Hi Willem
Another thing to explore is the offline editing plugin. It caches
postgis layers to a local spatialite database and can even be used to
synchronise edits between local spatialite db and remote postgis db.
>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?
The plugin saves WMS as local rasters and WFS as local vectors. This is
similar to save as local vector / raster file by hand. However the
plugin is more convenient because it manages the local storage and the
reference to the remote uri. It has some other nice features like
synchronizing / offlining in a graphical way. Btw., we hope to include
this plugin (a C++ one) into the main repository after 2.0 feature
freeze is over.
Regards,
Marco
On 06.08.2013 03:20, Brent Wood wrote:
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 <[email protected]>
*To:* Willem Buitendyk <[email protected]>
*Cc:* qgis-user <[email protected]>;
"[email protected]" <[email protected]>
*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 <[email protected]
<mailto:[email protected]>> 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?
Willem
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--
Dr. Marco Hugentobler
Sourcepole - Linux & Open Source Solutions
Weberstrasse 5, CH-8004 Zürich, Switzerland
[email protected] http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee
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