[postgis-tickets] [PostGIS] #3457: When a geometry is smaller than a raster but their extents are the same, one of the overloads of ST_Clip doesn't give expected output

[PostGIS]

#3457: When a geometry is smaller than a raster but their extents are the same,
one of the overloads of ST_Clip doesn't give expected output
-----------------------+---------------------------
  Reporter:  GMudambi  |      Owner:  Bborie Park
      Type:  defect    |     Status:  new
  Priority:  critical  |  Milestone:  PostGIS 2.4.6
 Component:  raster    |    Version:  2.1.x
Resolution:            |   Keywords:
-----------------------+---------------------------

Comment (by saibot):

 Dear Jiří, users and developers,

 the st_clip function works incorrectly. I strongly recommend the following
 correction to all users. I hope that the bug will be fixed soon.

 {{{
 CREATE OR REPLACE FUNCTION public.st_clip(
   rast      RASTER, nband INTEGER [], geom GEOMETRY,
   nodataval DOUBLE PRECISION [] DEFAULT NULL :: DOUBLE PRECISION [],
   crop      BOOLEAN DEFAULT TRUE)
   RETURNS RASTER AS
 $BODY$
 BEGIN

 -- wrong version
   -- short-cut if geometry's extent fully contains raster's extent
   -- IF (nodataval IS NULL OR array_length(nodataval, 1) < 1) AND geom ~
 ST_Envelope(rast)
 -- corrected version (bug-fix)
   -- no more short-cut!!!  if geometry's extent fully contains raster's
 extent
   IF (nodataval IS NULL OR array_length(nodataval, 1) < 1) AND
 st_contains(geom, ST_Envelope(rast))
   THEN RETURN rast;
   END IF;

   RETURN PUBLIC._ST_Clip($1, $2, $3, $4, $5);
 END;
 $BODY$
 LANGUAGE plpgsql
 IMMUTABLE
 COST 100;
 }}}

 Thank you for all your work and best regards,

 Sai-bot

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3457#comment:8>
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