One of the main differences will be to do with feautures available to you,
if you take advantage of Oracle functionality then you will either need to
find the alternative in your target system or accept you can’t have it.
Things like compression are likely to be implemented differently, maybe
better, maybe worse. Obviously you no longer have PL/SQL, But there may be
an equivalent.
A fundemental difference will be how transactions work in either system,
you will need to relearn everything. A quick google suggests that InnoDB
has MVCC Non-Blocking Reads which suggests it might not be as much of a
nightmare as others but that’s no excuse to not read up.
The rest of the performance is not going to be down to the cache management
or the details of how it allows you to recover after a crash. It will be
pure and simply the amount of work that your code requires the database to
do. If your code is sensible and effecient then there’s no reason it
shouldn’t also be good enough on a different RDBMS. If your code demands
the DB to do lots of work (chatty slow by slow applications, or ones that
don’t understand filtering etc) then no matter what RDBMS you run it in,
you’re gonna have a bad time.
Ultimately, you are going to rewrite and retest all of your code. It will
take a long time depending on how much time you’ve already invested in your
code in Oracle.
Hope that helps,
Andrew
