Enhancing the Tree Awareness of a Relational DBMS: Adding Staircase Join to PostgreSQL
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چکیده
Given a suitable encoding, any relational DBMS is able to answer queries on tree-structured data. However, conventional relational databases are generally not (made) aware of the underlying tree structure and thus fail to make full use of the encoded information. The staircase join is a new join algorithm intended to enhance the tree awareness of a relational DBMS. It was developed to speed up the SQL-based evaluation of XPath expressions. The algorithm encapsulates tree-specific knowledge and relies on the data provided by the XPath accelerator, an encoding which maps information about the tree-shaped structure of an XML document to a relational database table. This thesis shows that it is possible to incorporate the staircase join into a conventional RDBMS, namely the open-source RDBMS PostgreSQL. The implementation involved local changes to three out of four query processing stages in the PostgreSQL backend: the parser, the planner/optimizer, and the executor. The performance tests subsequently carried out in the tree-aware PostgreSQL instance confirmed that the staircase join leads to a substantial query speed-up. In comparison to the native join algorithm which is chosen by the original PostgreSQL database to evaluate SQL-based XPath expressions, the staircase join produced an improvement up to several orders of magnitude. Thus, the tests have shown that, in conjunction with a suitable cost model, the staircase join can turn a relational database system into an efficient XML query processing solution.
منابع مشابه
An Injection with Tree Awareness Adding Staircase Join to PostgreSQL
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تاریخ انتشار 2004