"UPDATE table_name SET w = $1, x = $2, z = $4 WHERE y = $3 RETURNING *",
does not do the same as
"UPDATE table_name SET w = $1, x = $2, y = $3, z = $4 RETURNING *",
It’s 2 am and my mind blanked out the WHERE, and just wanted the numbers neatly in order of 1234.
idiot.
FML.
This is a hard lesson to learn. From now on, my guess is you will have dozens of backups.