Incremental Recomputation of Recursive Queries with Nested Sets and Aggregate Functions

We examine the power of incremental evaluation systems that use an SQL-like language for maintaining recursively-de ned views. We show that recursive queries such as transitive closure, and \alternating paths" can be incrementally maintained in a nested relational language, when some auxiliary relations are allowed. In the presence of aggregate functions, even more queries can be maintained, for example, the \same generation" query. In contrast, it is still an open problem whether such queries are maintainable in relational calculus. We then restrict the language so that no nested relations are involved (but we keep the aggregate functions). Such a language captures the capability of most practical relational database systems. We prove that this restriction does not reduce the incremental computational power; that is, any query that can be maintained in a nested language with aggregates, is still maintainable using only at relations. We also show that one does not need auxili...

• Type: Conference
• Year: 1997
• Where: DBPL
• Authors: Leonid Libkin, Limsoon Wong
• Keywords: Database, DBPL 1997, Nested Relational Language, Practical Relational Database, Relational Database Systems