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I've to create a spatial intersection of two tables (poly_a and poly_b) containing polygon features. Is there any way to remove unexpected linestring results?

CREATE VIEW poly_intersection AS SELECT
row_number() over() AS gid,
subquery.*
FROM
    (SELECT
    (ST_Dump(ST_Intersection(poly_a.geom, poly_b.geom))).geom::geometry(polygon, 4326)
    FROM poly_a, poly_b
    WHERE ST_Intersects(poly_a.geom, poly_b.geom) AND NOT ST_Touches(poly_a.geom, poly_b.geom)
    ) AS subquery;

enter image description here

ERROR:  Geometry type (LineString) does not match column type (Polygon)

I'm wondering about the line geometries because of using AND NOT ST_Touches(poly_a.geom, poly_b.geom) in the WHERE clause.

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Yes, use ST_CollectionExtract to pull only the polygonal parts out of the intersection output.

  • Shouldn't AND NOT ST_Touches(poly_a.geom, poly_b.geom) do this? – Lunar Sea Mar 5 '16 at 21:51
  • Dimensional collapse during overlay could be causing slight overlaps to turn into boundary touches. Dunno, guessing. Perfection is not available :) – Paul Ramsey Mar 6 '16 at 22:05

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