Efficient support of XQuery Full Text in SQL/XML enabled RDBMS

There has been more than decade of efforts of supporting storage, query and update XML documents in RDBMS. XML enabled RDBMS supports SQL/XML standard that defines XMLType as a SQL data type and allows XQuery/XPath embedded in XMLQuery(), XMLExists() and XMLTABLE() in SQL. In XML enabled RDBMS, both relational data and XML documents can be managed in one system and queried using SQL/XML language. However, the use case of management of document centric XML is not well-addressed due to the lacking of full text query constructs in XQuery. Recently, XQuery Full Text (XQFT) becomes the W3C recommendation. In this paper, we show how XQFT can be supported efficiently in SQL/XML for full text search of XML documents managed by XML enabled RDBMS, such as Oracle XMLDB. We present architecture of a new XML Full Text Index, XQuery compile time and run time enhancements to efficiently support XQFT in SQL/XML. We present our design rationale on how to exploit Information Retrieval (IR) techniques for XQFT support in RDBMS. The new XML Full Text Index can index common XML physical storage forms: such as text XML, binary XML, relational decomposition of the XML. Although our work is built within Oracle XMLDB, all of the presented principles and techniques in this paper are valuable enough to RDBMS industry that needs to effectively and efficiently support of XQFT over persisted XML documents.