Yes, that is the way it works.
On 2/15/2012 3:16 PM, Bistrais, Bob wrote:
OK, that seems to work by adding the map_bk_lot field. If I needed to add more
fields to the subquery, would I simply add them in with commas separating them?
Example:
(select gid, map_bk_lot, another_field1, another_field2, ST_Simplify(the_geom,
10.0)
-----Original Message-----
From: postgis-users-boun...@postgis.refractions.net
[mailto:postgis-users-boun...@postgis.refractions.net] On Behalf Of Stephen
Woodbridge
Sent: Wednesday, February 15, 2012 3:06 PM
To: postgis-users@postgis.refractions.net
Subject: Re: [postgis-users] advice for quicker display?
Actually it does NOT exist in the sub-query. Mapserver modifies the
query because it needs the label text. So you sub-query needs to have
ALL potential columns that you might need explicitly referenced.
DATA "the_geom from (select gid, map_bk_lot, ST_Simplify(the_geom, 10.0)
as the_geom from mytable) as foo USING SRID=26919 USING Unique gid"
-Steve W
On 2/15/2012 2:58 PM, Bistrais, Bob wrote:
Interesting- that works until I zoom in to about 1:50000 scale, then
the layer stops drawing with this error:
prepare_database(): Query error. Error declaring cursor: ERROR:
column "map_bk_lot" does not exist LINE 1: DECLARE mycursor BINARY
CURSOR FOR SELECT "map_bk_lot"::text... ^
With query string: DECLARE mycursor BINARY CURSOR FOR SELECT
"map_bk_lot"::text,asbinary(force_collection(force_2d(the_geom)),'NDR'),gid::text
from (select gid, ST_Simplify(the_geom, 10.0) as the_geom from
parcels) as foo WHERE the_geom&& setSRID('BOX3D(438251.727851473
4907493.5454546,445395.272148527 4910840.4545454)'::BOX3D, 26919 )
---Once again, the map_bk_lot column does indeed exist. It will
redraw fine when I zoom out again.
-----Original Message----- From:
postgis-users-boun...@postgis.refractions.net
[mailto:postgis-users-boun...@postgis.refractions.net] On Behalf Of
Sandro Santilli Sent: Wednesday, February 15, 2012 2:50 PM To:
PostGIS Users Discussion Subject: Re: [postgis-users] advice for
quicker display?
On Wed, Feb 15, 2012 at 02:26:19PM -0500, Bistrais, Bob wrote:
I tried this, but replacing mytable with parcels, it didn't draw,
the MapServer error log says "Query error. Error declaring cursor:
ERROR: column "gid" does not exist LINE 1:
...inary(force_collection(force_2d(the_geom)),'NDR'),gid::text
..."
-although the column gid does exist.
You need to select it in the subquery:
DATA "the_geom from (select gid, ST_Simplify(the_geom, 10.0) as
the_geom from mytable) as foo USING SRID=26919 USING Unique gid"
--strk;
-----Original Message----- From:
postgis-users-boun...@postgis.refractions.net
[mailto:postgis-users-boun...@postgis.refractions.net] On Behalf Of
Stephen Woodbridge Sent: Wednesday, February 15, 2012 12:26 PM To:
postgis-users@postgis.refractions.net Subject: Re: [postgis-users]
advice for quicker display?
DATA "the_geom from (select ST_Simplify(the_geom, 10.0) as the_geom
from mytable) as foo USING SRID=26919 USING Unique gid"
On 2/15/2012 11:03 AM, Bistrais, Bob wrote:
OK, I am trying to use the ST_simplify command but I'm not doing
it right. I am using a layer called parcels, it has columns gid
and the_geom, this is the DATA line from my MapServer map file:
DATA "the_geom from (ST_Simplify(the_geom, 10.0)) USING
SRID=26919 USING Unique gid"
What am I doing wrong here?
*From: * postgis-users-boun...@postgis.refractions.net
[mailto:postgis-users-boun...@postgis.refractions.net] *On Behalf
Of *Juan Marín Otero *Sent:* Tuesday, February 14, 2012 3:13 PM
*To:* PostGIS Users Discussion *Subject:* Re: [postgis-users]
advice for quicker display?
