[postgis-tickets] [PostGIS] #4530: upgrade postgis 2.3 to postgis 3.0.0rc1 fails at raster

[PostGIS]

#4530: upgrade postgis 2.3 to postgis 3.0.0rc1 fails at raster
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  Reporter:  robe                   |      Owner:  strk
      Type:  defect                 |     Status:  new
  Priority:  medium                 |  Milestone:  PostGIS 3.0.1
 Component:  build/upgrade/install  |    Version:  trunk
Resolution:                         |   Keywords:
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Comment (by strk):

 I think it's a legit failure. The code at hand is
 raster/rt_pg/rtpostgis.sql.in around line 7490.
 Function _add_raster_constraint_extent(rastschema name, rasttable name,
 rastcolumn name).
 The offending "null argument to EXECUTE" comes from here:

     sql := 'SELECT @extschema at .st_ashexewkb( @extschema at .st_setsrid(
 @extschema at .st_extent( @extschema at .st_envelope('
       || quote_ident($3)
       || ')), ' || srid || ')) FROM '
       || fqtn;
     EXECUTE sql INTO attr;


 I bet {{{ srid }}} is the null value, propagating to the whole {{{ sql
 }}}. Here's how it is fetched:

     sql := 'SELECT @extschema at .ST_SRID('
       || quote_ident($3)
       || ') FROM '
       || fqtn
       || ' WHERE '
       || quote_ident($3)
       || ' IS NOT NULL LIMIT 1;';
                 EXECUTE sql INTO srid;


 Now.. what if the raster table is empty ? I guess SRID remains NULL,
 making a NULL sql and getting to the error. I'd rather fix than comment
 out.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/4530#comment:3>
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