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From Apache Wiki <wikidi...@apache.org>
Subject [Ws Wiki] Update of "Tuscany/TuscanyJava/DAS Java Overview/RDBDAS Java User Guide/Partial Update" by KevinWilliams
Date Mon, 02 Oct 2006 18:28:32 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Ws Wiki" for change notification.

The following page has been changed by KevinWilliams:
http://wiki.apache.org/ws/Tuscany/TuscanyJava/DAS_Java_Overview/RDBDAS_Java_User_Guide/Partial_Update

------------------------------------------------------------------------------
  = Partial Update =
  
- The RDB DAS uses the SDO Change Summary to generate a set of database write operations.
 Rather than generated a statment to update all columns in a table that maps to a SDO DataObject
Type, the DAS generates statements that update ony those columns that map to a modified DataObject
property.  For example, consider a Customer DataObject that has had the LastName property
changed.  The '''partial update''' statement generated by the DAS will look somthing like
this:
+ The RDB DAS uses the SDO Change Summary to generate a set of database write operations.
 Rather than generated a statement to update all columns in a table that maps to a SDO DataObject
Type, the DAS generates statements that update ony those columns that map to a modified DataObject
property.  For example, consider a Customer DataObject that has had the LastName property
changed.  The '''partial update''' statement generated by the DAS will look something like
this:
  {{{
     UPDATE CUSTOMER SET LASTNAME = ? WHERE ID = ?
  }}}
@@ -11, +11 @@

     UPDATE CUSTOMER SET FIRSTNAME = ?, SET LASTNAME = ?, SET ADDRESS = ?, SET PHONE = ?,
SET AGE = ?, SET SHOESIZE = ? WHERE ID = ?
  }}}
  
- There are a couple of very good reasons for using a partial update approach.  For one, a
performance boost can be reaized by applications writing to very wide tables.  For example,
this author has seen customer tables with over  100 columns.  I can be a waste of resources
to update 100 columns when only one was modified.  Another reason is that some databases also
employ [http://en.wikipedia.org/wiki/Database_trigger triggers] on specific columns in a table.
 Prtial updates are necessary when column triggers are employed to avoid tripping the trigger
on every row update rather than only on updates to the specific column.
+ There are a couple of very good reasons for using a partial update approach.  For one, a
performance boost can be realized by applications writing to very wide tables.  For example,
this author has seen customer tables with over 100 columns.  I can be a waste of resources
to update 100 columns when only one was modified.  Another reason is that some databases also
employ [http://en.wikipedia.org/wiki/Database_trigger triggers] on specific columns in a table.
 Partial updates are necessary when column triggers are employed to avoid tripping the trigger
on every row update rather than only on updates to the specific column.
  

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