#1 Create a object with keyword datatype:
  Keywords : key1, key2
#2 update the object setting new keywords:
  Keywords : key1, key2updated
#3 run query:
mysql> select * from ezkeyword;
+----------+----+-------------+
| class_id | id | keyword     |
+----------+----+-------------+
|       16 |  1 | key1        |
|       16 |  2 | key2        |
|       16 |  3 | key1        |
|       16 |  4 | key2        |
|       16 |  5 | key1        |
|       16 |  6 | key2updated |
+----------+----+-------------+

Expected result should have been:
mysql> select * from ezkeyword;
+----------+----+-------------+
| class_id | id | keyword     |
+----------+----+-------------+
|       16 |  3 | key1        |
|       16 |  4 | key2updated  |
+----------+----+-------------+

( this is what happens if you do the same thing using admin2 interface )