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From Apache Wiki <wikidi...@apache.org>
Subject [Pig Wiki] Trivial Update of "PigTutorial" by CorinneC
Date Mon, 09 Jun 2008 18:55:36 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 CorinneC:
http://wiki.apache.org/pig/PigTutorial

------------------------------------------------------------------------------
  
  The tutorial pig script (tutorial.pig or tutorial-local.pig) does the following:
  
+ 
-  * Registers the tutorial JAR file so that the user-defined functions (UDFs) can be called
in the script. 
+  * Register the tutorial JAR file so that the included UDFs can be called in the script.
+ {{{ 
+ REGISTER ./tutorial.jar; 
+ }}}
+ 
+ 
-  * Uses the [http://wiki.apache.org/pig/PigBuiltins PigStorage] function to load the excite
log file (excite.log or excite-small.log) into the “raw” bag as an array of records with
the fields '''user''', '''time''', and '''query'''. 
+  * Use the [http://wiki.apache.org/pig/PigBuiltins PigStorage] function to load the excite
log file (excite.log or excite-small.log) into the “raw” bag as an array of records with
the fields '''user''', '''time''', and '''query'''. Input: (user,time,query) 
+ {{{
+ raw = LOAD 'excite.log' USING PigStorage('\t') AS (user, time, query);
+ }}}
+ 
-  * Calls the NonURLDetector UDF to remove records if the query field is empty or a URL.

+  * Call the NonURLDetector UDF to remove records if the query field is empty or a URL. 
+ {{{ 
+ clean1 = FILTER raw BY org.apache.pig.tutorial.NonURLDetector(query);
+ }}}
+ 
-  * Calls the !ToLower UDF to change the query field to lowercase.
+  * Call the !ToLower UDF to change the query field to lowercase. 
+ {{{ 
+ clean2 = FOREACH clean1 GENERATE user, time, org.apache.pig.tutorial.ToLower(query) as query;
+ }}}
+ 
-  * Calls the !NonPornDetector UDF to remove records if the query field contains porn terms.

+  * Call the !NonPornDetector UDF to remove records if the query field contains porn terms.

