Interesting problem, Why did this happen with an index?

One of the developers here just came accross an interesting problem, I am
interested to know if there is anyone out there that can explain this to me
as to why the sql server internals are behaving this way:
Table A - > has a trigger for delete that does this: Delete FROM table B.
Table B - > has an FK to table A with On Cascade delete defined.
As is, DELETE FORM TableA works perfect, no problems.
Now, for performance reasons, a unique index is introduced on Table B that
includes the FK.
Now, DELETE FORM TableA causes an error indicating that the nesting of
triggers, stored procedures, etc, is greater than 32.
If anyone can explain why the introduction of an index in this case results
in the nesting limit being exceeded, it clearly created a never ending loop
some how, I am just unclear as to how this is happening.
Thanks,
Rick.Rick wrote:
> One of the developers here just came accross an interesting problem,
> I am interested to know if there is anyone out there that can explain
> this to me as to why the sql server internals are behaving this way:
> Table A - > has a trigger for delete that does this: Delete FROM
> table B.
> Table B - > has an FK to table A with On Cascade delete defined.
> As is, DELETE FORM TableA works perfect, no problems.
> Now, for performance reasons, a unique index is introduced on Table B
> that includes the FK.
> Now, DELETE FORM TableA causes an error indicating that the nesting of
> triggers, stored procedures, etc, is greater than 32.
> If anyone can explain why the introduction of an index in this case
> results in the nesting limit being exceeded, it clearly created a
> never ending loop some how, I am just unclear as to how this is
> happening.
> Thanks,
> Rick.
Is this a real production issue? If so, why do have a trigger on table A
to delete related rows from table B and a cascade FK on Table B to
delete related rows in Table A. Design-wise, it seems messy and
unmanageable. Or is this just a case of a developer trying to break SQL
Server.
Can you provide more details. What rows are being deleted from the
trigger? What is the actual relationship between the tables?
--
David Gugick
Imceda Software
www.imceda.com