Spark非常实用的窗口函数
spark 累加历史主要用到了窗口函数，而进行全部统计，则需要用到rollup函数
1 应用场景：
1、我们需要统计用户的总使用时长（累加历史）
2、前台展现页面需要对多个维度进行查询，如：产品、地区等等
3、需要展现的表格头如： 产品、2015-04、2015-05、2015-06
2 原始数据：
| product_code | event_date | duration |
|---|---|---|
| 1438 | 2016-05-13 | 165 |
| 1438 | 2016-05-14 | 595 |
| 1438 | 2016-05-15 | 105 |
| 1629 | 2016-05-13 | 12340 |
| 1629 | 2016-05-14 | 13850 |
| 1629 | 2016-05-15 | 227 |
3 业务场景实现
3.1 业务场景1：累加历史：
如数据源所示：我们已经有当天用户的使用时长，我们期望在进行统计的时候，14号能累加13号的，15号能累加14、13号的，以此类推
3.1.1 spark-sql实现
//spark sql 使用窗口函数累加历史数据
sqlContext.sql(
"""
select pcode,event_date,sum(duration) over (partition by pcode order by event_date asc) as sum_duration
from userlogs_date
""").show
+-----+----------+------------+
|pcode|event_date|sum_duration|
+-----+----------+------------+
| 1438|2016-05-13| 165|
| 1438|2016-05-14| 760|
| 1438|2016-05-15| 865|
| 1629|2016-05-13| 12340|
| 1629|2016-05-14| 26190|
| 1629|2016-05-15| 26417|
+-----+----------+------------+
3.1.2 dataframe实现
//使用Column提供的over 函数，传入窗口操作
import org.apache.spark.sql.expressions._
val first_2_now_window = Window.partitionBy("pcode").orderBy("event_date")
df_userlogs_date.select(
$"pcode",
$"event_date",
sum($"duration").over(first_2_now_window).as("sum_duration")
).show
+-----+----------+------------+
|pcode|event_date|sum_duration|
+-----+----------+------------+
| 1438|2016-05-13| 165|
| 1438|2016-05-14| 760|
| 1438|2016-05-15| 865|
| 1629|2016-05-13| 12340|
| 1629|2016-05-14| 26190|
| 1629|2016-05-15| 26417|
+-----+----------+------------+
3.1.3 扩展 累加一段时间范围内
实际业务中的累加逻辑远比上面复杂，比如，累加之前N天，累加前N天到后N天等等。以下我们来实现：
3.1.3.1 累加历史所有：
select pcode,event_date,sum(duration) over (partition by pcode order by event_date asc) as sum_duration from userlogs_date
select pcode,event_date,sum(duration) over (partition by pcode order by event_date asc rows between unbounded preceding and current row) as sum_duration from userlogs_date
Window.partitionBy("pcode").orderBy("event_date").rowsBetween(Long.MinValue,0)
Window.partitionBy("pcode").orderBy("event_date")
上边四种写法完全相等
3.1.3.2 累加N天之前，假设N=3
//如果，不想要分区，想从每月的第一天累加的当前天 可以去掉partition
select pcode,event_date,sum(duration) over (partition by pcode order by
event_date asc rows between 3 preceding and current row) as sum_duration
from userlogs_date
Window.partitionBy("pcode").orderBy("event_date").rowsBetween(-3,0)
3.1.3.3 累加前N天，后M天: 假设N=3 M=5
select pcode,event_date,sum(duration) over (partition by pcode order by
event_date asc rows between 3 preceding and 5 following ) as sum_duration
from userlogs_date
Window.partitionBy("pcode").orderBy("event_date").rowsBetween(-3,5)
3.1.3.4 累加该分区内所有行
select pcode,event_date,sum(duration) over (partition by pcode order by
event_date asc rows between unbounded preceding and unbounded following )
as sum_duration from userlogs_date
Window.partitionBy("pcode").orderBy("event_date").rowsBetween
(Long.MinValue,Long.MaxValue)
总结如下：
preceding：用于累加前N行（分区之内）。若是从分区第一行头开始，则为 unbounded。 N为：相对当前行向前的偏移量
