Re: [v9.3] Extra Daemons (Re: elegant and effective way for running jobs inside a database)

On Thursday, September 20, 2012 1:44 AM Simon Riggs wrote:
On 12 September 2012 04:30, Amit Kapila <amit(dot)kapila(at)huawei(dot)com> wrote:
> On Tuesday, September 11, 2012 9:09 PM Alvaro Herrera wrote:
> Excerpts from Boszormenyi Zoltan's message of vie jun 29 09:11:23 -0400
2012:
>
>>>> We have some use cases for this patch, when can you post
>>>> a new version? I would test and review it.
>
>>> What use cases do you have in mind?
>
>> Wouldn't it be helpful for some features like parallel query in future?

> Trying to solve that is what delayed this patch, so the scope of this
> needs to be "permanent daemons" rather than dynamically spawned worker
> tasks.

Why can't worker tasks be also permanent, which can be controlled through
configuration. What I mean to say is that if user has need for parallel
operations
he can configure max_worker_tasks and those many worker tasks will get
created.
Otherwise without having such parameter, we might not be sure whether such
deamons
will be of use to database users who don't need any background ops.

The dynamism will come in to scene when we need to allocate such daemons
for particular ops(query), because
might be operation need certain number of worker tasks, but no such task
is available, at that time it need
to be decided whether to spawn a new task or change the parallelism in
operation such that it can be executed with
available number of worker tasks.

Although I understood and agree that such "permanent daemons" will be
useful for usecases other than
parallel operations. However my thinking is that having "permanent
daemons" can also be useful for parallel ops.
So even currently it is getting developed for certain usecases but the
overall idea can be enhanced to have them for
parallel ops as well.

With Regards,
Amit Kapila.