[postgis-users] advice for quicker display?

[pcreso at pcreso.com]

That is the name you are giving the index. It is good practice for the 
name to include the table & column(s) the index applies to in the 
name you give it.

--- On Wed, 2/15/12, Bistrais, Bob <Bob.Bistrais at maine.gov> wrote:

From: Bistrais, Bob <Bob.Bistrais at maine.gov>
Subject: Re: [postgis-users] advice for quicker display?
To: svm at clevelandmetroparks.com, "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
Date: Wednesday, February 15, 2012, 8:32 AM

OK, so it sounds like I need to create the index for starters (and not
bother with the layer at full scale).

As far as creating the index, is mytable_the_geom_gidx an existing
column, or the name of a new one? 


-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
Stephen V. Mather
Sent: Tuesday, February 14, 2012 2:26 PM
To: 'PostGIS Users Discussion'
Subject: Re: [postgis-users] advice for quicker display?

To expand on that, the basic understanding is that file level access to
data
(e.g. shapefile) will always be faster for the entire dataset (all
things
being equal) because of the management overhead of the database, but for
accessing a subset of features of the dataset (often the typical use
case),
the database is faster if it has indices on the appropriate columns (the
geometry being the more important one).  Even if you are accessing all
of
the records in the database at once as a common case, you probably don't
need every node in the polygons/polylines, and might create a view or
column
that pre-generalizes those data before delivering them.

Best,
Steve

Stephen Mather
Geographic Information Systems (GIS) Manager
(216) 635-3243
svm at clevelandmetroparks.com
clevelandmetroparks.com




-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
Stephen
Woodbridge
Sent: Tuesday, February 14, 2012 2:15 PM
To: postgis-users at postgis.refractions.net
Subject: Re: [postgis-users] advice for quicker display?

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
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