1 创建数据
from pyspark.sql import *
from pyspark.sql import functions as F
Employee = Row("firstName", "lastName", "email", "salary","depid")
employee1 = Employee('Basher', 'armbrust', 'bash@edureka.co', 100000,1)
employee2 = Employee('Daniel', 'meng', 'daniel@stanford.edu', 120000,1 )
employee3 = Employee('Muriel', None, 'muriel@waterloo.edu', 140000 ,2)
employee4 = Employee('Rachel', 'wendell', 'rach_1@edureka.co', 160000,3)
employee5 = Employee('Rachel', 'galifianakis', 'rach_2@edureka.co', 160000,4 )
df_employee = spark.createDataFrame((employee1,employee2,employee3,employee4,employee5))
# cache 一下，避免反复运行
df_employee.cache()
df_employee.count()
>>> df_employee.show()
+---------+------------+-------------------+------+-----+
|firstName| lastName| email|salary|depid|
+---------+------------+-------------------+------+-----+
| Basher| armbrust| bash@edureka.co|100000| 1|
| Daniel| meng|daniel@stanford.edu|120000| 1|
| Muriel| null|muriel@waterloo.edu|140000| 2|
| Rachel| wendell| rach_1@edureka.co|160000| 3|
| Rachel|galifianakis| rach_2@edureka.co|160000| 4|
+---------+------------+-------------------+------+-----+
2 Distinct 去重
df_employee.select('firstName').distinct().show()
+---------+
|firstName|
+---------+
| Muriel|
| Basher|
| Rachel|
| Daniel|
+---------+
>>> df_employee.select('firstName','salary').distinct().show()
+---------+------+
|firstName|salary|
+---------+------+
| Rachel|160000|
| Muriel|140000|
| Daniel|120000|
| Basher|100000|
+---------+------+
# select count(distinct(firstName)) from employee
df_employee.select('firstName').distinct().count()
3 聚合Group by
# select depid,count(1) as count from employee group by depid
df_employee.groupby('depid').count().show()
# group by 多个字段
df_employee.groupby('depid','firstName').count().show()
+-----+---------+-----+
|depid|firstName|count|
+-----+---------+-----+
| 1| Basher| 1|
| 3| Rachel| 1|
| 4| Rachel| 1|
| 2| Muriel| 1|
| 1| Daniel| 1|
+-----+---------+-----+
# group by 聚合sum
# select depid,firstName,sum(salary) from employee group by depid,firstName;
>>> df_employee.groupby('depid','firstName').sum('salary').show()
+-----+---------+-----------+
|depid|firstName|sum(salary)|
+-----+---------+-----------+
| 1| Basher| 100000|
| 3| Rachel| 160000|
| 4| Rachel| 160000|
| 2| Muriel| 140000|
| 1| Daniel| 120000|
+-----+---------+-----------+
# 可以看到sum(salary)这个name非常不合理，有没有办法提供alias
df_employee.groupby('depid','firstName').agg(F.sum(F.col('salary')).alias('total_salary')).show()
# agg 这个接口更通用，多个groupby指标，也可以使用
agg_stat = [
F.sum(F.col('salary')).alias('total_salary'),
F.max(F.col('salary')).alias('max_salary'),
F.count(F.col('salary')).alias('n')
]
df_employee.groupby('depid').agg(*agg_stat).show()
+-----+------------+----------+---+
|depid|total_salary|max_salary| n|
+-----+------------+----------+---+
| 1| 220000| 120000| 2|
| 3| 160000| 160000| 1|
| 2| 140000| 140000| 1|
| 4| 160000| 160000| 1|
+-----+------------+----------+---+
4 Filter/ Where 按条件删选
>>> df_employee.filter(df_employee.firstName=='Rachel').show()
+---------+------------+-----------------+------+
|firstName| lastName| email|salary|
+---------+------------+-----------------+------+
| Rachel| wendell|rach_1@edureka.co|160000|
| Rachel|galifianakis|rach_2@edureka.co|160000|
+---------+------------+-----------------+------+
## 下面的方式也是可以的
from pyspark.sql import functions as F
df_employee.filter(F.col('firstName')=='Rachel').show()
# 多个条件 and: & or: |
>>> df_employee.filter((F.col('firstName')=='Rachel') | (F.col('firstName')=='Muriel')).show()
+---------+------------+-------------------+------+
|firstName| lastName| email|salary|
+---------+------------+-------------------+------+
