[Qgis-developer] Postgis Caching - Enhancement

[Hugo Mercier]

Le 01/04/2014 10:45, Alex Mandel a écrit :
> This really applies to non-local data sources. Network latency can be
> huge issue, it can also be problematic if a bbox strategy isn't in use.
> You are right this is not Postgis specific. Database servers are more
> likely to be remote (shapefiles on a network share are a terrible idea
> in almost all cases). Maybe the recommendation is that people pipe
> Postgis through a WFS service when they want to use it this way? If I
> think about it that way WMS or WMTS would actually be a good way to get
> speed - but you can't really see attribute tables that way. Wonder if
> there's some way to hybridize it. Of course this assumes said users have
> the ability to setup such services in house quickly for new layers.
> 
> I've experienced this with DB tables from 1-100+ GB, it's not as big an
> issue with non DB (Oracle, MSSQL, etc) formats because they don't get as
> large. The problem is that most people forget to zoom in before turning
> on the layer, or if they need to see the whole extent the whole data is
> transferred before the renderer can simplify it. It's almost like a set
> of postgis views used similar to pyramids in rasters with simplification
> algorithms applied before transmission would be a way to handle it. Not
> QGIS specific but I could see a plugin in QGIS to build the views in
> Postgis.
> 
> Panning/Zooming requests data if the data isn't already cached. So if
> you start panning then go back to a spot you've been before you already
> have it.
> 
> I agree that always on caching is bad, hence my suggestion for a user
> toggle per layer. When doing cartography work you just need to be able
> work a little faster with the rendering for it to not be frustrating.
> Same for digitizing (assuming the postgis layer in question is reference).
> 

Hi,

I think caching is really a missing feature.
I like the idea if the user can turn it on/off and clear it easily
(keyboard shortcut like in a browser ?). For advanced users, maybe allow
to set the cache size.

-- 
Hugo Mercier
Oslandia