Physical Mappings of XQuery
The previous sections have presented the functional description of how to integrate XQuery and XML into the SQL processing model of relational systems. From a performance point of view, another interesting aspect is how such combined queries are being mapped into a physical operator tree. Since this mapping depends on the physical mapping of the XML datatype and also depends heavily on the vendor-specific architectures, this section provides a more general, higher-level discussion of the different mapping strategies of XQuery into physical execution plans.
In the following, we assume that the XQuery expressions are provided as constants; thus, compilation can occur at the same time as the compilation of the SQL expressions. ...
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