Andreas Kalsch <andreaskalsch(at)gmx(dot)de> writes:
> But with this operation you will recreate the whole index. - I have
> found out, that the name of the constraint's index is the same as the
> constraint, so that I can simply rename the index.
You'd probably better rename the constraint too to avoid confusion.
Failing anything else, there's always direct UPDATE of the pg_constraint
catalog.
regards, tom lane