Casey Allen Shobe <[EMAIL PROTECTED]> writes:
> create table  "schemes" (
> ...
>       "user_id"       integer         not null references "pg_user" ("usesysid"),
> ...
> ERROR:  Referenced relation "pg_user" is not a table

> As you can hopefully see, I need to reference the postgres user table
> for data integrity.  Can this be done?

Nope :-(.  The immediate cause of that complaint is that pg_user isn't
a table; it's only a view on pg_shadow.  But even if you'd referenced
pg_shadow, the command would have been rejected.  The difficulty is that
foreign-key constraints require triggers, and we don't support
user-defined triggers on system catalogs.  (That would imply the ability
to run arbitrary user-defined code during system catalog updates, which
has a ton of problems that I won't enumerate here.)

                        regards, tom lane

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