Database Change Notifications: Primitives for Efficient Database Query Result Caching

Many database applications implement caching of data from a back-end database server to avoid repeated round trips to the back-end and to improve response times for end-user requests. For example, consider a web application that caches dynamic web content in the mid-tier [3, 2]. The content of dynamic web pages is usually assembled from data stored in the underlying database system and subject to modification whenever the data sources are modified. The workload is ideal for caching query results: most queries are read-only (browsing sessions) and only a small portion of the queries are actually modifying data. Caching at the mid-tier helps off-load the back-end database servers and can increase scalability of a distributed system drastically.