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The following page has been changed by Shravan Narayanamurthy:
http://wiki.apache.org/pig/PigExecutionModel

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   1. The mapping from logical operators to physical operators aims at 
preserving isomorphism of computation trees. Hence, most logical operators have 
their counterpart in physical operators. For instance, a logical FILTER will be 
translated into a physical FILTER. See translation scheme below.
   1. These are the following exceptions:
      1. Logical Cogroup to be translated into a Physical LocalRearrange and 
GlobalRearrange.
- 
+     2. Chris mentioned that even Algebraic Functions are exceptions to this.
  
  === Logical to Physical Translation Scheme ===
  
@@ -161, +161 @@

  
  attachment:FILTERTranslation.png
  
+ === Comments ===
+ 
+ The Physical plan and the Logical Plan were not clear to me probably because 
of the nested query plan thingy. I think we need to find a better way to draw 
this because, the conditional expression is an attribute of the filter and not 
an input to filter.
+ 

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