[PostGIS] #5953: Slow st_intersection with big input polygons

[PostGIS]

#5953: Slow st_intersection with big input polygons
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  Reporter:  Lars Aksel Opsahl  |      Owner:  pramsey
      Type:  enhancement        |     Status:  new
  Priority:  medium             |  Milestone:  PostGIS 3.6.0
 Component:  postgis            |    Version:  master
Resolution:                     |   Keywords:
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Comment (by mdavis):

 My take on this is:

 Running intersections against the subdivided polygon is faster than
 against the whole polygon because there many subpolygons are eliminated
 from processing (by the intersects filter), and the subpolygons are much
 smaller than the original polygon.

 The test against the polygon with holes removed isn't apples-to-apples,
 since it runs `ST_BuildArea` and `ST_Boundary`.  These might be taking
 significant time.  Materializing the boundary polygon in a separate table
 would reveal if this is the cause of the slowdown.

 Unlike `ST_Intersects`, `ST_Intersection` has no "prepared mode", so it
 has to compute using the entire input on each call.  Using `ST_Subdivide`
 is a way around this.  If all you need is the area of intersection,
 developing a workflow using this technique could be the way to go.
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5953#comment:2>
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