A Strategy for Partial Evaluation of Views
Parke Godfrey, Jarek Gryz · Intelligent Information Systems · 2000
Database applications and environments such as mediation over heterogeneous database sources and data warehousing for decision support lead to complex queries. Queries are often nested, defined over views, and may involve unions. In certain cases, one might want to “remove” pieces ( sub-queries or sub-views ) from such queries. Some sub-views may be effectively cached, or may be materialized views. Some may be known to evaluate empty, through reasoning over the integrity constraints. Some may match protected queries, which for security cannot be evaluated. We introduce an evaluation strategy called tuple-tagging for queries defined over views that efficiently “removes” marked sub-views. This differs from the approach of rewriting the query so that the sub-views to be removed are effectively gone, and then evaluating the rewritten query. With the tuple tagging evaluation, no rewrite of the original query is necessary. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.