Support keyword substitution in provider queries

[qgib]

Author Name: Sandro Santilli (@strk)
Original Redmine Issue: 4374

Redmine category:data_provider

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When fetching features from a query it would be useful to allow using keywords to be substituted on each fetching.
Such keywords, in particular pixel sizes and extent, could be used by the query to preprocess geometries (like DP-simplification, grid snapping etc.) and reduce the amount of geometries fetched (using extent information).

[qgib]

Author Name: Paolo Cavallini (@pcav)

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• category_id was configured as Data Provider

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• fixed_version_id was configured as Version 1.7.4

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• fixed_version_id was changed from Version 1.7.4 to Version 2.0.0

[qgib]

Author Name: Pirmin Kalberer (Pirmin Kalberer)

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• fixed_version_id was changed from Version 2.0.0 to Future Release - Nice to have

[qgib]

Author Name: Andreas Wicht (@andywicht)

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That would be a great change in order to make actual use of the postgis_topology in QGIS. For tiny topologies it would not make much of a difference, but for the bigger ones.
Big topologies are completely un-editable in QGIS due to the restriction that spatial indexing is not compatible with the TopoGeometry type.
So, given the fact, that a table additionally stores the Geometry representation of a TopoGeometry, the Geometry column could be used to query the spatial extents and therefore utilising spatial indexing while displaying and editing the TopoGeometry column.

That would enable anybody to utilise QGIS for the editing process of large postgis topologies as no custom web-gis solutions would have to be developed.

Reconsidering the target version would be highly appreciated by me :-)

[qgib]

Author Name: Sandro Santilli (@strk)

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I guess "target version" could be changed if someone provides an actual patchset to implement the keyword substitution.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• easy_fix was configured as 0

[strk]

One problem with keyword substitution is that attributes fetching would then end up depending on current extent (unless we have the substitution pass an "universe" bounding box in that case)

[strk]

@andywicht could you please take a look at #31468 ?