following ：与preceding相反，累加后N行（分区之内）。若是累加到该分区结束，则为 unbounded。N为：相对当前行向后的偏移量
current row：顾名思义，当前行，偏移量为0
说明：上边的前N，后M，以及current row均会累加该偏移量所在行
3.1.3.4 实测结果
累加历史：分区内当天及之前所有 写法
1：select pcode,event_date,sum(duration) over (partition by pcode order by
event_date asc) as sum_duration from userlogs_date
+-----+----------+------------+
|pcode|event_date|sum_duration|
+-----+----------+------------+
| 1438|2016-05-13| 165|
| 1438|2016-05-14| 760|
| 1438|2016-05-15| 865|
| 1629|2016-05-13| 12340|
| 1629|2016-05-14| 26190|
| 1629|2016-05-15| 26417|
+-----+----------+------------+
累加历史：分区内当天及之前所有 写法2：
select pcode,event_date,sum(duration) over (partition by pcode order by
event_date asc rows between unbounded preceding and current row) as
sum_duration from userlogs_date
+-----+----------+------------+
|pcode|event_date|sum_duration|
+-----+----------+------------+
| 1438|2016-05-13| 165|
| 1438|2016-05-14| 760|
| 1438|2016-05-15| 865|
| 1629|2016-05-13| 12340|
| 1629|2016-05-14| 26190|
| 1629|2016-05-15| 26417|
+-----+----------+------------+
累加当日和昨天：
select pcode,event_date,sum(duration) over (partition by pcode order by
event_date asc rows between 1 preceding and current row) as sum_duration
from userlogs_date
+-----+----------+------------+
|pcode|event_date|sum_duration|
+-----+----------+------------+
| 1438|2016-05-13| 165|
| 1438|2016-05-14| 760|
| 1438|2016-05-15| 700|
| 1629|2016-05-13| 12340|
| 1629|2016-05-14| 26190|
| 1629|2016-05-15| 14077|
+-----+----------+------------+
累加当日、昨日、明日：
select pcode,event_date,sum(duration) over (partition by pcode order by
event_date asc rows between 1 preceding and 1 following ) as sum_duration
from userlogs_date
+-----+----------+------------+
|pcode|event_date|sum_duration|
+-----+----------+------------+
| 1438|2016-05-13| 760|
| 1438|2016-05-14| 865|
| 1438|2016-05-15| 700|
| 1629|2016-05-13| 26190|
| 1629|2016-05-14| 26417|
| 1629|2016-05-15| 14077|
+-----+----------+------------+
累加分区内所有：当天和之前之后所有：
select pcode,event_date,sum(duration) over (partition by pcode order by
event_date asc rows between unbounded preceding and unbounded following )
as sum_duration from userlogs_date
+-----+----------+------------+
|pcode|event_date|sum_duration|
+-----+----------+------------+
| 1438|2016-05-13| 865|
| 1438|2016-05-14| 865|
| 1438|2016-05-15| 865|
| 1629|2016-05-13| 26417|
| 1629|2016-05-14| 26417|
| 1629|2016-05-15| 26417|
+-----+----------+------------+
3.2 业务场景2：统计全部
3.2.1 spark sql实现
//spark sql 使用rollup添加all统计
sqlContext.sql(
"""
select pcode,event_date,sum(duration) as sum_duration
from userlogs_date_1
group by pcode,event_date with rollup
order by pcode,event_date
""").show()
+-----+----------+------------+
|pcode|event_date|sum_duration|
+-----+----------+------------+
| null| null| 27282|
| 1438| null| 865|
| 1438|2016-05-13| 165|
| 1438|2016-05-14| 595|
| 1438|2016-05-15| 105|
| 1629| null| 26417|
| 1629|2016-05-13| 12340|
| 1629|2016-05-14| 13850|
| 1629|2016-05-15| 227|
+-----+----------+------------