<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META content="MSHTML 6.00.2900.2180" name=GENERATOR></HEAD>
<BODY>
<DIV><FONT face=Arial size=2><SPAN
class=969370715-29092004>Hello,</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004> I'm trying to
do some processing on a roads layer and simplify it for rendering speed.
In ArcInfo, I would use a dissolve on the hwy_num field and then simplify it to
500 meters.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=969370715-29092004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004> From the
documentation, PostGIS seems like it can do the same thing, first selecting into
a new table using either the GeomUnion or Collect aggregates and then again
using simplify, however using simplify returns the following
error:</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2></FONT></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2>ERROR: out of memory<BR>DETAIL: Failed on request of size
4172712.</FONT></SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2></FONT></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT size=2>here is
my query:</FONT></SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2> select hwy_num, simplify(the_geom, 500) as the_geom
from ra1bb</FONT></SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2></FONT></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT size=2>where
ra1bb is created from:</FONT></SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2> select hwy_num, geomunion(the_geom) as the_geom into
ra1bb from ra1 group by hwy_num</FONT></SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2></FONT></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT size=2>Another
question: what is the difference between collect and geomunion (besides
speed)? Which one would better approximate an ArcInfo dissolve
function?</FONT></SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2></FONT></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2>Thanks,</FONT></SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT
size=2></FONT></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=969370715-29092004><FONT size=2>John
Cole</DIV></FONT></SPAN></FONT><br>-------------------------------------<br>This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail.</BODY></HTML>