[postgis-devel] [PostGIS] #502: [wktraster] Optimize ST_Intersection

[PostGIS]

#502: [wktraster] Optimize ST_Intersection
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  Reporter:  pracine    |       Owner:  jorgearevalo   
      Type:  defect     |      Status:  reopened       
  Priority:  medium     |   Milestone:  WKTRaster 0.1.6
 Component:  wktraster  |     Version:  trunk          
Resolution:             |    Keywords:                 
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Changes (by pracine):

  * summary:  [wktraster] Optimize ST_Intersection when the geometry is a
              point => [wktraster] Optimize ST_Intersection

Old description:

> It might be much quicker to provide the value associated with a pixel
> intersecting with a point geometry when using ST_Intersection() by
> accessing the pixel value with ST_Value instead of vectorizing the whole
> tile. This, obviously, do not work when the intersecting geometry is a
> polygon. In this case we have to vectorize the complete raster tile.

New description:

 It might be much quicker to provide the value associated with a pixel
 intersecting with a point geometry when using ST_Intersection() by
 accessing the pixel value with ST_Value instead of vectorizing the whole
 tile. We have first to fix st_value(rast, geom) so it behave exactly as
 st_intersect on edge of raster and pixels.

 This, obviously, do not work when the intersecting geometry is a line or a
 polygon. In this case we should try to vectorize only the intersecting
 part of the raster tile.

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/502#comment:3>
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