[Qgis-user] Qgis/qgis server different layer scales to speed up server

[Pietro Rossin]

Hello qgis users
I hope this is the right place to ask for help in selecting the right
strategy to spped up the data served by qgis-server/lizmap

I have many polygonal features that can be seen at various zoom level
I want to serve them as a webis with qgis-server and Lizmap
Data are on a postgis server with all indexes set.

I had some suggestion to simplify the geometry let's say with 3-4
simplyfication level on the nodes of any polygon.
So I made 3 geometry column (orig - simpl1, simpl2 ecc) all the same kind of
the original one and each field with its index.
In simpl1, 2 3 ecc I calculate a simplification with
ST_SimplifyPreserveTopology(geometry , float) with increasing tolerance
based on original geometry.

Now I will like to use these geometry columns to load simpler features at
low zoom and richer ones at higher zoom level.

Is it possible to tell qgis to load a particular geometry column based on
the zoom level?
This thing should be also available in qgis-server and then in lizmap..

One solution I found was to make different view/query to load layers with
the desired geometry column and use visibility based on scale to show/hide
different layers..

Any other way?

Is it preferable to create views in Postgis or to query data by qgis db
manager?

Thanks for your help
Pietro




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