[Qgis-developer] Spatial index - what about having it automatically created and updated ?

kimaidou kimaidou at gmail.com
Thu Feb 27 01:47:26 PST 2014

Hi list,

I have some concerns about spatial indexes in QGIS. Spatial indexes are
very usefull, and for me rather mandatory as soon as you deal with more
than 100 features.

I would like to share some ideas about them :

1) Extend QGIS so that it can create spatial indexes for more vector
format. If I am correct, for now only Shapefiles and Database vector layers
can have a spatial index created by QGIS . Why not for GeoJson, CSV files,
etc ?

2) If possible, create a spatial index for each vector layer added to the
canvas if no one is already present. Since it is a quite fast operation,
the small time needed is worth it.

3) If possible, update the spatial index (replace the old qix by a new one)
every time the vector layer is updated. No need to do so for database
layers, but this can be very usefull for big shapefiles. I have seen some
people creating a spatial index, then as time passes, they add more and
more data into the shapefile but forget to update the spatial index.
Sometimes this can lead to some data not displayed in QGIS because QGIs
seems to rely on the outdatedSpatial index.

For me, using spatial indexes is like brushing my teeth : I do it very
often without even thinking of it. But many users do not know that spatial
indexes exists, or do it but forget to use them as needed. I really think
QGIS should help them to improve perfs in the background.

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