[postgis-users] Performance compared to large shapefiles?

[Pedro Doria Meunier]

Hey Jeff,

The short answer is YES! You can!

Speeding up is a matter of creating the relevant indices.
You can have as much data as 3TB per table so you don't have to split your
data.

This, however, requires clever planning... ;-)

One thing you can count for certain is that given the proper indices being
used and good SQL code is that pgsql/postgis is **fast** retrieving the
results...
I use this combination for our Fleet Management Solution for over a year now
and it's proven to be a rock-solid, stable and **fast** approach.

To give you some comparative data:

For a layer containing 500K+ features (roads) results are given usually
under 50ms. And we're talking about queries with reprojection on-the-fly
plus distance calculations... ;-)

HTH,
Pedro.

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Jeff
Dege
Sent: quarta-feira, 25 de Abril de 2007 15:46
To: postgis-users at postgis.refractions.net
Subject: [postgis-users] Performance compared to large shapefiles?

Someone pointed me to PostGIS as being a tool worth considering.

We've done our mapping so far with various extensions built on top of
UMN MapServer (ka-map and openlayers).  The GIS data we've been storing
in shapfiles.

We're finding it very difficult to manage acceptable performance when
working with large shapefiles, where large means >500MB, >3 million
features.  We've been splitting these both by feature type (pulling the
features we display at wider zooms into separate files) and by geography
(tiling).  It's tedious, time-consuming, and performance still isn't
what we'd wish.

The docs for PostGIS say that we can expect access times to be about 10%
greater than working with shapefiles, due to the overhead of
establishing a database, etc.

Is this constant?

What I'd like to be true is that PostGIS would offer indexing
possibilities that would allow for faster access to subsets of large
sets of geographic data than we're getting with shapefiles.

But what I'd like to be true isn't always the case.

Can I accomplish the sort of speedups I'm getting by splitting up
shapefiles, within PostGIS, without the expense of splitting up
shapefiles?

Can I do better?

Thanks.
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