Bug#28763: Selecting geometry fields in UNION caused server crash.

This bug was introduced by the fix for the bug#27300. In this fix a section
of code was added to the Item::tmp_table_field_from_field_type method.
This section intended to create Field_geom fields for the Item_geometry_func
class and its descendants. In order to get the geometry type of the current
item it casted "this" to the Item_geometry_func* type. But the
Item::tmp_table_field_from_field_type method is also used for creation of
fields for UNION and in this case this method is called for an object of the
Item_type_holder class and the cast to the Item_geometry_func* type causes 
a server crash.

Now the Item::tmp_table_field_from_field_type method correctly works when it's
called for both the Item_type_holder and the Item_geometry_func classes.
The new geometry_type variable is added to the Item_type_holder class.
The new method called get_geometry_type is added to the Item_field
and the Field classes. It returns geometry type from the field for the
Item_field and the Field_geom classes and fails an assert for other Field
descendants.

mysql-test/r/gis.result

@@ -864,4 +864,25 @@ SELECT Overlaps(@horiz1, @point2) FROM DUAL;
 Overlaps(@horiz1, @point2)
 0
 DROP TABLE t1;
+create table t1(f1 geometry, f2 point, f3 linestring);
+select f1 from t1 union select f1 from t1;
+f1
+insert into t1 (f2,f3) values (GeomFromText('POINT(1 1)'),
+GeomFromText('LINESTRING(0 0,1 1,2 2)'));
+select AsText(f2),AsText(f3) from t1;
+AsText(f2)	AsText(f3)
+POINT(1 1)	LINESTRING(0 0,1 1,2 2)
+select AsText(a) from (select f2 as a from t1 union select f3 from t1) t;
+AsText(a)
+POINT(1 1)
+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	
+select AsText(a) from t2;
+AsText(a)
+POINT(1 1)
+LINESTRING(0 0,1 1,2 2)
+drop table t1, t2;
 End of 5.0 tests

mysql-test/t/gis.test

@@ -557,4 +557,17 @@ SELECT Overlaps(@horiz1, @point2) FROM DUAL;
 
 DROP TABLE t1;
 
+#
+# Bug#28763: Selecting geometry fields in UNION caused server crash.
+#
+create table t1(f1 geometry, f2 point, f3 linestring);
+select f1 from t1 union select f1 from t1;
+insert into t1 (f2,f3) values (GeomFromText('POINT(1 1)'),
+  GeomFromText('LINESTRING(0 0,1 1,2 2)'));
+select AsText(f2),AsText(f3) from t1;
+select AsText(a) from (select f2 as a from t1 union select f3 from t1) t;
+create table t2 as select f2 as a from t1 union select f3 from t1;
+desc t2;
+select AsText(a) from t2; 
+drop table t1, t2;
 --echo End of 5.0 tests

sql/field.h

@@ -360,7 +360,11 @@ public:
   {
     return field_length / charset()->mbmaxlen;
   }
-
+  virtual geometry_type get_geometry_type()
+  {
+    /* shouldn't get here. */
+    DBUG_ASSERT(0);
+  }
   friend bool reopen_table(THD *,struct st_table *,bool);
   friend int cre_myisam(my_string name, register TABLE *form, uint options,
 			ulonglong auto_increment_value);
@@ -1325,6 +1329,7 @@ public:
   uint get_key_image(char *buff,uint length,imagetype type);
   uint size_of() const { return sizeof(*this); }
   int  reset(void) { return !maybe_null() || Field_blob::reset(); }
+  geometry_type get_geometry_type() { return geom_type; };
 };
 #endif /*HAVE_SPATIAL*/
 

sql/item.cc

@@ -4317,7 +4317,9 @@ Field *Item::tmp_table_field_from_field_type(TABLE *table)
   case MYSQL_TYPE_GEOMETRY:
     return new Field_geom(max_length, maybe_null, name, table,
                           (Field::geometry_type)
-                          ((Item_geometry_func *)this)->get_geometry_type());
+                          ((type() == Item::TYPE_HOLDER) ?
+                           ((Item_type_holder *)this)->get_geometry_type() :
+                           ((Item_geometry_func *)this)->get_geometry_type()));
   }
 }
 
@@ -6422,6 +6424,10 @@ Item_type_holder::Item_type_holder(THD *thd, Item *item)
   if (Field::result_merge_type(fld_type) == INT_RESULT)
     decimals= 0;
   prev_decimal_int_part= item->decimal_int_part();
+  if (item->field_type() == MYSQL_TYPE_GEOMETRY)
+    geometry_type= (item->type() == Item::FIELD_ITEM) ?
+      ((Item_field *)item)->get_geometry_type() :
+      (Field::geometry_type)((Item_geometry_func *)item)->get_geometry_type();
 }
 
 

sql/item.h

@@ -1304,6 +1304,11 @@ public:
   int fix_outer_field(THD *thd, Field **field, Item **reference);
   virtual Item *update_value_transformer(byte *select_arg);
   void print(String *str);
+  Field::geometry_type get_geometry_type()
+  {
+    DBUG_ASSERT(field_type() == MYSQL_TYPE_GEOMETRY);
+    return field->get_geometry_type();
+  }
   friend class Item_default_value;
   friend class Item_insert_value;
   friend class st_select_lex_unit;
@@ -2563,6 +2568,7 @@ class Item_type_holder: public Item
 protected:
   TYPELIB *enum_set_typelib;
   enum_field_types fld_type;
+  Field::geometry_type geometry_type;
 
   void get_full_info(Item *item);
 
@@ -2582,6 +2588,7 @@ public:
   Field *make_field_by_type(TABLE *table);
   static uint32 display_length(Item *item);
   static enum_field_types get_real_type(Item *);
+  Field::geometry_type get_geometry_type() { return geometry_type; };
 };