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From Apache Wiki <wikidi...@apache.org>
Subject [Ws Wiki] Update of "WorkingWithPaging" by KevinWilliams
Date Mon, 30 Oct 2006 18:58:27 GMT
Dear Wiki user,

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The following page has been changed by KevinWilliams:
http://wiki.apache.org/ws/WorkingWithPaging

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- The RDB DAS provides a mechanim for working with the result of large queries one chunk (page)
at a time.  This capability is modeled after the behavior of web search engines.  For example,
if I Google "RDB DAS" I am presented with a page representing the first ten references.  I
am also told that there were close to 500,000 mathces and I am given the opportunity to go
to the next page or directly to pages two through ten.  After movng from the first page I
am also provided the opportunity to move back to some previous page.
+ The RDB DAS provides a mechanism for working with the result of large queries one chunk
(page) at a time.  This capability is modeled after the behavior of web search engines.  For
example, if I Google "RDB DAS" I am presented with a page representing the first ten references.
 I am also told that there were close to 500,000 matches and I am given the opportunity to
go to the next page or directly to pages two through ten.  After moving from the first page
I am also provided the opportunity to move back to some previous page.
  
  The DAS "Pager" is a wrapper around a provided read command and provides the APIs for paging.
 Here is the Pager interface:
  {{{
@@ -25, +25 @@

  }
  }}}
  
- A Pager is instantiated on a given read Command and the constructor is used to specify the
desired page size (number of dataase rows per page).  The following example illustrates constrution
and use of a pager:
+ A Pager is instantiated on a given read Command and the constructor is used to specify the
desired page size (number of database rows per page).  The following example illustrates construction
and use of a pager:
  {{{
     DAS das = DAS.FACTORY.createDAS(getConnection());
     // Build command to read all customers
@@ -50, +50 @@

     customer2 = root.getDataObject("CUSTOMER[2]");
  }}}
  
+ 
+ The current Pager specification and implementation are very preliminary and will likely
change in significant ways! For instance, the pager is intended to work in completely disconnected
scenarios so there should be no connection context maintained between invocations of the pager.
 Currently the Pager references a Command that, in turn, references a connection (oops!).
 Some work must be done to make the pager lightweight as it will likely be stored in session.
+ 
+ We probably should also create a Factory rather than using the impl constructor.
+ 

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