You can find the documentation here. Also look at
ST_SimplifyPreserveTopology, might be better depending on how
strict you are with how your data gets modified.
http://postgis.org/docs/ST_Simplify.html
On Tue, Feb 14, 2012 at 3:09 PM, Bistrais,
Bob<bob.bistr...@maine.gov<mailto:bob.bistr...@maine.gov>>
wrote:
Wow! Where are the ST_Simplify and other functions docuemented-
in PostGIS docs or MapServer docs?
*From: * postgis-users-boun...@postgis.refractions.net
<mailto:postgis-users-boun...@postgis.refractions.net>
[mailto:postgis-users-boun...@postgis.refractions.net
<mailto:postgis-users-boun...@postgis.refractions.net>] *On
Behalf Of *pcr...@pcreso.com<mailto:pcr...@pcreso.com> *Sent:*
Tuesday, February 14, 2012 2:44 PM *To:* PostGIS Users
Discussion *Subject:* Re: [postgis-users] advice for quicker
display?
Also,
In Postgis you can use the ST_Simplfy() function in mapserver
zoom (scale dependent) layers. So you have one dataset, and as
you zoom out you display features represented by progressively
fewer vertices. You don't need every headland of a global
coastline dataset plotted until you until you zoom in. This can
give vastly better performance than a shapefile when zoomed out.
You can use pre-prepared geometries, so each record has more than
one geometry column, or you can do the point reduction on the fly
(in the SQL command in the mapfile DATA statement), whichever
meets your needs.
The default Postgres configuration is for pretty basic hardware.
You might find& run pgtune, or look at the postgres admin docs
to configure it to more effectively use the available memory, and
see how to use tablespaces to manage data& indexes across
filesystems to increase overall disk throughput.
So it takes some work, but overall, Postgis provides spatial
data management tools with substantial performance optimisation
capabilities. But you need to use them.
For plotting an entire unsimplified dataset, the overhead of a
database will always be somewhat slower than a file streaming
from disk. Note that on good hardware with an well optimised
database even this difference can be minimised.
Cheers,
Brent Wood
--- On *Wed, 2/15/12, Stephen Woodbridge
/<wood...@swoodbridge.com<mailto:wood...@swoodbridge.com>>/*
wrote:
From: Stephen Woodbridge<wood...@swoodbridge.com
<mailto:wood...@swoodbridge.com>> Subject: Re: [postgis-users]
advice for quicker display? To:
postgis-users@postgis.refractions.net
<mailto:postgis-users@postgis.refractions.net> Date: Wednesday,
February 15, 2012, 8:14 AM
On 2/14/2012 1:57 PM, Bistrais, Bob wrote:
As some of you already know, I'm a newbie to PostGIS and have
just barely got a test PostGIS database up and running. So, my
latest question is in regards to draw times. I created a
statewide parcel layer from a shapefile. At statewide scale,
when the application loads, the parcel data draws far slower
than the original shapefile did. How can I tune this so that
draw times are better?
If you are drawing all the data, it will always be slower than
shapefiles. The trick is to not draw more than is reasonable at a
given scale. So the answer is don't try to draw all the parcels
for the whole state. As you zoom in and need to only draw a
subset of the parcels, you will start to get speed advantages by
using the spatial (GIST) indexes in postgis.
create index mytable_the_geom_gidx on mytable using gist
(the_geom);
-Steve W _______________________________________________
postgis-users mailing list postgis-users@postgis.refractions.net
<http://mc/compose?to=postgis-users@postgis.refractions.net>
http://postgis.refractions.net/mailman/listinfo/postgis-users
_______________________________________________ postgis-users
mailing list postgis-users@postgis.refractions.net
<mailto:postgis-users@postgis.refractions.net>
http://postgis.refractions.net/mailman/listinfo/postgis-users
-- Juan Marín Otero GIS Consultant
-------Visita mi blog en---------------------
http://guachintoneando.blogspot.com
---------------------------------------------------
_______________________________________________ postgis-users
mailing list postgis-users@postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
_______________________________________________ postgis-users
mailing list postgis-users@postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
_______________________________________________ postgis-users
mailing list postgis-users@postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
_______________________________________________
postgis-users mailing list
postgis-users@postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
_______________________________________________
postgis-users mailing list
postgis-users@postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
_______________________________________________
postgis-users mailing list
postgis-users@postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
