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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>For completeness, I ticketed this issue. Feel free to add to it.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><a href="https://trac.osgeo.org/postgis/ticket/3777">https://trac.osgeo.org/postgis/ticket/3777</a><o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='margin-left:.5in'><b>From:</b> Regina Obe [mailto:lr@pcorp.us] <br><b>Sent:</b> Wednesday, June 21, 2017 8:18 AM<br><b>To:</b> 'PostGIS Users Discussion' <postgis-users@lists.osgeo.org><br><b>Subject:</b> RE: [postgis-users] Strange behavior with empty geometries GROUP BY<o:p></o:p></p></div></div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Pierre,<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Very interesting. Does seem to be a bug somewhere.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Seems almost like in one case the POINT(0 0) is getting a box and in other cases it's not. Perhaps same thing is happening with POINT EMPTY.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>I know we had a bug a while back where all the points were getting cached boxes. This might be left over from that issue when we fixed that is my only guess.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Luckily I still have a server (about to destroy) running PostGIS 1.5.5 which should pre-date this bug and gave this query a try and it gave the below output. <o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>I think because there was a time way back for some reason POINT(0 0 ) was a stand in for POINT EMPTY and ST_AsText couldn't represent POINT EMPTY so output GEOMETRYCOLLECTION EMPTY.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Thus you see 2 instances of GEOMETRY COLLECTION (one presumably aggregating the true GEOMETRYCOLLECTION EMPTY and another aggregating the POINT(0 0) with the POINT EMPTY.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Perhaps we've got bits of our translation somewhere that sort of still thinks that at whim.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT ST_AsText(geom) txt, count(*)<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>FROM (<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT 'POINT(0 0)'::geometry geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT 'POINT(0 0)'::geometry geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT 'POINT(0 0)'::geometry geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT 'POINT(0 1)'::geometry geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT 'LINESTRING(0 0,0 1)'::geometry geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT 'GEOMETRYCOLLECTION EMPTY'::geometry geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT 'POINT EMPTY'::geometry geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>) foo<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>GROUP BY geom;<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Output: <o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'> txt | count<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>--------------------------+-------<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>GEOMETRYCOLLECTION EMPTY | 4<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>LINESTRING(0 0,0 1) | 1<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>GEOMETRYCOLLECTION EMPTY | 1<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>POINT(0 1) | 1<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>(4 rows)<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Flash back to the present PostGIS 2.3/PostGIS 2.4 which is what you are seeing.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Right now EMPTY's should have null boxes and POINTS and 2 point lines should have no boxes, so they are aggregated the same.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Thus the answer should be along lines of below query.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>----<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>I would have expected the result to be something along the lines of:<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT ST_AsText(geom) txt, count(*)<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>FROM (<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT Box2D('POINT(0 0)'::geometry)::geometry AS geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT Box2D('POINT(0 0)'::geometry)::geometry AS geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT Box2D('POINT(0 0)'::geometry)::geometry AS geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT Box2D('POINT(0 1)'::geometry)::geometry AS geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT Box2D('LINESTRING(0 0,0 1)'::geometry)::geometry AS geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT Box2D('GEOMETRYCOLLECTION EMPTY'::geometry) AS geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>UNION ALL<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>SELECT Box2D('POINT EMPTY'::geometry) AS geom<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>) foo<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>GROUP BY geom;<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>And as you pointed out, it is not.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'> txt | count<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>---------------------+-------<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>POINT(0 0) | 3<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>LINESTRING(0 0,0 1) | 1<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>POINT(0 1) | 1<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>NULL | 2<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>(4 rows)<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Don't know what to say Pierre. You've found a gremlin lurking in the woods.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>Regina<o:p></o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='margin-left:1.0in'><b>From:</b> postgis-users [<a href="mailto:postgis-users-bounces@lists.osgeo.org">mailto:postgis-users-bounces@lists.osgeo.org</a>] <b>On Behalf Of </b>Pierre Racine<br><b>Sent:</b> Tuesday, June 20, 2017 5:42 PM<br><b>To:</b> 'PostGIS Users Discussion' <<a href="mailto:postgis-users@lists.osgeo.org">postgis-users@lists.osgeo.org</a>><br><b>Subject:</b> [postgis-users] Strange behavior with empty geometries GROUP BY<o:p></o:p></p></div></div><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>Hi,<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>When I try to count the occurrence of a number of empty geometries like this:<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT ST_AsText(geom) txt, count(*)<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>FROM (<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'POINT(0 0)'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'POINT(0 0)'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'POINT(0 0)'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'POINT(0 1)'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'LINESTRING(0 0,0 1)'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'GEOMETRYCOLLECTION EMPTY'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'POINT EMPTY'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>) foo<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>GROUP BY geom;<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>The 'GEOMETRYCOLLECTION EMPTY' and the 'POINT EMPTY' do not aggregate and I get:<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>txt count<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>POINT(0 0) 2<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>POINT EMPTY 1<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>POINT(0 0) 1<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>LINESTRING(0 0,0 1) 1<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>GEOMETRYCOLLECTION EMPTY 1<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>POINT(0 1) 1<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>If I remove any geometry other than the two EMPTY ones like this (I removed the first one 'POINT(0 0)'), the two EMPTY geometries DO aggregate:<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT ST_AsText(geom) txt, count(*)<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>FROM (<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'POINT(0 0)'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'POINT(0 0)'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'POINT(0 1)'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'LINESTRING(0 0,0 1)'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'GEOMETRYCOLLECTION EMPTY'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>UNION ALL<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>SELECT 'POINT EMPTY'::geometry geom<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>) foo<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>GROUP BY geom;<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>Result:<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>txt count<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>POINT(0 0) 2<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>LINESTRING(0 0,0 1) 1<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>POINT EMPTY 2<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'>POINT(0 1) 1<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>Any idea why empty geometries aggregation seem so dependent on what others geoms are in the table?<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>Sorry I could not build a more simple example.<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>Thanks,<o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:1.0in'>Pierre<o:p></o:p></p></div></body></html>