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From Apache Wiki <wikidi...@apache.org>
Subject [Solr Wiki] Update of "FunctionQuery" by GrantIngersoll
Date Sat, 14 Nov 2009 14:09:34 GMT
Dear Wiki user,

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

The "FunctionQuery" page has been changed by GrantIngersoll.
http://wiki.apache.org/solr/FunctionQuery?action=diff&rev1=30&rev2=31

--------------------------------------------------

  == constant ==
  <!> [[Solr1.3]] Floating point constants.
  
+  . Example Syntax: '''1.5''' SolrQuerySyntax Example: '''_val_:1.5'''
-  . Example Syntax: '''1.5'''
-  SolrQuerySyntax Example: '''_val_:1.5'''
  
  == fieldvalue ==
  This function returns the numeric field value of an indexed field with a maximum of one
value per document (not multiValued).  The syntax is simply the field name by itself.  0 is
returned for documents without a value in the field.
  
+  . Example Syntax: '''myFloatField''' SolrQuerySyntax Example: '''_val_:myFloatField'''
-  . Example Syntax: '''myFloatField'''
-  SolrQuerySyntax Example: '''_val_:myFloatField'''
  
  == ord ==
  ord(myfield) returns the ordinal of the indexed field value within the indexed list of terms
for that field in lucene index order (lexicographically ordered by unicode value), starting
at 1. In other words, for a given field, all values are ordered lexicographically; this function
then returns the offset of a particular value in that ordering. The field must have a maximum
of one value per document (not multiValued).  0 is returned for documents without a value
in the field.
  
   . Example: If there were only three values for a particular field: "apple","banana","pear",
then ord("apple")=1, ord("banana")=2, ord("pear")=3
+  Example Syntax: '''ord(myIndexedField)''' Example SolrQuerySyntax: '''_val_:"ord(myIndexedField)"'''
-  Example Syntax: '''ord(myIndexedField)'''
-  Example SolrQuerySyntax: '''_val_:"ord(myIndexedField)"'''
  
  WARNING: as of Solr 1.4, ord() and rord() can cause excess memory use since they must use
a FieldCache entry at the top level reader, while sorting and function queries now use entries
at the segment level.  Hence sorting or using a different function query, in addition to ord()/rord()
will double memory use.
  
@@ -47, +44 @@

  == rord ==
  The reverse ordering of what ord provides.
  
-  . Example Syntax: '''rord(myIndexedField)'''
-  Example: '''rord(myDateField)''' is a metric for how old a document is: the youngest document
will return 1, the oldest document will return the total number of documents.
+  . Example Syntax: '''rord(myIndexedField)''' Example: '''rord(myDateField)''' is a metric
for how old a document is: the youngest document will return 1, the oldest document will return
the total number of documents.
  
  WARNING: as of Solr 1.4, ord() and rord() can cause excess memory use since they must use
a FieldCache entry at the top level reader, while sorting and function queries now use entries
at the segment level.  Hence sorting or using a different function query, in addition to ord()/rord()
will double memory use.
  
  == sum ==
  <!> [[Solr1.3]] sum(x,y,...) returns the sum of multiple functions.
  
+  . Example Syntax: '''sum(x,1)''' Example Syntax: '''sum(x,y)''' Example Syntax: '''sum(sqrt(x),log(y),z,0.5)'''
-  . Example Syntax: '''sum(x,1)'''
-  Example Syntax: '''sum(x,y)'''
-  Example Syntax: '''sum(sqrt(x),log(y),z,0.5)'''
  
  == sub ==
  <!> [[Solr1.4]] sub(x,y) returns x-y
  
+  . Example: '''sub(myfield,myfield2)''' Example: '''sub(100,sqrt(myfield))'''
-  . Example: '''sub(myfield,myfield2)'''
-  Example: '''sub(100,sqrt(myfield))'''
  
  == product ==
  <!> [[Solr1.3]] product(x,y,...) returns the product of multiple functions.
  
+  . Example Syntax: '''product(x,2)''' Example Syntax: '''product(x,y)'''
-  . Example Syntax: '''product(x,2)'''
-  Example Syntax: '''product(x,y)'''
  
  == div ==
  <!> [[Solr1.3]] div(x,y) divides the function x by the function y.
  
