Hi all, I am *guessing* that Manifold is using the .NET Dataset type to cache data, and that some kind of db manager takes care of the sync.
SQLAlchemy could be used in a python plugin for the same purpose. Best, Angelos On Tue, Aug 6, 2013 at 9:46 AM, Marco Hugentobler < [email protected]> wrote: > 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]> <[email protected]> > *To:* Willem Buitendyk <[email protected]> <[email protected]> > *Cc:* qgis-user <[email protected]> <[email protected]>; > "[email protected]" <[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]> 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 > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user > > > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user > > > > > _______________________________________________ > Qgis-developer mailing > [email protected]http://lists.osgeo.org/mailman/listinfo/qgis-developer > > > > -- > Dr. Marco Hugentobler > Sourcepole - Linux & Open Source Solutions > Weberstrasse 5, CH-8004 Zürich, [email protected] > http://www.sourcepole.ch > Technical Advisor QGIS Project Steering Committee > > > _______________________________________________ > Qgis-developer mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-developer > > -- Angelos Tzotsos Remote Sensing Laboratory National Technical University of Athens http://users.ntua.gr/tzotsos
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