O-O, What Have They Done to DB2?

In this paper, we describe our recent experiences in adding a number of object-relational extensions to the DB2 Universal Database (UDB) system as part of a research and development project at the IBM Almaden Research Center. In particular, we have enhanced DB2 UDB with support for structured types and tables of these types, type and table hierarchies, references, path expressions, and object views. In doing so, we have taken care to design and implement the extensions in such a way as to retain DB2's ability to fully optimize queries and (in our next step) to support business rules and procedures through the provision of constraints and triggers. We describe each of the SQL language extensions that we have made, discuss the key performance tradeoffs related to the design and implementation of these features, and explain the approach that we ended up choosing (and why). Most of the features described here are currently shipping as part of Version 5.2 of the DB2 UDB product. We end this paper with a summary of the current status of our work and a discussion of what we plan to tackle next.