[Qgis-developer] [Qgis-user] Caching remote postgis layers?

[Brent Wood]

Hi Willem,

Why can you not save such a layer or a selection from such a layer, as a local shapefile (or other supported format). is this not effectively a "local cache"? Delete/overwrite when you desire.


Where is the performance bottleneck? Postgis, network, QGIS?  Just creating a local cache will not necessarily speed things up, if your database is on a fast server with a fast network, it may even get slower.


Sourcepole have developed (for NIWA, New Zealand) a plugin that supports local caching of WMS & WFS data sources. This could probably be adapted to support other input formats. Marco Hugentobler did the coding for this - he can perhaps comment?

As Nathan says, caching a local snapshot of a dynamic, multi-user database will result in something that gets out of sybc with the source pretty quickly. Caching a local copy of a largely static database is relatively safe.

Cheers

Brent


________________________________
 From: Nathan Woodrow <madmanwoo at gmail.com>
To: Willem Buitendyk <willem at pcfish.ca> 
Cc: qgis-user <qgis-user at lists.osgeo.org>; "qgis-developer at lists.osgeo.org" <qgis-developer at lists.osgeo.org> 
Sent: Tuesday, August 6, 2013 11:07 AM
Subject: Re: [Qgis-user] Caching remote postgis layers?
 


Hey Willem,

I'm not aware of a feature like that.  The best place to ask this question to see if anyone is working, or planning to work, on it is the developer list.  I have copied it in so it show up there too.

Caching could be done by storing the returned results in a memory spatialite database. The tricky thing is knowing when to get any new results from the postgis database when things have changed on the database.  How does Manifold handling viewing an area, updating something using SQL on the database (not though Manifold) and then looking at that area again?

- Nathan 



On Tue, Aug 6, 2013 at 2:44 AM, Willem Buitendyk <willem at pcfish.ca> wrote:

I've noticed looking at the roadmap that caching remote postgis data is not on the list.  I love qgis but a lot of my work involves connecting to a remote postgis database.  The speed of navigating a large dataset is, at the moment, rather unbearable.  I also use Manifold GIS and the difference in speed is shocking, presumably because Manifold is caching the dataset.  This seems like it should be a relatively easy thing to implement.  Is there interest on this board for this feature?  I was thinking at taking a stab at contributing to the source code but am wondering about methods to achieve data caching most efficiently.  Look forward to others thoughts?  Or maybe I missing something that is already in place?
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