> I have a table that contains a varchar and there is a unique constraint
> on that varchar column.
>
> My problem is that I would need the table to allow values that differ
> (only) in trailing whitespace.

...

> Is there any better way to solve this, than using a unique computed
> index on the expression varcharcol || '.' or something similar?

Other possibiliy is to define the column with character set OCTETS.

Or add column containing lenght of field and use both data+length columns
in your constraint.

Ivan