Hi, I have a table with over 500K rows, and I want to update some
"timestamp without time zone" fields.
UPDATE order_update SET last_attempt_ts = (last_attempt_ts AT TIME ZONE 'EST') AT TIME ZONE 'UTC';
Well, you are updating all rows in the table, not just "some". This is going to take a while and as you are touching all rows in the table (because no WHERE clause is specified) there is not a good way to speed this up.