Updatable view should truncate table fields

Using PostgreSQL 9.0.

We have a table which is not accessible by client code.
We also have views with rules and triggers to intercept any insert or update statements and write that data in a slightly different format back to the table.

A particular field in the table is currently 5 chars but recently we have had update / insert statements containing more than 5.
This obviously (and correctly) throws an error.

We can extend the table to accept more than 5 characters but the view must return 5 characters.
If we try to extend the table to accept, say, 10 characters the view will display 10.
If I also cast the view field to 5 characters then any insert with more than 5 characters still fails.

Any ideas???

Create table blah_table
(
blah_id int,
fixed_field char(5)
);

Create or replace view blah_view as
Select
blah_id,
fixed_field
from blah_table;

CREATE OR REPLACE FUNCTION process_blah_insert(blah_view) RETURNS void AS $body$
Begin

Insert into blah_table
(
blah_id,
fixed_field
)
Select
$1.blah_id,
$1.fixed_field
;
End;
$body$ language plpgsql;

CREATE OR REPLACE FUNCTION process_blah_update(blah_view) RETURNS void AS $body$
Begin

Update blah_table
Set
fixed_field = $1.fixed_field
where
blah_id = $1.blah_id
;
End;
$body$ language plpgsql;

create or replace rule blah__rule_ins as on insert to blah_view
do instead
SELECT process_blah_insert(NEW);

create or replace rule blah__rule_upd as on update to blah_view
do instead
SELECT
process_blah_update(NEW);

insert into blah_view values (1, '12345');
insert into blah_view values (2, '123456'); --This line fails obviously

Regards,

Russell Keane

INPS

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