Some of the many mistakes I have made are that of being " lazy" and instead of creating some tables and some schema structure and all the related code I just serialized the stuff and stored it as a string in the database. A few month later or less a very simple be requirement arise and I have to filter by a thing inside the serialization string. Then I say ok, let's index separately the thing, or store it independently, or do two pass filtering, but none of these beats the very simple query I could have done if I had done the right thing in the first place. I hid the complexity away but it came back to me weeks later and then it really stunk: the choice is between many evils, migrate existing data, duplicate the thing, select by regexp, etc.
