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Building Streams
Figure 5-19
Setting stream optimization options
Note: W
hether SQL pushback and optimiz ation are suppo r ted depends on the type of databa se in
use. For the latest information on which databases and O DBC drivers are supported and tested f or
use with IBM® SPSS® Modeler 15, see the corporate Suppo r t site at http://www.ibm.com/support.
Enable stream rewriting.
Select this option to enable stream rewriting in SPSS Modeler. Two types
of rewriting are available, and you can select one or both. Stream rewriting reorde r s the nodes in a
stream behind the scenes for more efficient operation, withou t altering s tream semantics.
Optimize SQL generation.
This option enables nodes to be reordered within the stream so that
more operations can be pushed back using SQL generation for execution in the database.
When it finds a node that cannot be rendered into SQL, the optimizer will look ahead to
see if there are any downstream nodes that can be re ndered into SQL and safely moved in
fron
t of the problem node without affecting the stream semantics. Not only can the database
perform operations more efficiently than SPSS Modeler, but such pushbacks act to reduce
the size of the data set that is returned to SPSS Modeler for processing. Thi s, in turn, can