Bug #39737 Assignment operator does not allocate memory for spatial variables

Description:

for example,

lets say  g1 & g2 are of type GEOMETRY.

then set g1 = g2 does not allocate new memory to g1 & copy the value of g2.
instead it points to the value at g1

 

How to repeat:
DELIMITER $$
CREATE PROCEDURE TEST()
BEGIN
	DECLARE P1, P2 POINT;

	SET P1 = GeomFromText('POINT( 10 10)');
	SET P2 = P1;
        SELECT ' Both P1 and P2 should be identical:', ASTEXT(P1), ASTEXT(P2);

	SET P1 = GeomFromText('POINT( 20 20)');

        SELECT 'P1 and P2 should differ', ASTEXT(P1), ASTEXT(P2);
END;
$$
DELIMITER ;
CALL TEST();

Suggested fix:
I think assignment operator should alloc new memory to LHS variable

Verified with 5.1.28:

C:\Program Files\MySQL\MySQL Server 5.0\bin>mysql -uroot -proot -P3310 test
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.1.28-rc-community MySQL Community Server (GPL)

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> drop procedure test;
ERROR 1305 (42000): PROCEDURE test.test does not exist
mysql> DELIMITER $$
mysql> CREATE PROCEDURE TEST()
    -> BEGIN
    ->  DECLARE P1, P2 POINT;
    ->
    ->  SET P1 = GeomFromText('POINT( 10 10)');
    ->  SET P2 = P1;
    ->         SELECT ' Both P1 and P2 should be identical:', ASTEXT(P1), ASTEXT
(P2);
    ->
    ->  SET P1 = GeomFromText('POINT( 20 20)');
    ->
    ->         SELECT 'P1 and P2 should differ', ASTEXT(P1), ASTEXT(P2);
    -> END;
    -> $$
Query OK, 0 rows affected (0.30 sec)

mysql> DELIMITER ;
mysql> CALL TEST();
+--------------------------------------+--------------+--------------+
| Both P1 and P2 should be identical:  | ASTEXT(P1)   | ASTEXT(P2)   |
+--------------------------------------+--------------+--------------+
|  Both P1 and P2 should be identical: | POINT(10 10) | POINT(10 10) |
+--------------------------------------+--------------+--------------+
1 row in set (0.06 sec)

+-------------------------+--------------+--------------+
| P1 and P2 should differ | ASTEXT(P1)   | ASTEXT(P2)   |
+-------------------------+--------------+--------------+
| P1 and P2 should differ | POINT(20 20) | POINT(20 20) |
+-------------------------+--------------+--------------+
1 row in set (0.08 sec)

Query OK, 0 rows affected (0.08 sec)

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/71929

2870 Alexey Botchkov	2009-04-13
      Bug#39737      Assignment operator does not allocate memory for spatial variables
         GEOMETRY fields should be handled like blobs when they're copied.
      
      per-file messages:
        mysql-test/r/gis.result
      Bug#39737      Assignment operator does not allocate memory for spatial variables
          test result
        mysql-test/t/gis.test
      Bug#39737      Assignment operator does not allocate memory for spatial variables
          test case
        sql/field_conv.cc
      Bug#39737      Assignment operator does not allocate memory for spatial variables
          to->type() == MYSQL_TYPE_GEOMETRY checks added