Caching with ’good enough’ currency, consistency, and completeness

SQL extensions that allow queries to explicitly specify data quality requirements in terms of currency and consistency were proposed in an earlier paper. This paper develops a data quality-aware, finer grained cache model and studies cache design in terms of four fundamental properties: presence, consistency, completeness and currency. The model provides an abstract view of the cache to the query processing layer, and opens the door for adaptive cache management. We describe an implementation approach that builds on the MTCache framework for partially materialized views. The optimizer checks most consistency constraints and generates a dynamic plan that includes currency checks and inexpensive checks for dynamic consistency constraints that cannot be validated during optimization. Our solution not only supports transparent caching but also provides fine grained data currency and consistency guarantees. 1