[postgis-users] Performance compared to large shapefiles?

[Paul Ramsey]

It depends a lot on your use case. If you're rendering thousands of  
features, that's just going to take a lot of time, shape file or  
postgis. You might find that for really large tables the postgis  
index is balanced better than the shape quadtree, and that provides  
some performance boost. But always, you have to be drawing a  
managable subset.

The 10% figure is quite old, and was a single-threaded test on the  
old postgis geometries. Some folks have told me that for concurrent  
access PostGIS is actually faster than shape files. But frankly, we  
are missing any kind of real benchmark at this point. You just have  
to try yourself and see.

Paul

On 25-Apr-07, at 7:46 AM, Jeff Dege wrote:

> 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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