okparanoid@free.fr writes:
> Hello i would like to know if not determining a max size value for a
> character varying's fields decrease the perfomance (perhaps size of
> stockage ?
No, more the other way around: specifying varchar(N) when you had to
pick N out of the air decreases performance, because of all the
essentially useless checks of the string length that Postgres has to
make. If you cannot defend a specific limit N as being required by your
application, then just make it unconstrained varchar (or better text).
Do *not* use char(N) for data with highly variable width; that one
definitely will cost you performance and disk space.
regards, tom lane