我有一个parquet文件，其中一列是存储json的struct字段。结构如下图所示。
originator: struct (nullable = true)
|-- originatorDetail: struct (nullable = true)
| |-- applicationDeployedId: string (nullable = true)
| |-- applicationDeployedNameVersion: string (nullable = true)
| |-- applicationNameVersion: string (nullable = true)
| |-- cloudHost: string (nullable = true)
| |-- cloudRegion: string (nullable = true)
| |-- cloudStack: string (nullable = true)
| |-- version: string (nullable = true)
|-- Orversion: string (nullable = true)json中只有version字段是必需的，其他字段是非必需的。所以有些记录可能只有2个元素，仍然有效。
假设我想读取cloudhost字段。我可以读作originator.originatordetail.cloudhost。但对于不存在此非必需字段的记录。它将失败，因为元素不在那里。有没有什么方法可以在不使用自定义项的情况下，将这些不需要的值读取为空的记录值。
一些例子
originator": {
"originatorDetail": {
"applicationDeployedId": "PSLV",
"cloudRegion": "Mangal",
"cloudHost": "Petrol",
"applicationNameVersion": "CRDI",
"applicationDeployedNameVersion": "Tuna",
"cloudStack": "DEV",
"version": "1.1.0"
},
Orversion": "version.1"
}
-------------
originator": {
"originatorDetail": {
"version": "1.1.0"
},
Orversion": "version.1"
}所需输出
applicationDeployedId applicationDeployedNameVersion applicationNameVersion cloudHost cloudRegion cloudStack version Orversion
PSLV Tuna CRDI Petrol Mangal DEV 1.1.0 version.1
1.1.0 version.1
1条答案
按热度按时间bzzcjhmw1#
使用
from_json来自spark-2.4的函数+读取Parquet数据，然后使用
from_json通过传递与json列匹配的模式。spark将读取匹配的数据并添加具有空值的非匹配字段。
Example:```df.show(10,False)
+---+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|id |json_data #|
+---+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|1 |{"originator": {"originatorDetail": {"applicationDeployedId": "PSLV","cloudRegion": "Mangal","cloudHost": "Petrol","applicationNameVersion": "CRDI","applicationDeployedNameVersion": "Tuna","cloudStack": "DEV","version": "1.1.0"},"Orversion": "version.1"}}|
|2 |{"originator": { "originatorDetail": { "version": "1.1.0" }, "Orversion": "version.1"}} |
+---+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
schema=StructType([StructField("originator",StructType([StructField("Orversion",StringType(),True),
StructField("originatorDetail",StructType([StructField("applicationDeployedId",StringType(),True),
StructField("applicationDeployedNameVersion",StringType(),True),
StructField("applicationNameVersion",StringType(),True),
StructField("cloudHost",StringType(),True),
StructField("cloudRegion",StringType(),True),
StructField("cloudStack",StringType(),True),
StructField("version",StringType(),True)]),True)]),True)])
from pyspark.sql.functions import *
from pyspark.sql.types import *
then read the json_data column using from_json function
df.withColumn("json_converted",from_json(col("json_data"),schema)).select("id","json_converted").show(10,False)
+---+--------------------------------------------------------+
|id |json_converted |
+---+--------------------------------------------------------+
|1 |version.1, [PSLV, Tuna,, Petrol, Mangal, DEV, 1.1.0]|
|2 |version.1, [,,,,,, 1.1.0] |
+---+--------------------------------------------------------+
df.withColumn("json_converted",from_json(col("json_data"),schema)).select("id","json_converted").printSchema()
root
|-- id: long (nullable = true)
|-- json_converted: struct (nullable = true)
| |-- originator: struct (nullable = true)
| | |-- Orversion: string (nullable = true)
| | |-- originatorDetail: struct (nullable = true)
| | | |-- applicationDeployedId: string (nullable = true)
| | | |-- applicationDeployedNameVersion: string (nullable = true)
| | | |-- applicationNameVersi: string (nullable = true)
| | | |-- cloudHost: string (nullable = true)
| | | |-- cloudRegion: string (nullable = true)
| | | |-- cloudStack: string (nullable = true)
| | | |-- version: string (nullable = true)
even though we don't have all fields from id=2 still we added fields
df.withColumn("json_converted",from_json(col("json_data"),schema)).select("json_converted.originator.originatorDetail.applicationDeployedId").show(10,False)
+---------------------+
|applicationDeployedId|
+---------------------+
|PSLV |
|null |
+---------------------+