+  . Example Syntax: '''div(1,x)''' Example Syntax: '''div(sum(x,100),max(y,1))'''
-  . Example Syntax: '''div(1,x)'''
-  Example Syntax: '''div(sum(x,100),max(y,1))'''
  
  == pow ==
  <!> [[Solr1.3]] pow(x,y) raises the base x to the power y.
  
+  . Example Syntax: '''pow(x,0.5)'''   same as sqrt Example Syntax: '''pow(x,log(y))'''
-  . Example Syntax: '''pow(x,0.5)'''   same as sqrt
-  Example Syntax: '''pow(x,log(y))'''
  
  == abs ==
  <!> [[Solr1.3]] abs(x) returns the absolute value of a function.
  
+  . Example Syntax: '''abs(-5)''' Example Syntax: '''abs(x)'''
-  . Example Syntax: '''abs(-5)'''
-  Example Syntax: '''abs(x)'''
  
  == log ==
  <!> [[Solr1.3]] log(x) returns log base 10 of the function x.
  
+  . Example Syntax: '''log(x)''' Example Syntax: '''log(sum(x,100))'''
-  . Example Syntax: '''log(x)'''
-  Example Syntax: '''log(sum(x,100))'''
  
  == sqrt ==
  <!> [[Solr1.3]] sqrt(x) returns the square root of the function x
  
+  . Example Syntax: '''sqrt(2)''' Example Syntax: '''sqrt(sum(x,100))'''
-  . Example Syntax: '''sqrt(2)'''
-  Example Syntax: '''sqrt(sum(x,100))'''
  
  == map ==
  <!> [[Solr1.3]] map(x,min,max,target) maps any values of the function x that fall
within min and max inclusive to target.  min,max,target are constants. It outputs the field's
value if it does not fall between min and max.
  
-  . Example Syntax 1: '''map(x,0,0,1)'''  change any values of 0 to 1... useful in handling
default 0 values
-  Example Syntax 2 <!> [[Solr1.4]]: '''map(x,0,0,1,0)'''  change any values of 0 to
1 . and if the value is not zero it can be set to the value of the 5th argument instead of
defaulting to the field's value
+  . Example Syntax 1: '''map(x,0,0,1)'''  change any values of 0 to 1... useful in handling
default 0 values Example Syntax 2 <!> [[Solr1.4]]: '''map(x,0,0,1,0)'''  change any
values of 0 to 1 . and if the value is not zero it can be set to the value of the 5th argument
instead of defaulting to the field's value
  
  == scale ==
  <!> [[Solr1.3]] scale(x,minTarget,maxTarget) scales values of the function x such
that they fall between minTarget and maxTarget inclusive.
  
-  . Example Syntax: '''scale(x,1,2)'''  all values will be between 1 and 2 inclusive. NOTE:
The current implementation currently traverses all of the function values to obtain the min
and max so it can pick the correct scale.
-  NOTE: This implementation currently cannot distinguish when documents have been deleted
or documents that have no value, and 0.0 values will be used for these cases.  This means
that if values are normally all greater than 0.0, one can still end up with 0.0 as the min
value to map from.  In these cases, an appropriate map() function could be used as a workaround
to change 0.0 to a value in the real range.  example: '''scale(map(x,0,0,5),1,2)'''
+  . Example Syntax: '''scale(x,1,2)'''  all values will be between 1 and 2 inclusive. NOTE:
The current implementation currently traverses all of the function values to obtain the min
and max so it can pick the correct scale. NOTE: This implementation currently cannot distinguish
when documents have been deleted or documents that have no value, and 0.0 values will be used
for these cases.  This means that if values are normally all greater than 0.0, one can still
end up with 0.0 as the min value to map from.  In these cases, an appropriate map() function
could be used as a workaround to change 0.0 to a value in the real range.  example: '''scale(map(x,0,0,5),1,2)'''
  
  == query ==
  <!> [[Solr1.4]] query(subquery, default) returns the score for the given subquery,
or the default value for documents not matching the query.  Any type of subquery is supported
through either parameter dereferencing {{{$otherparam}}} or direct specification of the query
string in the LocalParams via "v".
  
