List the situations for pure Rails where things work in SQLite but not in PostgreSQL

I am creating a website trying to use SQLite for development and test, and PostgreSQL for development (as required by Heroku). Currently I do not need the additional functionality provided by PostgreSQL, but I want to avoid the situation where a bug escapes from all the tests. I will not directly write any SQL query, but only Rails codes (so things like this and this will not be a problem). Current known examples are:

• Column types matter. where :string_column => <integer> will work fine in SQLite and break in Postrges. (Thanks to spike!)
• Grouping issues, as described in 1 and 2 (I don't quite understand this, but it seems possible to cause problem even with pure Ruby).

Any more?