Fixing duplicate rows to adhere to constraint - postgresql

Question

Is there a way to force existing rows to be unique on a column before adding a unique constraint? I am adding this constraint to my db:
create unique index customfields_name_org_id_key
on CustomFields(name, org_id) where deleted is false;
But would like to first find all cases where this constraint wouldn't be met, and add 1 to the name of one of the rows (adding higher numbers if there are more than 2 colliding rows). So, for example,
SELECT name, org_id, deleted,
row_number() OVER (PARTITION BY name, deleted ORDER BY org_id) AS rnum
FROM customfields ORDER BY org_id;
gives me
name | org_id | deleted | rnum
-----------+--------+---------+------
Another | 1 | f | 1
Bad email | 1 | t | 1
Dog? | 1 | f | 1
New | 1 | f | 1
New | 1 | f | 2
New | 1 | t | 1
New field | 1 | t | 1
and I would like
New | 1 | f | 2
To be renamed "New2"
I have written this code:
update CustomFields
set name = case
when cf.rnum = 1 or cf.deleted
then cf.name
else cf.name || rnum
end
from (SELECT name, org_id, deleted,
row_number() OVER (PARTITION BY name, deleted ORDER BY org_id) AS rnum
FROM customfields ORDER BY org_id) as cf;
But it just takes the first row from the select and renames all the names to "Another". How do I alter this code so that the update works on the corresponding rows in cf?
Sample code: https://www.db-fiddle.com/#&togetherjs=iKSKze0tGm

Answer 1

You could update table by using:
WITH cte AS (
SELECT *,row_number() OVER (PARTITION BY name, deleted ORDER BY org_id) AS rnum
FROM customfields
)
UPDATE CustomFields
SET name = (SELECT case when cf.rnum = 1 or cf.deleted then cf.name
else cf.name || rnum end
FROM cte cf WHERE cf.id = CustomFields.id);
db<>fiddle demo