MDEV-4922 Stored Procedure - Geometry parameter not working.

  Fhe GEOMETRY field should be handled just as the BLOB field. So that was fiexed in field_conv.
  One additional bug was found and fixed meanwhile - thet the geometry field subtypes
  should also be merged for UNION command.

mysql-test/r/gis.result

@@ -934,7 +934,7 @@ LINESTRING(0 0,1 1,2 2)
 create table t2 as select f2 as a from t1 union select f3 from t1;
 desc t2;
 Field	Type	Null	Key	Default	Extra
-a	point	YES		NULL	
+a	geometry	YES		NULL	
 select AsText(a) from t2;
 AsText(a)
 POINT(1 1)

sql/field.cc

@@ -7629,6 +7629,14 @@ int Field_geom::store(const char *from, uint length, CHARSET_INFO *cs)
   return -1;
 }
 
+Field::geometry_type Field_geom::geometry_type_merge(geometry_type a,
+                                                            geometry_type b)
+{
+  if (a == b)
+    return a;
+  return Field::GEOM_GEOMETRY;
+}
+
 #endif /*HAVE_SPATIAL*/
 
 /****************************************************************************

sql/field.h

@@ -1998,6 +1998,7 @@ class Field_geom :public Field_blob {
   int reset(void) { return Field_blob::reset() || !maybe_null(); }
 
   geometry_type get_geometry_type() { return geom_type; };
+  static geometry_type geometry_type_merge(geometry_type, geometry_type);
 };
 #endif /*HAVE_SPATIAL*/
 

sql/field_conv.cc

@@ -828,8 +828,9 @@ Copy_field::get_copy_func(Field *to,Field *from)
 
 int field_conv(Field *to,Field *from)
 {
+  bool blob_type_dest= to->flags & BLOB_FLAG;
   if (to->real_type() == from->real_type() &&
-      !(to->type() == MYSQL_TYPE_BLOB && to->table->copy_blobs))
+      !(blob_type_dest && to->table->copy_blobs))
   {
     if (to->pack_length() == from->pack_length() &&
         !(to->flags & UNSIGNED_FLAG && !(from->flags & UNSIGNED_FLAG)) &&
@@ -858,7 +859,7 @@ int field_conv(Field *to,Field *from)
       return 0;
     }
   }
-  if (to->type() == MYSQL_TYPE_BLOB)
+  if (blob_type_dest)
   {						// Be sure the value is stored
     Field_blob *blob=(Field_blob*) to;
     from->val_str(&blob->value);

sql/item.cc

@@ -9486,6 +9486,11 @@ bool Item_type_holder::join_types(THD *thd, Item *item)
       item_decimals= 0;
     decimals= max(decimals, item_decimals);
   }
+
+  if (fld_type == FIELD_TYPE_GEOMETRY)
+    geometry_type=
+      Field_geom::geometry_type_merge(geometry_type, item->get_geometry_type());
+
   if (Field::result_merge_type(fld_type) == DECIMAL_RESULT)
   {
     decimals= min(max(decimals, item->decimals), DECIMAL_MAX_SCALE);