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hive使用技巧（一）自动化动态分配表分区及修改hive表字段名称
hive使用技巧（二）——共享中间结果集
hive使用技巧（三）——巧用group by实现去重统计

hive使用技巧（四）——巧用MapJoin解决数据倾斜问题

Hive使用技巧（五）—— 一行转多行,多行转一行

hive使用技巧（二）——共享中间结果集，很多hive的Job用到的中间结果集，存在“亲缘”关系，多作业用共用输入或输出。

1、优化前的SQL

SELECT
    COUNT(*) pv
FROM
    (
        SELECT
            cookieid,
            userid,
            to_date(DATETIME) day1
        FROM
            ods.tracklog_5min
        WHERE
            DAY>='20151001'
        AND DAY<='20151031'
        AND lower(requesturl) IN ('http://chat.hexun.com/',
                                  'http://zhibo.hexun.com/'))t1 

INNER JOIN
    (
        SELECT
            cookieid,
            to_date(DATETIME) day2
        FROM
            ods.tracklog_5min
        WHERE
            DAY>='20151001'
        AND DAY<='20151031'
        AND ((
                    lower(requesturl) LIKE 'http://zhibo.hexun.com/%'
                OR  lower(requesturl) LIKE 'http://chat.hexun.com/%')
            AND requesturl LIKE '%/default.html%'))t2
ON
    t1.cookieid=t2.cookieid
AND t1.day1=t2.day2
INNER JOIN
    (
        SELECT
            cookieid,
            to_date(DATETIME) day3
        FROM
            ods.tracklog_5min
        WHERE
            DAY>='20151001'
        AND DAY<='20151031'
        AND ( (
                    lower(requesturl) LIKE 'http://px.hexun.com/%'
                AND lower(requesturl) LIKE '%/default.html%' )
            OR  (
                    lower(requesturl) LIKE 'http://px.hexun.com/pack/%'
                AND lower(requesturl) LIKE '%.html%' )
            OR  (
                    lower(requesturl) LIKE 'http://px.hexun.com/p/%'
                AND lower(requesturl) LIKE '%.html%' ) ))t3
ON
    t1.cookieid=t3.cookieid
AND t1.day1=t3.day3
LEFT JOIN
    stage.saleplatform_productvisitdetail_temp t4
ON
    t1.userid=t4.userid
WHERE
    t4.createtime>t1.day1
OR  t4.userid IS NULL;

2、优化后的SQL

抽出公共数据

create table default.tracklog_10month as   
select * from  ods.tracklog_5min
WHERE  DAY>='20151001' AND DAY<='20151031';

SELECT
    COUNT(*) pv
FROM
    (
        SELECT
            cookieid,
            userid,
            to_date(DATETIME) day1
        FROM
            default.tracklog_10month 
        WHERE
             lower(requesturl) IN ('http://chat.hexun.com/',
                                  'http://zhibo.hexun.com/'))t1 

INNER JOIN
    (
       SELECT
            cookieid,
            to_date(DATETIME) day2
        FROM
            default.tracklog_10month 
        WHERE  (lower(requesturl) LIKE 'http://zhibo.hexun.com/%'
                OR  lower(requesturl) LIKE 'http://chat.hexun.com/%')
            AND requesturl LIKE '%/default.html%')t2
ON
    t1.cookieid=t2.cookieid
AND t1.day1=t2.day2
INNER JOIN
    (
        SELECT
            cookieid,
            to_date(DATETIME) day3
        FROM
            default.tracklog_10month
        WHERE        
        ( (
                    lower(requesturl) LIKE 'http://px.hexun.com/%'
                AND lower(requesturl) LIKE '%/default.html%' )
            OR  (
                    lower(requesturl) LIKE 'http://px.hexun.com/pack/%'
                AND lower(requesturl) LIKE '%.html%' )
            OR  (
                    lower(requesturl) LIKE 'http://px.hexun.com/p/%'
                AND lower(requesturl) LIKE '%.html%' ) ))t3
ON
    t1.cookieid=t3.cookieid
AND t1.day1=t3.day3
LEFT JOIN
    stage.saleplatform_productvisitdetail_temp t4
ON
    t1.userid=t4.userid
WHERE
    t4.createtime>t1.day1
OR  t4.userid IS NULL;

本质就是降IO，减少MR阶段中大量读写磁盘及网络IO的压力。