Rails - May 2006 - has_and_belongs_to_many with fk constraints?

Hi folks,
I''m wondering if it''s possible to use foreign key constraints
on the join
tables of a has_and_belongs_to_many relation.  Specifically, I get this
error when I try and delete a model I''m using, named saved_search,
which is
many-to-many with neighborhoods.  Any ideas?  Thanks for any help.  :-)

-Eric

Code:
@saved_search.destroy

Error:
Mupdate or delete on "saved_searches" violates foreign key constraint
"neighborhoods_saved_searches_saved_searches_saved_search_id_fk" on
"neighborhoods_saved_searches" DKey (id)=(1) is still referenced from
table
"neighborhoods_saved_searches". Fri_triggers.c L3302
Rri_ReportViolation:
DELETE FROM saved_searches WHERE id = 1


Models
------------
class SavedSearch < ActiveRecord::Base
          has_and_belongs_to_many :neighborhoods
end

class Neighborhoods < ActiveRecord::Base
          has_and_belongs_to_many :saved_searches
end


Join table:
neighborhoods_saved_searches
----------------------------
id         INTEGER     NOT NULL PRIMARY KEY
saved_search_id    INTEGER     NOT NULL        foreign key table:
saved_searches  field: id
neighborhood_id    INTEGER     NOT NULL         foreign key table:
neighborhoods    field: id

The other tables, saved_search, and listings, are normal and have integer id
fields as required.
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