ISAM Emulation: The PGDBE is capable of emulating 100% of xBase ISAM (Indexed Sequential Access Method) functions and commands. This is achieved through advanced partitioned caching concepts and intelligent dynamic query generation. Emulating the ISAM system within a PostgreSQL environment is a major technical achievement, given the differences between these systems.
ISAM Record Locking: PGDBE supports ISAM record locking semantics, using an Inter-Process Communication (IPC) mechanism instead of file-locking. This ensures fair lock distribution and is a more robust and sophisticated method of managing concurrent access to data records, providing a significant advantage in multi-user environments.
ISAM Indexes: Within the context of ISAM indexes, PGDBE supports all Xbase++ expressions, regardless of their complexity, and includes support for user-defined functions. This is a significant capability that allows for highly complex data manipulation and retrieval operations within the ISAM framework.
Efficiency: Despite the complexity of emulating ISAM, the PGDBE manages to outperform traditional DBF/NTX/CDX storage engines in multi-user scenarios. This efficiency is a testament to the robustness and optimization of the underlying algorithms and design principles of the PGDBE.
Pass-through-SQL Support: PGDBE's capability to support pass-through-SQL in addition to ISAM emulation, all against the same data source, is a noteworthy feature. While pass-through-SQL itself is not particularly impressive, the ability to use both ISAM and SQL operations interchangeably adds a significant level of flexibility and power to the database engine.