<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Sounds good to me. I think most people are annoyed with their whole processing failing when it hits something invalid, rather than getting some not quite right for invalid things.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> postgis-devel [mailto:postgis-devel-bounces@lists.osgeo.org] <b>On Behalf Of </b>Darafei "Kom?pa" Praliaskouski<br><b>Sent:</b> Sunday, February 04, 2018 10:01 AM<br><b>To:</b> PostGIS Development Discussion <postgis-devel@lists.osgeo.org><br><b>Subject:</b> [postgis-devel] Autofix and retry for GEOS overlay ops<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p><div><div><p class=MsoNormal style='margin-left:.5in'>Hi,<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>I've been debugging an issue with ST_Subdivide on one of our polygons. It traced down to issue in GEOS, and as a part of fix I had to replace ClipByRect with normal Intersection call. When fixing the tests for old ClipByRect, that specifically tested some invalid geometries it can process, I came up with this logic: <o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><p class=MsoNormal style='margin-left:.5in'><a href="https://github.com/postgis/postgis/pull/202/files#diff-c3dac68eb856b0a0554707e2ffcfbf17R648">https://github.com/postgis/postgis/pull/202/files#diff-c3dac68eb856b0a0554707e2ffcfbf17R648</a><o:p></o:p></p><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>which boils down to "try intersecting, if failed, MakeValid the inputs, try intersecting, fail if failed".<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>This does not make process any slower for anybody now, as current case "we got it done from first attempt" is not prepended by any additional validity check.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>Thinking of hours spent catching some invalid geometry generated by a chain of different GEOS operations, I think such change would be beneficial for all overlay operations. In case someone gets not a desired result, they can go back to checking their inputs with ST_IsValid, and performing a deep manual fix, but simple issues like bowties will start simply working.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>Thoughts?<o:p></o:p></p></div></div></div></body></html>