So many broken users due to corrupt database

Product Support
14

Except that that is impossible since the index is broken.
This does the trick:

# create a temporary table without constraints and copy the contents into it
create table users_test (like users);
insert into users_test select * from users;

# remove duplicate usernames case sensitive, the dupes are after Sept 22
delete from users_test where username in (
  select username 
  from users_test 
  group by username 
  having count(username)>1
) and created_at>'2019-09-22' ;

# remove duplicate usernames case insensitive, the dupes are after Sept 22
delete from users_test where lower(username) in (
  select lower(username) 
  from users_test 
  group by lower(username) 
  having count(lower(username))>1
) and created_at > '2019-09-22' ;

# two more problems left, delete them individually
delete from users_test where id in (184534,130826);

# create a new table with constraints and copy the users
create table users_clean (like users including indexes);
insert into users_clean select * from users_test;

and then rename users to users_old and users_clean to users.