[postgis-devel] [PostGIS] #230: Put in costs in _ST and possibly other functions

[PostGIS]

#230: Put in costs in _ST and possibly other functions
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  Reporter:  nicklas  |       Owner:  robe                     
      Type:  defect   |      Status:  closed                   
  Priority:  medium   |   Milestone:  postgis 1.5.0            
 Component:  postgis  |     Version:  1.4                      
Resolution:  fixed    |    Keywords:  st_dwithin st_expand bbox
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Comment (by kneufeld):

 Paul, setting all the functional costs to 100 is a great start but
 shouldn't this ticket remain open?  I think the point of this is to inform
 PostgreSQL of functional cost estimates of every _ST function so it knows
 how to sort them in the planner.

 It's much more costly to use buffer than it is to compute the centroid of
 a geometry.  So if I have "WHERE ST_IsValid(ST_Buffer(geom)) AND
 ST_Distance(ST_Centroid(geom), 'POINT(0 0)') > 10" I would want the
 planner to automatically place the centroid calculation first, THEN
 compute buffer if the first half of the condition succeeds.

 For this, we'll need functional estimates on every function that
 appropriately estimate the cost.

 http://postgis.refractions.net/pipermail/postgis-devel/2009-
 July/006109.html

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/230#comment:24>
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