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From Apache Wiki <wikidi...@apache.org>
Subject [Db-derby Wiki] Update of "OLAPRowNumber" by ThomasNielsen
Date Tue, 05 Feb 2008 12:13:01 GMT
Dear Wiki user,

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

The comment on the change is:
typo in header

------------------------------------------------------------------------------
  
  Yet another PRN is used to top off the upper WindowNode. This PRN is effectively a no-op,
and is eliminated during code generation. The PRN is mainly there due to other parts of the
code expecting the top node to be a PRN once we are done with the access path modification.
  
- === Code generation === 
+ === Code generation ===
  
  During code generation, we lay out code to generate a WindowResultSet, and pass the source
resultset information as well as column info to it. The logic for ROW_NUMBER() over the empty
window specification is simply a counter in the WindowResultSet, so this change should be
seen as part of the window function framework. The intended use of this result set is mainly
other window functions that may need row caching to calculate moving averages over a window
or other features and functionallity needed for the window function being implemented.
  

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