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Posted to commits@pig.apache.org by gd...@apache.org on 2012/10/17 04:17:27 UTC
svn commit: r1399079 - in /pig/branches/branch-0.11: CHANGES.txt
src/docs/src/documentation/content/xdocs/basic.xml
Author: gdfm
Date: Wed Oct 17 02:17:27 2012
New Revision: 1399079
URL: http://svn.apache.org/viewvc?rev=1399079&view=rev
Log:
PIG-2947: Documentation for Rank operator (xalan via azaroth)
Modified:
pig/branches/branch-0.11/CHANGES.txt
pig/branches/branch-0.11/src/docs/src/documentation/content/xdocs/basic.xml
Modified: pig/branches/branch-0.11/CHANGES.txt
URL: http://svn.apache.org/viewvc/pig/branches/branch-0.11/CHANGES.txt?rev=1399079&r1=1399078&r2=1399079&view=diff
==============================================================================
--- pig/branches/branch-0.11/CHANGES.txt (original)
+++ pig/branches/branch-0.11/CHANGES.txt Wed Oct 17 02:17:27 2012
@@ -24,6 +24,7 @@ INCOMPATIBLE CHANGES
PIG-1891 Enable StoreFunc to make intelligent decision based on job success or failure (initialcontext via gates)
IMPROVEMENTS
+PIG-2947: Documentation for Rank operator (xalan via azaroth)
PIG-2943: DevTests, Refactor Windows checks to use new Util.WINDOWS method for code health (jgordon via dvryaboy)
Modified: pig/branches/branch-0.11/src/docs/src/documentation/content/xdocs/basic.xml
URL: http://svn.apache.org/viewvc/pig/branches/branch-0.11/src/docs/src/documentation/content/xdocs/basic.xml?rev=1399079&r1=1399078&r2=1399079&view=diff
==============================================================================
--- pig/branches/branch-0.11/src/docs/src/documentation/content/xdocs/basic.xml (original)
+++ pig/branches/branch-0.11/src/docs/src/documentation/content/xdocs/basic.xml Wed Oct 17 02:17:27 2012
@@ -6906,7 +6906,162 @@ DUMP X;
</source>
</section></section>
+ <!-- =================================================================== -->
+ <section id="rank">
+ <title>RANK</title>
+ <p>Returns each tuple with the rank within a relation.</p>
+
+ <section>
+ <title>Syntax</title>
+ <table>
+ <tr>
+ <td>
+ <p>alias = RANK alias [ BY { * [ASC|DESC] | field_alias [ASC|DESC] [, field_alias [ASC|DESC] â¦] } [DENSE] ];</p>
+ </td>
+ </tr>
+ </table>
+ </section>
+
+
+ <section>
+ <title>Terms</title>
+ <table>
+ <tr>
+ <td>
+ <p>alias</p>
+ </td>
+ <td>
+ <p>The name of a relation.</p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p>*</p>
+ </td>
+ <td>
+ <p>The designator for a tuple.</p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p>field_alias</p>
+ </td>
+ <td>
+ <p>A field in the relation. The field must be a simple type.</p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p>ASC</p>
+ </td>
+ <td>
+ <p>Sort in ascending order.</p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p>DESC</p>
+ </td>
+ <td>
+ <p>Sort in descending order.</p>
+ </td>
+ </tr>
+
+ <tr>
+ <td>
+ <p>DENSE</p>
+ </td>
+ <td>
+ <p>No gap in the ranking values. </p>
+ </td>
+ </tr>
+ </table>
+ </section>
+
+ <section>
+ <title>Usage</title>
+ <p>When specifying no field to sort on, the RANK operator simply prepends a sequential value to each tuple.</p>
+ <p>Otherwise, the RANK operator uses each field (or set of fields) to sort the relation. The rank of a tuple is one plus the number of different rank values preceding it. If two or more tuples tie on the sorting field values, they will receive the same rank.</p>
+ <p><strong>NOTE:</strong> When using the option <strong>DENSE</strong>, ties do not cause gaps in ranking values.</p>
+
+ </section>
+
+ <section>
+ <title>Examples</title>
+ <p>Suppose we have relation A.</p>
+ <source>
+A = load 'data' AS (f1:chararray,f2:int,f3:chararray);
+DUMP A;
+(David,1,N)
+(Tete,2,N)
+(Ranjit,3,M)
+(Ranjit,3,P)
+(David,4,Q)
+(David,4,Q)
+(Jillian,8,Q)
+(JaePak,7,Q)
+(Michael,8,T)
+(Jillian,8,Q)
+(Jose,10,V)
+ </source>
+ <p>In this example, the RANK operator does not change the order of the relation and simply prepends to each tuple a sequential value.</p>
+ <source>
+B = rank A;
+
+dump B;
+(1,David,1,N)
+(2,Tete,2,N)
+(3,Ranjit,3,M)
+(4,Ranjit,3,P)
+(5,David,4,Q)
+(6,David,4,Q)
+(7,Jillian,8,Q)
+(8,JaePak,7,Q)
+(9,Michael,8,T)
+(10,Jillian,8,Q)
+(11,Jose,10,V)
+ </source>
+
+ <p>In this example, the RANK operator works with f1 and f2 fields, and each one with different sorting order. RANK sorts the relation on these fields and
+ prepends the rank value to each tuple. Otherwise, the RANK operator uses each field (or set of fields) to sort the relation. The rank of a tuple is one plus the number of different rank values preceding it. If two or more tuples tie on the sorting field values, they will receive the same rank.</p>
+ <source>
+C = rank A by f1 DESC, f2 ASC;
+
+dump C;
+(1,Tete,2,N)
+(2,Ranjit,3,M)
+(2,Ranjit,3,P)
+(4,Michael,8,T)
+(5,Jose,10,V)
+(6,Jillian,8,Q)
+(6,Jillian,8,Q)
+(8,JaePak,7,Q)
+(9,David,1,N)
+(10,David,4,Q)
+(10,David,4,Q)
+ </source>
+
+ <p>Same example as previous, but DENSE. In this case there are no gaps in ranking values.</p>
+ <source>
+C = rank A by f1 DESC, f2 ASC DENSE;
+
+dump C;
+(1,Tete,2,N)
+(2,Ranjit,3,M)
+(2,Ranjit,3,P)
+(3,Michael,8,T)
+(4,Jose,10,V)
+(5,Jillian,8,Q)
+(5,Jillian,8,Q)
+(6,JaePak,7,Q)
+(7,David,1,N)
+(8,David,4,Q)
+(8,David,4,Q)
+ </source>
+
+ </section>
+ </section>
<!-- =========================================================================== -->