I have two large layers that I want to do intersect operations. One is municipalities and the other is landuse. Right now, the landuse layer is of MultiPolygon type that is, for the entire state, I have only one entry in the table with the class "Forest", but composed of several small polygons.
If I wanted to find all the forest areas in my city, what would be more efficient in PostGIS:
- Do an intersect between my municipality and the FOREST multipolygon that takes up the entire state or,
- Convert the Forest multipolygon into a new layer with several polygons and then do the Intersect
My gut feeling is that if I break the multipolygon feature into single polygons, the intersect might be faster because it would only occur in the polygons that have a bounding box that overlaps my municipality. If I have multipolygon features, the intersect would have to go through the entire state to identify only the parts that fall inside the municipality.
This is more or less what I'm trying yo get. I want the light green polygons.
Does it matter it the forest polygons (F) are stored as multipolygons or singlepolygons?
I'm going to be processing a very large dataset (Amazon)