pig-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Apache Wiki <wikidi...@apache.org>
Subject [Pig Wiki] Update of "PigLatin" by OlgaN
Date Tue, 16 Oct 2007 20:08:26 GMT
Dear Wiki user,

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

The following page has been changed by OlgaN:
http://wiki.apache.org/pig/PigLatin

------------------------------------------------------------------------------
  || Map Lookup against another data item || f3#'apache' || Data Atom 'pig' || User's responsibility
to ensure that a lookup is written only against a  data map, otherwise a runtime error is
thrown. If the key being looked up does not exist, a Data Atom with an empty string is returned
||
  || Function applied to another data item || SUM(f2.$0) || 2+4+5 = 11 || SUM is a builtin
Pig function. See PigFunctions for how to write your own functions ||
  || Infix Expression of other data items || COUNT(f2) + f1 / '2.0' || 3 + 1 / 2.0 = 3.5 ||
||
+ || Bincond, i.e., the value of the data item is chosen according to some condition ||(f1
= =  '1' ? '2' : COUNT(f2))|| '2' since f1=='1' is true. If f1 were != '1', then the value
of this data item for t would be COUNT(f2)=3 || See [#CondS Conditions] for what the format
of the condition in the bincond can be ||
  
+ == Pig Latin Statements ==
+ 
+ A Pig Latin statement is a command that produces a '''Relation'''. A relation is simply
a data bag with a name. That name is called the relation's '''alias'''. The simplest Pig Latin
statement is LOAD, which reads a relation from a file in the file system. Other Pig Latin
statements process one or more input relations, and produce a new relation as a result.
+ 
+ Pig commands can span multiple lines and must include ";" at the end.
+ 
+ Examples:
+ 
+ `grunt> A = load 'data' using PigStorage() as (x, y, z);`
+ `grunt>B = group A by x;`
+ `grunt> C = foreach B {`
+ 
+ `D = distinct A.y;`
+ 
+ `generate flatten(group), COUNT(D);`
+ 
+ `}`
+ `grunt>` 
+ 

Mime
View raw message