> - Oracle was developed earlier, and one can argue that in those days file systems > were not so great, so there was more need to write your own
Correct me if I'm wrong, but didn't Postgres (or Ingres upon which it's based) development start in the early-to-mid 70's and Oracle's only in the late 70's - early 80's?
" The origins of PostgreSQL date back to 1986 as part of the POSTGRES project at the University of California at Berkeley and has more than 35 years of active development on the core platform." (https://www.postgresql.org/about/)