Is it possible to create an index without keeping the indexed data in a column?

Hi,

I would like to create a GIN index on a set of JSON documents. Right now
I'm storing the data in a JSONB column. The current index looks like this:

CREATE INDEX document_payload_idx
ON document
USING gin
(payload jsonb_path_ops);

The index is pretty small, but the actual data takes up a *lot* of space.
Is there a way to get Postgres to index the table *as if* the JSON were
there, but not actually put the data in the table? I could either store the
docs elsewhere and keep a reference, or compress them and put them in the
table in compressed form as a blob.

Thanks much for your help.

Larry