[postgis-devel] [PostGIS] #1053: Make transformation and projection cache API available.

[PostGIS]

#1053: Make transformation and projection cache API available.
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 Reporter:  bnordgren    |       Owner:  pramsey      
     Type:  enhancement  |      Status:  new          
 Priority:  medium       |   Milestone:  PostGIS 2.0.0
Component:  postgis      |     Version:  trunk        
 Keywords:               |  
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Comment(by bnordgren):

 I would very much like to consider the internal structure of the
 projection cache separately from it's location. Looking at this, it's just
 permeated with !MemoryContext references. Not just the cache itself, but
 every single data structure has a !MemoryContext (even the hash table
 entries). I have no idea what most of it is for, and the very idea of me
 messing with it is virtually guaranteed to wreck everything.

 I could see my way clear to putting these two functions in liblwgeom,
 however:

 {{{
 int lwgeom_transform(LWGEOM *geom, projPJ inpj, projPJ outpj) ;
 int transform_point(POINT4D *pt, projPJ srcpj, projPJ dstpj) ;
 }}}

 That way, you can transform to your heart's content provided you have a
 projPJ object. liblwgeom will gain a dependency on the proj4 library, tho,
 which is probably why I didn't do it in the first place.

 The projection cache is only used to avoid unnecessary SELECTs against the
 spatial_ref_sys table, which is a fairly strong argument to keep it out of
 liblwgeom until an alternate use is found.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1053#comment:10>
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