61
Building Streams
Figure 5-19
Settingstre am optimization options
Note: Whether SQL pushback and optimization are supported depends on the type of database in
use. For the latest information on which databases and ODBC drivers are supported and tested f or
usew ith IBM® SPSS® Modeler 15, see the corporate Support site at http://www.ibm.com/support.
Enablestream rewriting. Select this option to enable stream rewriting in SPSS Modeler. Twotypes
of rewriting are available, and you can select one or both. Stre am rewriting reorders the nodes in a
stream behind the scenes for more efficient operation, without altering stream semantics.
OptimizeSQL ge neration. This option enables no des 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 rendered into SQL and safely moved in
front of the problem node without affecting the stream semantics. Notonly ca n 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. This, in turn, can