[postgis-tickets] [PostGIS] #2898: Define a guideline for function cost

[PostGIS]

#2898: Define a guideline for function cost
-------------------------+--------------------------------------------------
 Reporter:  strk         |       Owner:  pramsey      
     Type:  enhancement  |      Status:  new          
 Priority:  medium       |   Milestone:  PostGIS 2.2.0
Component:  postgis      |     Version:  trunk        
 Keywords:               |  
-------------------------+--------------------------------------------------

Comment(by strk):

 Example guideline for rasters:
 {{{
 -- COST assignment guideline (TODO):
 --
 -- By default C functions get assigned a cost of 1 while (plpg)sql
 functions
 -- get assigned a cost of 100. Value expressed in "cpu_operator_cost"
 units.
 -- See http://www.postgresql.org/docs/9.1/static/runtime-config-query.html
 #GUC-CPU-OPERATOR-COST
 --
 -- The following schema can be used as a guideline to set cost of each
 -- function. The multiplier would apply to the language based default
 -- (1 or 100) and to the number of raster arguments.
 --
 -- For example a multiplier of 500 for a C function taking 2 rasters
 -- and performing operations on each of their pixel would have a cost
 -- of 1000.
 --
 --  o Only detoast raster header
 --    x 1
 --
 --  o Detoast whole raster
 --    x 100
 --
 --  o Scan each raster pixel
 --    x 300
 --
 --  o Perform operations on each raster pixel
 --    x 500
 }}}

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2898#comment:1>
PostGIS <http://trac.osgeo.org/postgis/>
The PostGIS Trac is used for bug, enhancement & task tracking, a user and developer wiki, and a view into the subversion code repository of PostGIS project.