Stream Execution of Object Queries

We show a novel execution method of queries over structural data. We present the idea in detail on SBQL (a.k.a. AOQL)—a powerful language with clean semantics. SBQL stands for the Stack-Based Query Language. The stack used in its name and semantics is a heavy and centralised structure which makes parallel and stream processing unfeasible. We propose to process stack-based queries without a stack. The stack-less execution of stack-based queries is done by a network of components connected by streams. Source streams of the network are populated with necessary fragments of objects retrieved from the database. Output streams produce results of the query. This paper focuses on methods of construction, optimisation and effective execution of such a networks. Although this research was inspired by SBQL/AOQL, eventually we achieved a universal execution method for other object-oriented, object-relational and semi-structured language. Especially promising are the optimisation and parallelisation possibilities offered by the presented execution model.