[Solr Wiki] Update of "FunctionQuery" by umar

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The following page has been changed by umar:
http://wiki.apache.org/solr/FunctionQuery

The comment on the change is:
added an example for usage of function query

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  max(x,c) returns the max of another function and a constant.  Useful for "bottoming out" another function at some constant.
      Example Syntax: '''max(myfield,0)'''
  
+ === General Example ===
+     To give more idea about teh use of the function query, suppose index stores dimensionsin metres '''x''', '''y''','''z''' of different some hypothetical boxes with arbitary names stored in field '''boxname'''.
+     suppose we want to search for box matching name ''findbox'' but ranked according to volumes of boxes, the query params would be: '''q=boxname:findbox _val_:"product(product(x,y),z)"'''.
+     Although this will rank the results based on volumes but in order to get the computed volume you will need to add parameter '''&fl=*, score'''   where '''score''' will contain the resultant volume.
+     Suppose you also have a field containing weight of the box as 'weight', then to sort by the density of the box and return the value of the density in score you query should be:
+ 
+ 
+     '''http ://localhost:8983/solr/select/?q=boxname:findbox _val_:"div(weight,product(product(x,y),z))"&fl=boxname x y z weight score'''
+     
+