Hi Mates,
I think psql support var char and odoo has no such variable length fields. 
For a case,
Odoo docs defines: Char: A string of limited length. The required size parameter determines its size.
Where we can give its size as field attribute like size=30 .

But, I am looking for a field (Char / Text) where the size should be dynamic (Based on the value stored in it). I think this can save many reserved memory.
Any hints ?