First published on the Tech Style blog .

When a company moves off Oracle, most of the effort goes into converting the code. The part that hurts later is quieter. PostgreSQL is not Oracle, and in places it computes a different answer to the same expression. There is no error at build time and none in test. A pricing query returns a slightly wrong number, and a customer is the one who finds it.

Paritas is our answer to that. It is PostgreSQL 18 with an Oracle mode that compiles and runs real PL/SQL: packages, triggers, collections and exceptions. It is still in development and not for sale. This post is mostly about how we test it, because that is the part we think matters.

Same code, different answers

Here are three cases, each measured on live engines with Oracle Database 21c as the reference. All three convert cleanly. None raises an error you would see at build time.

SELECT 3.4e38f * 10f multiplies binary floats past the top of the type. Oracle returns inf .…