[Db-derby Wiki] Trivial Update of "OLAPNullOrdering" by BryanPendleton

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The following page has been changed by BryanPendleton:
http://wiki.apache.org/db-derby/OLAPNullOrdering

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  There are several parts to implementing the <null ordering> feature for Derby:
  
   * The new syntax must be added to the SQL grammar
-  * The null ordering specification must be passed around through the compiler data structures so that it eventually gets passed to the sorter
+  * The null ordering specification must be passed around through the compiler data structures so that it eventually gets passed to the sorter. This involves data structures like {{{OrderByList}}} and {{{OrderByColumn}}}. Eventually, the compiler must set up the correct {{{ColumnOrdering}}} objects, which I think happens in {{{RowOrderingImpl.addOrderedColumn}}}
   * The sorter must be changed so that in addition to having a columnOrderingMap and a columnOrderingAscendingMap, it also has a columnOrderingNullOrderingMap, where it records the NULLS FIRST or NULLS LAST specification for each column in the sort.
   * The sorter must pass the user's choice to the DataValueDescriptor.compare() method call.
   * The DataValueDescriptor.compare(DataValueDescriptor other) method must be changed to allow the null ordering choice to be passed in