thank you for the clarification.
the reason why i asked is because if jboss uses horizontal partitioning, is it possible for the same id to be used for different objects in different tables?
for example, given the following tables:
BASE
-oid
-name
EXTENDED
-oid
-name
-age
if in BASE, the following record exists:
BASE
oid | name
---|-----
1 | marc
and we want to add a new record (entity instance having different data) to EXTENDED, does jboss know not to use an oid of "1" in EXTENDED, since it already exists in the BASE table?
also, how can one protect against outside access of the db (i.e. using a db management/sql tool) from someone inserting records with the same id (but different data) into BASE and ENTITY? it seems like this opportunity for error is prevented with the vertical partitioning approach, but not with the horizontal partitioning approach. does jboss compensate somehow for this?
thank you again.
At 18:28 02/12/05 +0100, you wrote:
Hello, > when one entity bean extends another, does the extending entity bean's > table include all of the fields of its parents in its own table? I don't know how this is solved within JBoss, but conceptually you have three possibilities:#1 - typed partitioning the sum of all fields are stored in a base table, having an additional column defining what kind of object it is: base, or extended. for instance BASE String name EXTENDED int age would result in the table BASE having oid INTEGER - object identifier name VARCHAR age INTEGER objType INTEGER (or some kind of IDENTIFIER) #2 - horizontal partitioning all fields are repeated in each table for the subclasses. this would result in a table EXTENDED with oid, name and age, and in a table BASE with oid and name. #3 - vertical partitioning only the very fields belonging to the class are stored in the corresponding table this would result in a table BASE with oid and name, and in a table EXTENDED with oid (also referencing BASE(oid)) and age. > when i deployed 2 entity beans, one extending the other, the extending > bean's db table had all the fields defined of its parents' table... then JBoss adopted the horizontal solution... Regards, Marc
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