If it's not an indexed column (and your page isn't too full), it can do a HOT update, which is effectively the same as an in-place write if you're flushing to d

If it's not an indexed column (and your page isn't too full), it can do a HOT update, which is effectively the same as an in-place write if you're flushing to disk at page granularity anyway unless you have really wide rows.