
>>> where query execution is spread across multiple nodes. Threads don't
>>> work across nodes and parallel queries predate (working) threading
>>> models.
>>>
>> Indeed. Parallelism based on processes would be more convenient for
>> master-master
>> type of applications. Even if no master-master feature is implemented
>> directly in core,
>>  at least a parallelism infrastructure based on processes could be used for
>> this purpose.
>
> As long as "true" synchronous replication is not implemented in core,
> I am not sure there's a value for parallel execution spreading across
> multile nodes because of the delay of data update propagation.

Please explain what you mean by the word "true" used here.

--Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services