When using tsearch one usually, often, creates a tsvector column to put data in, and then create index on it.
But, do you really need the index? I wrote once already that you don't have to, but then a person talked with me on IRC, and pointed this section of docs:
One advantage of the separate-column approach over an expression index … Another advantage is that searches will be faster, since it will not be necessary to redo the to_tsvector calls to verify index matches.
So, let's see how big of a problem it really is.