1. XML and Databases Exercise Session 10 courtesy of Ghislain Fourny
© Department of Computer Science | ETH Zürich

2. Previously, in XML&Databases
Document
Well-Formedness
(Validation)
Data Model
Processing
XML
with
namespaces
(XML Schema)
optional
XDM
XQuery
<a/>

3. Query Plan

4. java –jar mxquery.jar -f myquery.xquery --explain --discardResult
Query Plan in MXQuery
java –jar mxquery.jar
-f myquery.xquery
--explain
--discardResult

5. Query Plan

6. Query Plan

7. Query Plan

8. Query Plan

9. Query Plan

10. Execution cost
We take the number of processed nodes as a metric.

11. Query Plan
Execution cost 6

12. Query Plan
Execution cost 6 + A( )

13. Query Plan
Execution cost 6 + A( 10 )

14. Query Plan
Execution cost 6 + A( 10 B(7) )

15. Query Plan
Execution cost 6+10A+7AB

16. Redundancies?
Execution cost 6+10A+7AB

17. Redundancies?
Execution cost 6+10A+7AB new: 8+9A+7AB

18. Redundancies?
Execution cost 6+10A+7AB new: 8+9A+7AB better as soon as A>2

19. Query Plan

20. Hope to see you next week!