<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=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:"Century Gothic";
panose-1:2 11 5 2 2 2 2 2 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hey Chris – Thanks for your response.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>With regard to ST_Difference, what I was trying to accomplish is a “deletion” or “clipping out” of rivers and lakes from a parcel file. Both are vector files. Based on your description, it sounds like I’m using the wrong query. Do you know which one I should be using?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>And with regard to both the ST_Intersection and ST_Difference… yes, I am using vector files with HUGE, complex polygons that spread over very large areas (hundreds of miles). I can dice these in ArcGIS or something like that before throwing the files over the fence into Postgres. But I’m still confused by the fact that similar operations run so quickly on the exact same files in ArcGIS. I feel like there is something I’m totally missing about how to set up these queries correctly in PostGIS.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>If you or anyone have any last thoughts, I’d be really interested.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks again,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>~ Sheara<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Century Gothic","sans-serif";color:gray;letter-spacing:1.0pt'>Sheara Cohen</span></b><span style='font-size:9.0pt;font-family:"Century Gothic","sans-serif"'><br></span><span style='font-size:7.5pt;font-family:"Century Gothic","sans-serif";font-variant:small-caps;color:gray;letter-spacing:1.4pt'>Planner</span><span style='letter-spacing:1.0pt'><o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span style='font-size:10.0pt;font-family:"Century Gothic","sans-serif";color:#E9935F'>C A L T H O R P E</span></b><b><span style='font-size:10.0pt;font-family:"Century Gothic","sans-serif";color:gray'> A S S O C I A T E S</span></b><span style='font-size:10.0pt;font-family:"Century Gothic","sans-serif";color:gray'><br></span><span style='font-size:7.5pt;font-family:"Century Gothic","sans-serif";color:gray'>2095 ROSE STREET, SUITE 201, BERKELEY, CALIFORNIA, 94709 USA</span><span style='font-size:8.0pt;font-family:"Century Gothic","sans-serif"'><br></span><span style='font-size:7.5pt;font-family:"Century Gothic","sans-serif";color:gray'>510 809-1165 (direct) | 510-548-6800 x35 (main) | 510 548-6848 (fax)<br><a href="mailto:sheara@calthorpe.com"><span style='color:blue'>sheara@calthorpe.com</span></a> | <a href="www.calthorpe.com"><span style='color:blue'>www.calthorpe.com</span></a><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>