pig询问top k，每个返回hour和ad_network_id最大的两个记录（SUBSTRING，order，COUNT_STAR，limit）

pig里面有一个TOP功能。我不知道为什么用不了。有时间去看看pig源代码。

SET job.name 'top_k';

SET job.priority HIGH;

--REGISTER piggybank.jar;

REGISTER wizad-etl-udf-0.1.jar;

--DEFINE SequenceFileLoader org.apache.pig.piggybank.storage.SequenceFileLoader();

DEFINE SequenceFileLoader com.vpon.wizad.etl.pig.SequenceFileCSVLoader();

--%default cleanedLog /user/wizad/data/wizad/cleaned/2014-07-30/*/part*

%default cleanedLog /user/wizad/data/wizad/cleaned/$date/*/part*

%default output_path /user/wizad/tmp/hour_count

origin_cleaned_data = LOAD '$cleanedLog' USING SequenceFileLoader

AS (ad_network_id:chararray,

wizad_ad_id:chararray,

guid:chararray,

id:chararray,

create_time:chararray,

action_time:chararray,

log_type:chararray,

ad_id:chararray,

positioning_method:chararray,

location_accuracy:chararray,

lat:chararray,

lon:chararray,

cell_id:chararray,

lac:chararray,

mcc:chararray,

mnc:chararray,

ip:chararray,

connection_type:chararray,

imei:chararray,

android_id:chararray,

android_advertising_id:chararray,

udid:chararray,

openudid:chararray,

idfa:chararray,

mac_address:chararray,

uid:chararray,

density:chararray,

screen_height:chararray,

screen_width:chararray,

user_agent:chararray,

app_id:chararray,

app_category_id:chararray,

device_model_id:chararray,

carrier_id:chararray,

os_id:chararray,

device_type:chararray,

os_version:chararray,

country_region_id:chararray,

province_region_id:chararray,

city_region_id:chararray,

ip_lat:chararray,

ip_lon:chararray,

quadkey:chararray);

show_log= FILTER origin_cleaned_data by log_type=='1';

--extract column for analyzing。提取子字段做为新属性

original_hour = FOREACH show_log GENERATE ad_network_id,wizad_ad_id,guid,app_category_id,log_type,SUBSTRING(create_time,11,13) AS hour; --(wizad_ad_id,guid,log_type,hour)

hour_group = GROUP original_hour BY (hour,app_category_id);--按属性分类，

hour_count = foreach hour_group{

--guid_data = $1.guid;

--uniq_guid = distinct guid_data;--去重处理。

查唯一个数。

ad_network_ids = original_hour.ad_network_id;

uniq_ad_network_ids = distinct ad_network_ids;

--统计每一个包下的个数，将后面uniq_ad_network_ids分成单个记录。

比方，uniq_ad_network_ids原值{3,5}，现变成两条记录，分为（xx，3）（xx，5）两条记录

generate flatten(group), COUNT_STAR($1) AS pv, flatten(uniq_ad_network_ids);

}

describe hour_count;

--查看结构为：hour_count: {group::hour: chararray,group::app_category_id: chararray,pv: long,uniq_ad_network_ids::ad_network_id: chararray}

group_hour_count = group hour_count by (hour,ad_network_id);

top_2_data = foreach group_hour_count {

--top_dataset = TOP(2,hour_count.pv, hour_count);--top函数 不能用。有谁用过告诉一声。我就不用看源代码拉，哈哈

--hour_data = hour_count;

--top k实现方式。order排序，limit返回前k个。

order_hour_count = order hour_count by pv DESC;

top2_hour_count = limit order_hour_count 2;

--generate group, top2_hour_count.pv, top2_hour_count.app_category_id;-- 注意，后面是两个bag。分开的。

generate flatten(top2_hour_count );

}