@Override
    public <U> PostgreSQLQuery<U> select(Expression<U> expr) {
        queryMixin.setProjection(expr);
        @SuppressWarnings("unchecked") // This is the new type
                PostgreSQLQuery<U> newType = (PostgreSQLQuery<U>) this;
        return newType;
    }
{@code PostgreSQLQuery} provides Postgres related extensions to SQLQuery.

If you need to subtype this, use the base class instead.

@param <T> the result type
querydsl-sql/src/main/java/com/querydsl/sql/postgresql/PostgreSQLQuery.java