Hi All
I have a usecase where I may need to modify the primary key value of
a table.
For achieving this I create a unit of work, read the entity (E) from
the database, register E with UOW and delete E from the UOW. I then
create a new entity E1. I populate all the required direct to field
mappings and register E1 with UOW. When I commit the UOW, the new
row appears on the database with the modified primary key column
value.
This works fine for the single table scenario.
But assume that E spans across tables T1 and T2. T1 has a one-to-one
mapping to table T2. Also delete is set to cascade from T1 to T2. So
when I delete an entity constructed from T1, indeed the
corresponding row in T2 is deleted.
However in the above scenario since I am working with the same unit
of work I am observing some weird behavior. When I delete E from
UOW, I expect that the corresponding rows in T2 should automatically
be considered as deleted. So when I create E1, I try to insert the
corresponding rows (entities) of T2 again and link them to E1. But
before I do this insert for T2 entities I do a check on whether the
entity already exists in T2 or not. As it turns out, I am able to
read the T2 entity before the insert (I am doing the read using the
same UOW). This violates the invariant that I established earlier -
corresponding entities of T2 should be deleted when E is deleted
from UOW.
Am I missing something about object identities? Is this expected
behavior?
For my usecase, the primary key columns that have to be modified are
from T1 only. So I think I will be better off creating a
DeleteObjectQuery that deletes the record from T1 alone and
reinserts it into T1 with the modified primary key value. The delete
would not cascade to T2 in such a scenario (I think this should be
possible with a DeleteObjectQuery). This would of course require
delayed processing of foreign key constraints on the database. Can
someone please suggest whether this should be the way to go?
--
Thanks and Regards
Rohit Banga
Member Technical Staff
Oracle Server Technologies
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