[postgis-devel] Faster ST_Intersection

[Darafei "Komяpa" Praliaskouski]

Hi,

I have two polygonal layers to intersect and need to measure area of
intersections.

ST_Area(ST_Intersection(a.geom, b.geom)) works fine, but is rather slow.
Typical polygon on first side has <10 edges, on second 200..1000 edges.

What are my options to make it faster? Any ideas, links, experiences to
share are welcome.

For starters, this seems to work faster than vanilla ST_Intersection in my
case:

create or replace function clipped_st_intersection(geom1 geometry,
geom2 geometry)
  returns geometry
as $$select ST_Intersection(
              case
                when ST_MemSize(geom1) > 160 then ST_ClipByBox2D(geom1, geom2)
                else geom1 end, case
                when ST_MemSize(geom2) > 160 then ST_ClipByBox2D(geom2, geom1)
                else geom2 end)$$
language sql
immutable
strict
parallel safe;

-- 
Darafei Praliaskouski
Support me: http://patreon.com/komzpa
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