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Following on this question.

I have a set of reference lines and a non geometrical table of events. This table contains the mileage of the event along the reference lines, amongst other attributes.

I upscaled my application to use real world data. It works, but the display is slow. I have read about spatial indexes, but I am not sure about how to make it work with a non spatial table.

My virtual layer query is the following :

SELECT
    e.fid /*:int*/,
    e.'LE_idRiver' AS RouteID /*:int*/, 
    r.'LB_idRiver' AS RivName /*:text*/,
    e.'LE_Value' AS val /*:int*/,
    ST_Line_Substring(r.geometry, e.'LE_FROM' / st_length(r.geometry), e.'LE_TO' / st_length(r.geometry)) as geom /*:linestring:2056*/
FROM  "Linear_events"as e
Join    "base_lines" as r ON (e.'LE_idRiver' = r.'fid') 

The baselines are quite long (up to 50km) and some events are short (~10m), so there are quite a few of them. I was thinking about splitting the baselines every km and use the processes described here but I would rather have a single geometry if possible.

Moreover, my hypothesis is that the whole layer is redrawn even when I zoom in, meaning that this approach would lead to an improvement at a lower scale, but the gains would vanish at a larger scale, leaving the problem unsolved.

Is there a way to improve the display speed of my layer at all zoom levels in this use case?

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