Exploring performance issues for a clinical database organized using an entity-attribute-value representation

Background: The entity-attribute-value representation with classes and rela tionships (EAV/CR) provides a flexible and simple database schema to store heterogeneous biomedical data. In certain circumstances, however, the EAV/C R model is known to retrieve data less efficiently than conventionally base d database schemas. Objective: To perform a pilot study that systematically quantifies performance differences for database queries directed at real-w orld microbiology data modeled with EAV/CR and conventional representations , and to explore the relative merits of different EAV/CR query implementati on strategies. Methods: Clinical microbiology data obtained over a ten-year period were stored using both database models. Query execution times were compared for four clinically oriented attribute-centered and entity-centere d queries operating under varying conditions of database size and system me mory. The performance characteristics of three different EAV/CR query strat egies were also examined. Results: Performance was similar for entity-cente red queries in the two database models. Performance in the EAV/CR model was approximately three to five times less efficient than its conventional cou nterpart for attribute-centered queries. The differences in query efficienc y became slightly greater as database size increased, although they were re duced with the addition of system memory. The authors found that EAV/CR que ries formulated using multiple, simple SQL statements executed in batch wer e more efficient than single, large SQL statements. Conclusion: This paper describes a pilot project to explore issues in and compare query performanc e for EAV/CR and conventional database representations. Although attribute- centered queries were less efficient in the EAV/CR model, these inefficienc ies may be addressable, at least in part, by the use of more powerful hardw are or more memory, or both.