I have a hard time believing PostgreSQL performance is better than Oracle, can you give an example? How big is your database and how much did migrating cost you?
A lot of people who think Oracle is amazingly fast, think so because who puts a million dollar DB on thousand dollar hardware? Put any major DB on equivalent hardware and you'll get some pretty damn good performance.
My experience is that Postgres has better performance than Oracle on much smaller machines. If you have very simple data, with very simple joins, and never deviate from the trivial "select columns from table join table using (foreign key)" you may have a different experience, because Oracle is just great on those.
https://www.informationweek.com/open-source-postgresql-trail...