ALTER TABLE didn't remember the exact

geometry type (POINT, LINESTRING, etc)
and changed all into "GEOMETRY".

mysql-test/r/gis.result

@@ -355,3 +355,36 @@ first	second	w	c	o	e	d	t	i	r
 121	120	0	0	1	0	0	0	1	0
 121	121	1	1	0	1	0	0	1	0
 DROP TABLE pt, ls, p, mpt, mls, mp, gc, geo;
+CREATE TABLE g1 (
+pt  point,
+ln  linestring,
+pg  polygon,
+mpt multipoint,
+mln multilinestring,
+mpg multipolygon,
+gc  geometrycollection,
+gm  geometry
+);
+SHOW FIELDS FROM g1;
+Field	Type	Collation	Null	Key	Default	Extra
+pt	point	binary	YES		NULL	
+ln	linestring	binary	YES		NULL	
+pg	polygon	binary	YES		NULL	
+mpt	multipoint	binary	YES		NULL	
+mln	multilinestring	binary	YES		NULL	
+mpg	multipolygon	binary	YES		NULL	
+gc	geometrycollection	binary	YES		NULL	
+gm	geometry	binary	YES		NULL	
+ALTER TABLE g1 ADD fid INT NOT NULL;
+SHOW FIELDS FROM g1;
+Field	Type	Collation	Null	Key	Default	Extra
+pt	point	binary	YES		NULL	
+ln	linestring	binary	YES		NULL	
+pg	polygon	binary	YES		NULL	
+mpt	multipoint	binary	YES		NULL	
+mln	multilinestring	binary	YES		NULL	
+mpg	multipolygon	binary	YES		NULL	
+gc	geometrycollection	binary	YES		NULL	
+gm	geometry	binary	YES		NULL	
+fid	int(11)	binary			0	
+DROP TABLE g1;

mysql-test/t/gis.test

@@ -121,3 +121,22 @@ Intersects(g1.g, g2.g) as i, Crosses(g1.g, g2.g) as r
 FROM gc g1, gc g2 ORDER BY first, second;
 
 DROP TABLE pt, ls, p, mpt, mls, mp, gc, geo;
+
+#
+# Check that ALTER TABLE doesn't loose geometry type
+#
+CREATE TABLE g1 (
+  pt  point,
+  ln  linestring,
+  pg  polygon,
+  mpt multipoint,
+  mln multilinestring,
+  mpg multipolygon,
+  gc  geometrycollection,
+  gm  geometry
+);
+
+SHOW FIELDS FROM g1;
+ALTER TABLE g1 ADD fid INT NOT NULL;
+SHOW FIELDS FROM g1;
+DROP TABLE g1;

sql/field.cc

@@ -5475,4 +5475,8 @@ create_field::create_field(Field *old_field,Field *orig_field)
       def=new Item_string(pos,tmp.length(), charset);
     }
   }
+  if (sql_type == FIELD_TYPE_GEOMETRY)
+  {
+    geom_type= ((Field_geom*)old_field)->geom_type;
+  }
 }