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Specifying SQL Generation Algorithms

The algorithms DataDirect XQuery® uses to create hierarchies are optimal for creating large, complex documents, but still good for smaller documents with shallower hierarchies. If query results contain four or fewer levels of hierarchy, and your performance seems inadequate, you will sometimes get better performance if you tell DataDirect XQuery® to use either outer join or sorted outer union (see the DataDirect 2.0 User's Guide and Reference for details on these algorithms). There are several ways to specify SQL generation algorithms in DataDirect XQuery®:

    XQDataSource ds = new DDXQDataSource(); 
    ds.setJdbcPragmas("sql-rewrite-algorithm=nested-loop");          
            

    <pragma name="sql-rewrite-algorithm">outer-join</pragma>      
            

    declare option ddtek:sql-rewrite-algorithm "outer-join";