| Muriel| null|muriel@waterloo.edu|140000|
| Rachel| wendell| rach_1@edureka.co|160000|
| Rachel|galifianakis| rach_2@edureka.co|160000|
+---------+------------+-------------------+------+
# and
df_employee.filter((F.col('firstName')=='Rachel') & (F.col('lastName')=='wendell')).show()
# filter 太长了，简略一些
filters = (F.col('firstName')=='Rachel') & (F.col('lastName')=='wendell')
df_employee.filter(filters).show()
# filters 再长一点怎么办，分行写
filters = (
(
(F.col('firstName')=='Rachel')
|
(F.col('lastName')=='wendell')
) & (F.col('salary') > 140000)
)
df_employee.filter(filters).show()
# 直接传字符串
df_employee.filter('(firstName=="Rachel" or lastName is null) or firstName=="Daniel"').show()
+---------+------------+-------------------+------+-----+
|firstName| lastName| email|salary|depid|
+---------+------------+-------------------+------+-----+
| Daniel| meng|daniel@stanford.edu|120000| 1|
| Muriel| null|muriel@waterloo.edu|140000| 2|
| Rachel| wendell| rach_1@edureka.co|160000| 3|
| Rachel|galifianakis| rach_2@edureka.co|160000| 4|
+---------+------------+-------------------+------+-----+
# where 等同于filter
df_employee.where('salary>140000').show()
5 排序Order By
df_employee.orderBy('salary',ascending=False)
## 多个字段
df_employee.orderBy(['firstName','salary'],ascending=True).show()
## 多个字段排序方式不同
df_employee.orderBy([F.col('firstName').desc(),F.col('salary').asc()]).show()
## 更简单的方式
df_employee.orderBy([F.desc('firstName'),F.asc('salary')]).show()
6 Join
# 创建表
department1 = Row(id=1, name='HR',bonus=0.2)
department2 = Row(id=2, name='OPS',bonus=0.3)
department3 = Row(id=3, name='FN',bonus=0.3)
department4 = Row(id=4, name='DEV',bonus=0.35)
department5 = Row(id=5, name='AD',bonus=0.21)
df_dep = spark.createDataFrame((department1,department2,department3,department4,department5))
df_dep.cache()
df_dep.count()
>>> df_dep.show()
+-----+---+----+
|bonus| id|name|
+-----+---+----+
| 0.2| 1| HR|
| 0.3| 2| OPS|
| 0.3| 3| FN|
| 0.35| 4| DEV|
| 0.21| 5| AD|
+-----+---+----+
# 默认inner join
>>> df_employee.join(df_dep,df_dep.id==df_employee.depid).show()
+---------+------------+-------------------+------+-----+-----+---+----+
|firstName| lastName| email|salary|depid|bonus| id|name|
+---------+------------+-------------------+------+-----+-----+---+----+
| Basher| armbrust| bash@edureka.co|100000| 1| 0.2| 1| HR|
| Daniel| meng|daniel@stanford.edu|120000| 1| 0.2| 1| HR|
| Muriel| null|muriel@waterloo.edu|140000| 2| 0.3| 2| OPS|
| Rachel| wendell| rach_1@edureka.co|160000| 3| 0.3| 3| FN|
| Rachel|galifianakis| rach_2@edureka.co|160000| 4| 0.35| 4| DEV|
+---------+------------+-------------------+------+-----+-----+---+----+
# outer join
>>> df_employee.join(df_dep,df_dep.id==df_employee.depid,how='outer').show()
+---------+------------+-------------------+------+-----+-----+---+----+
|firstName| lastName| email|salary|depid|bonus| id|name|
+---------+------------+-------------------+------+-----+-----+---+----+
| null| null| null| null| null| 0.21| 5| AD|
| Basher| armbrust| bash@edureka.co|100000| 1| 0.2| 1| HR|
| Daniel| meng|daniel@stanford.edu|120000| 1| 0.2| 1| HR|
| Rachel| wendell| rach_1@edureka.co|160000| 3| 0.3| 3| FN|
| Muriel| null|muriel@waterloo.edu|140000| 2| 0.3| 2| OPS|
| Rachel|galifianakis| rach_2@edureka.co|160000| 4| 0.35| 4| DEV|
+---------+------------+-------------------+------+-----+-----+---+----+
# 还可选 left_outer, right_outer, leftsemi,
# 另，如果join的key相同，可以直接传入column name
df1.join(df2, ['id1','id2']).show()
问题记录
1 partition 字段首字母消失
dataframe 通过 partition存储后，再读回来，发现原来的partition首字母会被忽略。如"0100" 成了 100
原因是，spark有类型推断，如果字符串像数值，则转为了数值。之后再进行统一类型为字符。
所以，如果出现这种情况，请关闭这个开关
spark.conf.set('spark.sql.sources.partitionColumnTypeInference.enabled','false')
