[QGIS-Developer] QGIS virtual layer incredibly slow

[Hugo Mercier]

Hi,

Sorry for the delay.

In the case of ST_Intersects, which is symmetric, there is no particular
order to follow. Both orders should work.

where st_intersects(lie.geometry, tbap.Geometry) AND lie._search_frame_
= tbap.geometry means:

"for each geometry of tbap, compute its bounding box, select only
geometries of 'lie' that are inside this box and then test for the
actual intersection"

Inverting lie and tbap would not change the result (and not even
performances I think)

On 31/03/2020 18:45, snaileater wrote:
> Hugo,
> 
> sorry for posting so late but i have the following question after this
> exchange :
> 
> when it come to 'order' the operators why do u advise to write
>  
> *lie._search_frame_ = tbap.geometry* and not :
> 
> /tbap._search_frame_ =lie.geometry/
> 
> What is the logic behind this syntax ?
> 
> Thanks !
> 
> 
> 
> --
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