[postgis-tickets] [PostGIS] #2755: 4 regression failures for sfcgal

[PostGIS]

#2755: 4 regression failures for sfcgal
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  Reporter:  robe     |       Owner:  colivier     
      Type:  defect   |      Status:  reopened     
  Priority:  blocker  |   Milestone:  PostGIS 2.2.0
 Component:  sfcgal   |     Version:  trunk        
Resolution:           |    Keywords:               
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Comment(by vmo):

 Replying to [comment:6 pramsey]:
 > You can't just toss r12350, it's necessary to support extension upgrade,
 because during upgrade two libpostgis.so libraries are simultaneously
 loaded and they will collide on the GUC variable and upgrade will halt
 unless you check and avoid double-defining it.

 I'm working on it, but as far as I can tell, the proposed solution does
 not seem to work.

 When changing postgis.backend, maybe because the custom variable is
 already defined as a place holder, r13250 causes the assign hook
 definition to be bypassed. As a result geos function are called instead of
 sfcgal ones (some tests failures, like ST_Distance(geom, empty) show
 that).

 I asked on pg-hackers (http://postgresql.1045698.n5.nabble.com/modify-
 custom-variables-td5808161.html) and I was advised to avoid loading the
 old postgis.so before upgrade.

 I tend to agree: if you skip the definition of the custom variable, the
 assign hook will still point to the old version of the library, and we
 will end-up calling sfcgal backend from the previous version of
 postgis*.so

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/2755#comment:7>
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