I don't know how hard it would be to do, but I have rewritten some
Oracle code to work on PostgreSQL. While rewriting a couple functions,
and the tedium of changing SYSDATE to CURRDATE were a pain, these things
can be handled with a scripting language. The big problem, which means
that PostgreSQL code does not go back to Oracle, is the "join" syntax.
If there was a way to adopt the Oracle join syntax in addition to the
standard join syntax. It would make a great deal of difference. The
tedium of formatting and variable naming can be done by almost anyone.
The rewriting of complex queries into a completely different logical
syntax, can only be done by a knowledgeable person and a good QA team.