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The following page has been changed by AlanGates:

+ == Semantics ==
+ The comparator provided by the user will be applied to the whole ORDER BY 
key.  This was chosen for two reasons:
+  1. Providing a separate comparator for every element in the key would make 
the syntax burdensome.
+  2. It is not planned that this mechanism be used to provide comparators for 
user defined types.  Those should be provided as part of the type instead.  
This lessens the need for per key comparators.
  == Logical and Physical Plan Changes ==
  When an ORDER BY clause is encountered in a query a `ProjectSpec` is created
  and passed to the `SortDistinctSpec` that controls how a sort is done.
@@ -84, +89 @@

  returning the default comparator or a user provided one rather than always
  taking the result of this and setting `userComparator`.
+ == Future Considerations ==
+ In the future, it is proposed that ORDER BY will allow ascending and 
descending order per key, in a SQL like manner (see ProposedRoadMap).  This 
will not work well with the fact that this user provided comparator works on 
the entire key.  If ascending/descending is added in the future, the parser 
should also be modified to make it an error to use these key words with a user 
provided comparator.

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