GNU SQL Server
GNU SQL Server is a free portable multi-user relational database management system. It supports the full SQL89 dialect and has some extensions from SQL92. GNU SQL Server implements highly isolated transactions, and static & dynamic query compilation. Both, client & server sides of the system work on Unix-like systems. Client/server interaction is based on an RPC mechanism. The server sub processes facility requires message passing and memory sharing facilities. The most interesting results of the research are as follows:
- cost-based query optimization with non-uniformed column values distribution;
- predicate-based locking schema for transaction coordination;
- separate logical and physical logging and recovery.
More information on the system and downloads can be found at GNU SQL Server home page.