[postgis-devel] [PostGIS] #253: Gist causes wrong result from ~=

[PostGIS]

#253: Gist causes wrong result from ~=
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 Reporter:  nicklas  |       Owner:  pramsey      
     Type:  defect   |      Status:  new          
 Priority:  medium   |   Milestone:  postgis 1.5.0
Component:  postgis  |     Version:  1.4.X        
 Keywords:           |  
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 Something seems to have happen between postgis 1.3 and 1.4 or postgresql
 8.3 to 8.4.
 I couldn't reproduce on 8.3 1.3, but on 8.4 both with trunk and realeased
 1.4.0

 When running this on the attached dataset:


 select a.the_geom ~= b.the_geom  from test a,test b where a.gid != b.gid
 and a.the_geom ~= b.the_geom;

 I get the little bit absurd answer:[[BR]]
 1537;1553;f[[BR]]
 1553;1537;f[[BR]]


 so the answer from ~= is different when appearing in the select-part then
 in the where-part

 Without the index this doesn't happen. Then they are sorted away by the
 where-part.
 Also if I take away any of the other polygons of the set this fenomena
 dissapears. My conclusion is this indicates that the gist-index is
 involved when built on this particular dataset. The dataset was bigger
 from the beginning but I tried to take away as much as possible still
 preserving the error.

 Something seems to have happen between postgis 1.3 and 1.4 or postgresql
 8.3 to 8.4.
 I couldn't reproduce on 8.3 1.3, but on 8.4 both with trunk and realeased
 1.4.0

 /Nicklas

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/253>
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