Forum OpenACS Q&A: Response to Bizarre Postgres Behavior

There is an "on delete cascade" for the foreign key you are referring to, meaning that when the key is deleted from sec_sessions, the corresponding rows are also deleted from sec_session_properties (silently; AFAIK there is no indication that another table has been effected in what postgres returns).  If you try to delete a row is referenced by a FK w/o the cascade, you will get an error.