Hi Ben,
Option A : from my own very little experience with postgis & mapserver,
you'll have a little loss of performance.
Option B : in the worst case, you'll get an error and mapserver will throw
an exception to the client.
Option C : poor guy... :)
Option D : you should maybe try to put a call to buffer around your geom
column; in some cases, it is able to do some magic results !
-- To see if the magic happens
select buffer(the_geom), IsValid(buffer(the_geom)) from gis_roads where
IsValid(the_geom) = false;
-- To select and do the magic without updates
select the_geom, count(gid) from (select buffer(the_geom) as the_geom, gid
from gis_roads) group by the_geom;
-- To update magically
update gis_roads
set the_geom = buffer(the_geom)
where IsValid(the_geom) == false;
I did not test those, so maybe it won't work...
Best regards,
Benoît
Benoît Andrieu
+33.(0)1.30.08.95.21
[email protected]
[email protected]
----- Original Message -----
From: "Ben Madin" <[email protected]>
To: <[email protected]>
Sent: Thursday, December 18, 2008 8:07 AM
Subject: [mapserver-users] Impact of InValid Geometry on PostGIS queries
G'day all,
I have a roads shapefile which I imported in PostGIS, planning to merge
several different countries data eventually. It is producing a layer on
the map, and labels etc.
However, the data isn't all good - in fact, about 10% is bad :
es=# select IsValid(the_geom), count(gid) from gis_roads group by
IsValid(the_geom);
isvalid | count
----------+-------
| 4128
t | 39670
(2 rows)
My question then is :
should I ?
a) leave it - it won't do any harm, but probably won't be rendered,
b) remove it - it may be incorrectly rendered, or waste processor time on
data that is unuseable,
c) fix it by hand (lazy git!)
d) fix it automatically, using super program I wasn't aware of. (called?)
actually, I don't have the time or budget for option c, and I suspect
option d does not exist!
cheers
Ben
--
Ben Madin
REMOTE INFORMATION
t : +61 8 9192 5455
f : +61 8 9192 5535
m : 0448 887 220
Broome WA 6725
[email protected]
Out here, it pays to know...
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