foreign keys to foreign tables

I'd like to set up a foreign key constraint to a foreign table from a local table.

ie, I have a column in a local table that I'd like to ensure has a value in the foreign table.

alter mytable

add column  some_column_id   uuid references myforeigntable(some_column_id)

;

Unfortunately I get a "not a table" error when I try this.

        ERROR:  referenced relation "myforeigntable" is not a table

I'm thinking I'll have to write a function that checks for existance of the ids in the foreign table, and then put a CHECK constraint on using that function, but I thought I'd as first if there was a better way.

Thanks.

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Rick Otten