+  . Example Syntax: '''q=product(popularity, query({!dismax v='solr rocks'})''' returns the
product of the popularity and the score of the dismax query. Example Syntax: '''q=product(popularity,
query($qq))&qq={!dismax}solr rocks''' is equivalent to the previous query, using param
dereferencing. Example Syntax: '''q=product(popularity, query($qq,0.1))&qq={!dismax}solr
rocks''' specifies a default score of 0.1 for documents that don't match the dismax query.
-  . Example Syntax: '''q=product(popularity, query({!dismax v='solr rocks'})''' returns the
product of the popularity and the score of the dismax query.
-  Example Syntax: '''q=product(popularity, query($qq))&qq={!dismax}solr rocks''' is equivalent
to the previous query, using param dereferencing.
-  Example Syntax: '''q=product(popularity, query($qq,0.1))&qq={!dismax}solr rocks'''
specifies a default score of 0.1 for documents that don't match the dismax query.
  
  == linear ==
  linear(x,m,c) implements m*x+c where m and c are constants and x is an arbitrary function.
 This is equivalent to '''sum(product(m,x),c)''', but slightly more efficient as it is implemented
as a single function.
@@ -155, +138 @@

  '''ms(a)'''
  
   . Returns the number of milliseconds since the epoch that the argument represents.
+  Example: '''ms(NOW/DAY)''' Example: '''ms(2000-01-01T00:00:00Z)''' Example: '''ms(mydatefield)'''
-  Example: '''ms(NOW/DAY)'''
-  Example: '''ms(2000-01-01T00:00:00Z)'''
-  Example: '''ms(mydatefield)'''
  
  '''ms(a,b)'''
  
-  . Returns the number of milliseconds that {{{b}}} occurs before {{{a}}} (i.e. {{{a - b}}}).
 Note that this offers higher precision than '''sub(a,b)''' because the arguments are not
converted to floating point numbers before subtraction.
+  . Returns the number of milliseconds that {{{b}}} occurs before {{{a}}} (i.e. {{{a - b}}}).
 Note that this offers higher precision than '''sub(a,b)''' because the arguments are not
converted to floating point numbers before subtraction. Example: '''ms(NOW,mydatefield)'''
Example: '''ms(mydatefield,2000-01-01T00:00:00Z)''' Example: '''ms(datefield1,datefield2)'''
-  Example: '''ms(NOW,mydatefield)'''
-  Example: '''ms(mydatefield,2000-01-01T00:00:00Z)'''
-  Example: '''ms(datefield1,datefield2)'''
  
  == dist ==
  [[Solr1.5]]
  
- Return the Distance between two Vectors (points) in an n-dimensional space.  See http://en.wikipedia.org/wiki/Lp_space
for more information.  Takes in the power, plus two or more !ValueSource instances and calculates
the distances between the two vectors.  Each !ValueSource must be a number.
+ Return the Distance between two Vectors (points) in an n-dimensional space.  See http://en.wikipedia.org/wiki/Lp_space
for more information.  Takes in the power, plus two or more !ValueSource instances and calculates
the distances between the two vectors.  Each !ValueSource must be a number.  There must be
an even number of !ValueSource instances passed in and the method assumes that the first half
represent the first vector and the second half represent the second vector.
+ 
+ Signature: dist(power, pointA, pointB, ...)
  
  Common cases:
  
-  ||<tablestyle="width: 467px; height: 88px;">Power ||Common Name ||
+  ||<tablewidth="467px" tableheight="88px" tablestyle="">Power ||Common Name ||
   ||0 ||Sparseness calculation ||
-  ||1||Manhattan (taxicab) Distance||
+  ||1 ||Manhattan (taxicab) Distance ||
-  ||2||Euclidean Distance||
+  ||2 ||Euclidean Distance ||
-  ||Infinite||Infinite norm - maximum value in the vector||
+  ||Infinite ||Infinite norm - maximum value in the vector ||
  
  
+ 
+ Example: Assume each document has 4 numeric fields: x,y,z,w.  Then we can calculate various
distances:
+ 
+  1. dist(2, x, y, 0, 0) - calculates the Euclidean distance between (0,0) and (x,y) for
each document
+ 
+  1. dist(1, x, y, 0, 0) - calculates the Manhattan distance between (0,0) and (x,y) for
each document
+ 
+  1. dist(2, x,y,z,0,0,0) - Euclidean distance between (0,0,0) and (x,y,z) for each document.
  
  === Date Boosting ===
  Boosting more recent content is a common use case.  One way is to use a {{{recip}}} function
in conjunction with {{{ms}}}.

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