On Thu, Dec 8, 2011 at 3:11 PM, Marc Cousin <cousinmarc@gmail.com> wrote:
> Le Thu, 8 Dec 2011 12:27:22 +0000,
> Simon Riggs <simon@2ndQuadrant.com> a écrit :
>
>> On Thu, Dec 8, 2011 at 11:24 AM, Craig Ringer <ringerc@ringerc.id.au>
>> wrote:
>>
>> > Areas in which Pg seems significantly less capable include:
>>
>> Please can you explain the features Oracle has in these area, I'm not
>> clear. Thanks.
>
> Maybe I can answer from my own Oracle experience. I hope it will be what
> Craig had in mind :)
>
>>
>>
>> > - admission control, queuing and resource limiting to optimally
>> > load a machine. Some limited level is possible with external
>> > pooling, but only by limiting concurrent workers.
>
> Oracle has natively two ways of handling inbound connections:
> - Dedicated, which is very similar to the PostgreSQL way of accepting
> connections: accept(), fork() and so on
> - Shared, which is based on processes listening and handling the
> connections (called dispatchers) and processes doing the real work
> (called workers, obviously). All of this works internally with
> some sort of queuing and storing results in shared memory (I don't
> remember the details of it)
> The advantage of this second architecture being of course that you
> can't have more than N workers hitting your database simultaneously. So
> it's easier to keep the load on the server to a reasonable value.
>
>>
>> > - prioritisation of queries or users. It's hard to say "prefer this
>> > query over this one, give it more resources" or "user A's work
>> > always preempts user B's" in Pg.
>>
> It's called the resource manager in Oracle. You define 'resource plans',
> 'consumer groups', etc… and you get some sort of QoS for your queries.
> It's mostly about CPU resource allocation if I remember correctly (I
> never used it, except during training :) )
>
> Being able of changing the backend's nice level may do something
> similar I guess. I don't think Oracle's resource manager solves
> the priority inversion due to locking in the database, but I'm not sure
> of it.
Thanks, sounds interesting.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services