如何使用ApacheSpark数据帧(Python)执行Switch语句
我试图对我的数据执行一个操作,如果某个值与某个条件匹配,则该值将映射到一个预定义值列表,否则映射到一个默认值列表 这将是等效的SQL:如何使用ApacheSpark数据帧(Python)执行Switch语句,python,apache-spark,dataframe,pyspark,apache-spark-sql,Python,Apache Spark,Dataframe,Pyspark,Apache Spark Sql,我试图对我的数据执行一个操作,如果某个值与某个条件匹配,则该值将映射到一个预定义值列表,否则映射到一个默认值列表 这将是等效的SQL: CASE WHEN user_agent LIKE \'%CanvasAPI%\' THEN \'api\' WHEN user_agent LIKE \'%candroid%\' THEN \'mobile_app_android\' WHEN user_agent LIKE \'%iCa
CASE
WHEN user_agent LIKE \'%CanvasAPI%\' THEN \'api\'
WHEN user_agent LIKE \'%candroid%\' THEN \'mobile_app_android\'
WHEN user_agent LIKE \'%iCanvas%\' THEN \'mobile_app_ios\'
WHEN user_agent LIKE \'%CanvasKit%\' THEN \'mobile_app_ios\'
WHEN user_agent LIKE \'%Windows NT%\' THEN \'desktop\'
WHEN user_agent LIKE \'%MacBook%\' THEN \'desktop\'
WHEN user_agent LIKE \'%iPhone%\' THEN \'mobile\'
WHEN user_agent LIKE \'%iPod Touch%\' THEN \'mobile\'
WHEN user_agent LIKE \'%iPad%\' THEN \'mobile\'
WHEN user_agent LIKE \'%iOS%\' THEN \'mobile\'
WHEN user_agent LIKE \'%CrOS%\' THEN \'desktop\'
WHEN user_agent LIKE \'%Android%\' THEN \'mobile\'
WHEN user_agent LIKE \'%Linux%\' THEN \'desktop\'
WHEN user_agent LIKE \'%Mac OS%\' THEN \'desktop\'
WHEN user_agent LIKE \'%Macintosh%\' THEN \'desktop\'
ELSE \'other_unknown\'
END AS user_agent_type
我是Spark的新手,因此我在这个程序中的第一次尝试使用查找字典并在RDD中逐行调整值,如下所示:
我当前的代码将数据放在数据帧中,我不确定如何最有效地执行上述操作。我知道它们是不可变的,所以它需要作为新的数据帧返回,但我的问题是如何最好地做到这一点。这是我的密码:
from boto3 import client
import psycopg2 as ppg2
from pyspark import SparkConf, SparkContext
from pyspark.sql import SQLContext
from pyspark.sql.functions import current_date, date_format, lit, StringType
EMR_CLIENT = client('emr')
conf = SparkConf().setAppName('Canvas Requests Logs')
sc = SparkContext(conf=conf)
sql_context = SQLContext(sc)
# for dependencies
# sc.addPyFile()
USER_AGENT_VALS = {
'CanvasAPI': 'api',
'candroid': 'mobile_app_android',
'iCanvas': 'mobile_app_ios',
'CanvasKit': 'mobile_app_ios',
'Windows NT': 'desktop',
'MacBook': 'desktop',
'iPhone': 'mobile',
'iPod Touch': 'mobile',
'iPad': 'mobile',
'iOS': 'mobile',
'CrOS': 'desktop',
'Android': 'mobile',
'Linux': 'desktop',
'Mac OS': 'desktop',
'Macintosh': 'desktop'
}
if __name__ == '__main__':
df = sql_context.read.parquet(
r'/Users/mharris/PycharmProjects/etl3/pyspark/Datasets/'
r'usage_data.gz.parquet')
course_data = df.filter(df['context_type'] == 'Course')
request_data = df.select(
df['user_id'],
df['context_id'].alias('course_id'),
date_format(df['request_timestamp'], 'MM').alias('request_month'),
df['user_agent']
)
sesh_id_data = df.groupBy('user_id').count()
joined_data = request_data.join(
sesh_id_data,
on=request_data['user_id'] == sesh_id_data['user_id']
).drop(sesh_id_data['user_id'])
all_fields = joined_data.withColumn(
'etl_requests_usage', lit('DEV')
).withColumn(
'etl_datetime_local', current_date()
).withColumn(
'etl_transformation_name', lit('agg_canvas_logs_user_agent_types')
).withColumn(
'etl_pdi_version', lit(r'Apache Spark')
).withColumn(
'etl_pdi_build_version', lit(r'1.6.1')
).withColumn(
'etl_pdi_hostname', lit(r'N/A')
).withColumn(
'etl_pdi_ipaddress', lit(r'N/A')
).withColumn(
'etl_checksum_md5', lit(r'N/A')
)
作为PS,有没有比我添加列的方式更好的方法?如果需要,甚至可以直接使用SQL表达式:
expr = """
CASE
WHEN user_agent LIKE \'%Android%\' THEN \'mobile\'
WHEN user_agent LIKE \'%Linux%\' THEN \'desktop\'
ELSE \'other_unknown\'
END AS user_agent_type"""
df = sc.parallelize([
(1, "Android"), (2, "Linux"), (3, "Foo")
]).toDF(["id", "user_agent"])
df.selectExpr("*", expr).show()
## +---+----------+---------------+
## | id|user_agent|user_agent_type|
## +---+----------+---------------+
## | 1| Android| mobile|
## | 2| Linux| desktop|
## | 3| Foo| other_unknown|
## +---+----------+---------------+
否则,您可以将其替换为when和like以及other的组合:
您还可以在一次选择中添加多列:
非常令人印象深刻,我忘了我可以直接使用SQL。我不确定Spark SQL与我习惯使用的PostGRESql方言有多相似。HiveQL不是ANSI SQL,但它已经足够接近了。无论何时,只要您使用的不是Postgres特定的扩展,它就可以正常工作。我不会过度使用,但有时它比编写表达式要简洁得多。reduce语句中的类似语句来自哪里?我在pyspark和functools中都找不到文档。@flybonzai这个答案太棒了。如果将其添加到API中,那就太酷了。
expr = """
CASE
WHEN user_agent LIKE \'%Android%\' THEN \'mobile\'
WHEN user_agent LIKE \'%Linux%\' THEN \'desktop\'
ELSE \'other_unknown\'
END AS user_agent_type"""
df = sc.parallelize([
(1, "Android"), (2, "Linux"), (3, "Foo")
]).toDF(["id", "user_agent"])
df.selectExpr("*", expr).show()
## +---+----------+---------------+
## | id|user_agent|user_agent_type|
## +---+----------+---------------+
## | 1| Android| mobile|
## | 2| Linux| desktop|
## | 3| Foo| other_unknown|
## +---+----------+---------------+
from pyspark.sql.functions import col, when
from functools import reduce
c = col("user_agent")
vs = [("Android", "mobile"), ("Linux", "desktop")]
expr = reduce(
lambda acc, kv: when(c.like(kv[0]), kv[1]).otherwise(acc),
vs,
"other_unknown"
).alias("user_agent_type")
df.select("*", expr).show()
## +---+----------+---------------+
## | id|user_agent|user_agent_type|
## +---+----------+---------------+
## | 1| Android| mobile|
## | 2| Linux| desktop|
## | 3| Foo| other_unknown|
## +---+----------+---------------+
exprs = [c.alias(a) for (a, c) in [
('etl_requests_usage', lit('DEV')),
('etl_datetime_local', current_date())]]
df.select("*", *exprs)