Xpath to XQuery

Double Pipelined Join (Tukwila)

Hash Join

8Partially pipelined: no output until inner read

8Asymmetric (inner vs. outer) — optimization requires source behavior knowledge

Double Pipelined Hash Join

4Outputs data immediately

4Symmetric — requires less source knowledge to optimize


	DPJoin picture
	Cite Wilschut 91 PDIS
	Mention that we use multithreading to achieve same effect