"Seeing their blogs mysql-> postgres followed by a postgres -> mysql migration" this is not clear to you? Perhaps a visit to an optician is in your best interest.

And why do you make the assumption, i'm a postgresql expert to answer that question.

Though others did, so if you would have bothered to read the other thousands of comments on the matter. You would not have needed to ask this question,

PostgreSQL Heap-Only-Tuples (HOT) from: http://use-the-index-luke.com/blog/2016-07-29/on-ubers-choic...