[postgis-users] Infinite loop in st_intersects - because of incorrect data out of st_transform?

[Magnus Hagander]

Hi!

Running the following query locks up postgis completely (in
geos::algorithm::RobustDeterminant):

SELECT st_intersects(somegeometry,
'0103000020E61000000100000005000000737979F3DDCC2CC0F92154F9E7534540000000000000F07F000000000000F07F8F806E993F7E55C0304B29FFEA8554400634E8D1DD424540B5FEE6A37FCD4540737979F3DDCC2CC0F92154F9E7534540'::geometry)

I believe this is because there are infinite values in that geometry:

# select ST_AsText('0103000020E61000000100000005000000737979F3DDCC2CC0F92154F9E7534540000000000000F07F000000000000F07F8F806E993F7E55C0304B29FFEA8554400634E8D1DD424540B5FEE6A37FCD4540737979F3DDCC2CC0F92154F9E7534540'::geometry);

  st_astext
---------------------------------------------------------------------------------------------------------------------------------------------------------------
 POLYGON((-14.4001308522972 42.6555167828373,inf inf,-85.9726317957995
82.0924680617579,42.5223944076352 43.6054577711015,-14.4001308522972
42.6555167828373))
(1 row)


ISTM that this should either be rejected as an invalid geometry, or at
least not hang....


Now, this geometry actually comes back as the result of st_transform,
which suggests to me that there is *also* a bug in st_transform, which
should never output an invalid geometry. It is the result of:

st_transform('0103000020CD0B0000010000000500000099E6673CA2FC2DC1AD7BF5ED45CC534199E6673CA2FC2DC1D7BDFAF6D28960415A06E670D7E94B41D7BDFAF6D28960415A06E670D7E94B41AD7BF5ED45CC534199E6673CA2FC2DC1AD7BF5ED45CC5341',
4326)

And that geometry is valid before it goes into st_transform, from what
I can tell:
# select st_astext('0103000020CD0B0000010000000500000099E6673CA2FC2DC1AD7BF5ED45CC534199E6673CA2FC2DC1D7BDFAF6D28960415A06E670D7E94B41D7BDFAF6D28960415A06E670D7E94B41AD7BF5ED45CC534199E6673CA2FC2DC1AD7BF5ED45CC5341'::geometry);

        st_astext

----------------------------------------------------------------------------------------------------------------------------------
------------------------------------------
 POLYGON((-982609.1179802 5189911.7181081,-982609.1179802
8670871.7181081,3658670.8820198 8670871.7181081,3658670.8820198
5189911.
7181081,-982609.1179802 5189911.7181081))
(1 row)



To me this looks like bugs "below" postgis - it's certainly below the
PostgreSQL level that I know well :-) Not sure if it can be worked
around/fixed at the postgis level or if it needs to be done in the
lower level libraries, but either way it shouldn't behave this way :-)

--
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/