[postgis-tickets] [PostGIS] #2382: Can't upgrade postgis ERROR: attempt to redefine parameter "postgis.backend"

[PostGIS]

#2382: Can't upgrade postgis ERROR: attempt to redefine parameter
"postgis.backend"
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 Reporter:  robe                   |       Owner:  robe         
     Type:  defect                 |      Status:  new          
 Priority:  medium                 |   Milestone:  PostGIS 2.2.0
Component:  build/upgrade/install  |     Version:  trunk        
 Keywords:                         |  
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Comment(by pramsey):

 This is pretty awful. You can probably exercise this bug in the raster
 space by replacing one of the raster functions (would be nice to confirm
 that). I think I can see how it's happening: you've got two postgis shared
 libraries, and initially just the old one is loaded, but then you run your
 create-or-replace command referencing the other shared library, so pgsql
 loads it and calls init on it. Boom, the init tries to define the GUC,
 using a name that is already bound (by the old library) and there's your
 error.

 I'd guess the way around this is in the GUC code to check for existence of
 the parameter before attempting to bind it, and just no-op in that case,
 assuming that it only occurs in these upgrade moments and that usually a
 module won't be loaded simultaneously in the same database.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2382#comment:15>
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