Text search without dictionary ?

Hello,

I have some columns containig list of codes (e.g. 'Af45De Uz76 I98ht ...
')
and I'd like to build full text search indexes on them.

As these strings are basically a list of IDs , I don't need any
dictionary.
I've built an own simplified parser whose output is sufficient.

My concern is about the lowercase transformation of the simple
dictionary
which anyway don't reduce the number of lexemes significantly.

I could easily workaround this while rechecking the strings,
but I wonder if there is a simple way to disable the lowercse
transformation as I don't need it...

Maybe someone can also point me to some documentation about writing my
own dummy dictionnary?

(I'm currently experimenting with 8.3.6, but we will probably implement
such functionalities only with 8.4)

Thanks,

Marc Mamin