-  * Calls the !ExtractHour UDF to extract the hour from the time field.
+ {{{ 
+ clean3 = FILTER clean2 BY org.apache.pig.tutorial.NonPornDetector(query);
+ }}}
+ 
+  * Because the log file only contains queries for a single day, we are only interested in
the hour. The excite query log timestamp format is YYMMDDHHMMSS. Call the !ExtractHour UDF
to extract the hour (HH) from the time field.
+ {{{ 
+ houred = FOREACH clean3 GENERATE user, org.apache.pig.tutorial.ExtractHour(time) as hour,
query;
+ }}}
+ 
-  * Calls the N!GramGenerator UDF to compose the n-grams of the query. 
+  * Call the N!GramGenerator UDF to compose the n-grams of the query.
+ {{{ 
+ ngramed1 = FOREACH houred GENERATE user, hour, flatten(org.apache.pig.tutorial.NGramGenerator(query))
as ngram;
+ }}}
+ 
-  * Uses the [http://wiki.apache.org/pig/PigLatin#DISTINCT:_Eliminating_duplicates_in_data
DISTINCT] command to get the unique n-grams for all records. 
+  * Use the [http://wiki.apache.org/pig/PigLatin#DISTINCT:_Eliminating_duplicates_in_data
DISTINCT] command to get the unique n-grams for all records. 
+ {{{ 
+ ngramed2 = DISTINCT ngramed1;
+ }}}
+ 
-  * Uses the [http://wiki.apache.org/pig/PigLatin#COGROUP:_Getting_the_relevant_data_together
GROUP] command to group records by n-gram and hour.
+  * Use the [http://wiki.apache.org/pig/PigLatin#COGROUP:_Getting_the_relevant_data_together
GROUP] command to group records by n-gram and hour.
+ {{{ 
+ hour_frequency1 = GROUP ngramed2 BY (ngram, hour);
+ }}}
+ 
-  * Uses the [http://wiki.apache.org/pig/PigBuiltins COUNT] function to get the count (occurrences)
of each n-gram.
+  * Use the [http://wiki.apache.org/pig/PigBuiltins COUNT] function to get the count (occurrences)
of each n-gram. 
+ {{{ 
+ hour_frequency2 = FOREACH hour_frequency1 GENERATE flatten($0), COUNT($1) as count;
+ }}}
+ 
-  * Uses the [http://wiki.apache.org/pig/PigLatin#COGROUP:_Getting_the_relevant_data_together
GROUP] command to group records by n-gram only.
+  * Use the [http://wiki.apache.org/pig/PigLatin#COGROUP:_Getting_the_relevant_data_together
GROUP] command to group records by n-gram only. Each group now corresponds to a distinct n-gram
and has the count for each hour.
-  * Calls the !ScoreGenerator UDF to calculate a "popularity" score for the n-gram.
+ {{{ 
+ uniq_frequency1 = GROUP hour_frequency2 BY group::ngram;
+ }}}
+ 
+  * For each group, identify the hour in which this n-gram is used with a particularly high
frequency. Call the !ScoreGenerator UDF to calculate a "popularity" score for the n-gram.
+ {{{ 
+ uniq_frequency2 = FOREACH uniq_frequency1 GENERATE flatten($0), flatten(org.apache.pig.tutorial.ScoreGenerator($1));
+ }}}
+ 
-  * Uses the [http://wiki.apache.org/pig/PigLatin#FOREACH_..._GENERATE:_Applying_transformations_to_the_data
FOREACH-GENERATE] command to assign names to the fields.
+  * Use the [http://wiki.apache.org/pig/PigLatin#FOREACH_..._GENERATE:_Applying_transformations_to_the_data
FOREACH-GENERATE] command to assign names to the fields. 
+ {{{ 
+ uniq_frequency3 = FOREACH uniq_frequency2 GENERATE $1 as hour, $0 as ngram, $2 as score,
$3 as count, $4 as mean;
+ }}}
+ 
-  * Uses the [http://wiki.apache.org/pig/PigLatin#FILTER:_Getting_rid_of_data_you_are_not_interested_in_
FILTER] command to move all records with a score less than or equal to 2.0.
+  * Use the [http://wiki.apache.org/pig/PigLatin#FILTER:_Getting_rid_of_data_you_are_not_interested_in_
FILTER] command to move all records with a score less than or equal to 2.0.
+ {{{ 
+ filtered_uniq_frequency = FILTER uniq_frequency3 BY score > 2.0;
+ }}}
+ 
-  * Uses the [http://wiki.apache.org/pig/PigLatin#ORDER:_Sorting_data_according_to_some_field
ORDER] command to sort the remaining records by hour and score.
+  * Use the [http://wiki.apache.org/pig/PigLatin#ORDER:_Sorting_data_according_to_some_field
ORDER] command to sort the remaining records by hour and score. 
+ {{{ 
+ ordered_uniq_frequency = ORDER filtered_uniq_frequency BY (hour, score);
+ }}}
+ 
-  * Uses the [http://wiki.apache.org/pig/PigBuiltins PigStorage] function to store the results.
The output file contains a list of n-grams with the following fields: '''hour''', '''ngram''',
'''score''', '''count''', '''mean''' 
+  * Use the [http://wiki.apache.org/pig/PigBuiltins PigStorage] function to store the results.
The output file contains a list of n-grams with the following fields: '''hour''', '''ngram''',
'''score''', '''count''', '''mean''' Output: (hour, n-gram, score, count, average_counts_among_all_hours)
- 
+ {{{ 
+ STORE ordered_uniq_frequency INTO '/tmp/tutorial-results' USING PigStorage(); 
+ }}}
  
  [[Anchor(Tutorial_Join_Pig_Script)]]
  == Tutorial-Join Pig Script ==

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