There is also the option of pg_stat_statements: https://www.postgresql.org/docs/current/static/pgstatstatements.html and auto_explain: https://www.postgresql.org/docs/current/static/auto-explain.html
These should help you identify what is slowing things down. There is no reason I could think of you should be seeing a 10x slowdown between Postgres and Oracle, so you'll likely have to just profile it to find out.
