Translation of SQL queries into a graph structure: Query transformations and pre-optimization issues in a pipeline multiprocessor environment

摘要

We present a model for the transformation of SQL queries into a query tree structure dedicated for execution in a multiprocessor environment supporting pipeline. The translation includes unnesting of nested queries in its first phase, and final transformation into the query tree structure. During the latter phase, without any extra cost, some elementary optimization steps are performed, so that subsequent optimization focuses on more complicated improvements.