Full Text Index Scanning

I'm in the process of migrating a project from Oracle to Postgres and have
run into a feature question. I know that Postgres has a full-text search
feature, but it does not allow scanning the index (as opposed to the data).
Specifically, in Oracle you can do "select * from table where
contains(colname,'%part_of_word%')>1". While this isn't terribly efficient,
it's much faster than full-scanning the raw data and is relatively quick.

It doesn't seem that Postgres works this way. Attempting to do this returns
no rows: "select * from table where to_tsvector(colname) @@
to_tsquery('%part_of_word%')"

The reason I want to do this is that the partial word search does not
involve dictionary words (it's scanning names).

Is this something Postgres can do? Or is there a different way to do scan
the index?

TIA,

Matt