set the cost of an aggregate function

2009/11/30 Jaime Casanova <jcasanov@systemguards.com.ec>:

Hi,

why we can't do $subject? it could have any benefit on the planner?

seems like while we can set the cost of the state transition function,
that cost is not propagated...

--
Atentamente,
Jaime Casanova
Soporte y capacitación de PostgreSQL
Asesoría y desarrollo de sistemas
Guayaquil - Ecuador
Cel. +59387171157

On Mon, Nov 30, 2009 at 11:53 AM, Jaime Casanova
<jcasanov@systemguards.com.ec> wrote:

2009/11/30 Jaime Casanova <jcasanov@systemguards.com.ec>:

Hi,

why we can't do $subject? it could have any benefit on the planner?

seems like while we can set the cost of the state transition function,
that cost is not propagated...

I thought for sure you must be wrong about this, but I just read the
source code and, sure enough, the cost of the transition and final
functions are totally ignored. In fact, there's a comment about this
in cost_agg():

* Note: ideally we should use the pg_proc.procost costs of each
* aggregate's component functions, but for now that seems like an
* excessive amount of work.

...Robert

On Mon, 2009-11-30 at 11:53 -0500, Jaime Casanova wrote:

2009/11/30 Jaime Casanova <jcasanov@systemguards.com.ec>:

Hi,

why we can't do $subject? it could have any benefit on the planner?

seems like while we can set the cost of the state transition function,
that cost is not propagated...

The cost of comparison functions is not considered in cost_sort()
either.

The answer is nobody got round to enhancing this yet and well considered
proposals and subsequent patches would be welcome.

--
Simon Riggs www.2ndQuadrant.com

On Thu, Dec 3, 2009 at 7:19 AM, Simon Riggs <simon@2ndquadrant.com> wrote:

The answer is nobody got round to enhancing this yet and well considered
proposals and subsequent patches would be welcome.

what is a well considered proposal in this area? the transition
function cost should be applied to every row cost (maybe multiplied to
cpu_operator_cost or cpu_tuple_cost) and the final function cost
should be applied just once, no?

--
Atentamente,
Jaime Casanova
Soporte y capacitación de PostgreSQL
Asesoría y desarrollo de sistemas
Guayaquil - Ecuador
Cel. +59387171157