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From Apache Wiki <wikidi...@apache.org>
Subject [Db-derby Wiki] Trivial Update of "OLAPNullOrdering" by BryanPendleton
Date Fri, 20 Jul 2007 00:53:11 GMT
Dear Wiki user,

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

------------------------------------------------------------------------------
  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

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