我正在努力展平结构内有结构的 JSON 模式。问题是内部结构名称是动态的,因此我无法使用“.”轻松访问它们。概念
该架构类似于:
root
|-- A: string (nullable = true)
|-- Plugins: struct (nullable = true)
| |-- RfS: struct (nullable = true)
| |-- A
| |-- B
| |-- RtW: struct (nullable = true)
| |-- A
| |-- B
所以 As 和 Bs 是固定的,但每个 JSON 文件都有不同的数字结构和不同的名称 (RfS,RtW) .. 可能是 2 .. 可能是 5 .. 具有我不知道的动态名称。
我怎样才能以动态的方式轻松地扁平化这个结构?
下一个解决方案是使用单个选择和chain https://stackoverflow.com/questions/952914/how-to-make-a-flat-list-out-of-list-of-lists用于展平最终列的函数:
from pyspark.sql.functions import col
from itertools import chain
jsonData = """{
"A" : "some A",
"Plugins": {
"RfS": {
"A" : "RfSA",
"B" : "RfSB"
},
"RtW" : {
"A" : "RtWA",
"B" : "RtWA"
}
}
}"""
df = spark.read.json(sc.parallelize([jsonData]))
no_plug_cols = ["A"] # cols not in Plugins i.e A
plug_df = df.select("A", "Plugins.*")
# plug_df.printSchema()
# root
# |-- A: string (nullable = true)
# |-- RfS: struct (nullable = true)
# | |-- A: string (nullable = true)
# | |-- B: string (nullable = true)
# |-- RtW: struct (nullable = true)
# | |-- A: string (nullable = true)
# | |-- B: string (nullable = true)
# note that we use sets i.e set(plug_df.columns) - set(no_plug_cols) to retrieve cols in Plugins only
icols = [(col(f"{c}.A").alias(f"{c}.A"), col(f"{c}.B").alias(f"{c}.B"))
for c in (set(plug_df.columns) - set(no_plug_cols))]
# we use chain to flatten icols which is a list of tuples
plug_df.select(no_plug_cols + list(chain(*icols))).show()
# +------+-----+-----+-----+-----+
# | A|RfS.A|RfS.B|RtW.A|RtW.B|
# +------+-----+-----+-----+-----+
# |some A| RfSA| RfSB| RtWA| RtWA|
# +------+-----+-----+-----+-----+
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