[postgis-users] Difference between ST_Intersects and && operator

[Andreas Forø Tollefsen]

Hi all.
I am working on a huge vector grid project where i need to intersect country
polygon data and vector grid cells.
For this i need to first select the grid cells which intersects with the
country polygons.

SELECT DISTINCT testgrid.gid, xcoord, ycoord, cell INTO testgrid2 FROM
testgrid, cshaperef WHERE ST_Intersects(cshaperef.the_geom,
testgrid.cell)=true

I tried both the ST_Intersects and the && operator, but i cannot really
understand the difference.
After looking at my results the ST_Intersects gave exactly the cells which
intersected with the country polygons, while the && gave many additional
cells.
Another interesting observation is the the && is way faster than the
ST_Intersects which in my case 188 polygons and 212000 cells takes a lot of
time.

Could anyone please elaborate on the difference?
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