7.5. Indexing XML Data

xml data type instances are stored as binary large objects (BLOB ) in xml data type columns. If these columns are not indexed, they must be shredded at runtime for each row in the table to evaluate a query. This can be costly, especially with large xml data type instances or a large number of rows in the table. Building primary and secondary XML indexes on xml data type columns can significantly improve query performance.

Shredding is the process of mapping and converting an XML document into tables in a relational database.