[英]How to split dataframe into multiple dataframes by their column datatypes using SparkSQL?
下面是示例 dataframe,我想根據它們的數據類型將其拆分為多個數據幀或 rdd
ID:Int
Name:String
Joining_Date: Date
我的數據框中有 100 多列,是否有任何內置方法可以實現此邏輯?
據我所知,沒有內置功能可以實現這一點,但是這里有一種方法可以根據列類型將一個 dataframe 分成多個數據幀。
首先讓我們創建一些數據:
from pyspark.sql.functions import col
from pyspark.sql.types import StructType, StructField, StringType, LongType, DateType
df = spark.createDataFrame([
(0, 11, "t1", "s1", "2019-10-01"),
(0, 22, "t2", "s2", "2019-02-11"),
(1, 23, "t3", "s3", "2018-01-10"),
(1, 24, "t4", "s4", "2019-10-01")], ["i1", "i2", "s1", "s2", "date"])
df = df.withColumn("date", col("date").cast("date"))
# df.printSchema()
# root
# |-- i1: long (nullable = true)
# |-- i2: long (nullable = true)
# |-- s1: string (nullable = true)
# |-- s2: string (nullable = true)
# |-- date: date (nullable = true)
然后我們將前面的 dataframe 的列分組到一個字典中,其中鍵是列類型,值是與該類型對應的列的列表:
d = {}
# group cols into a dict by type
for c in df.schema:
key = c.dataType
if not key in d.keys():
d[key] = [c.name]
else:
d[key].append(c.name)
d
# {DateType: ['date'], StringType: ['s1', 's2'], LongType: ['i1', 'i2']}
然后我們遍歷鍵(col 類型)並為字典的每個項目生成模式以及相應的空 dataframe:
type_dfs = {}
# create schema for each type
for k in d.keys():
schema = StructType(
[
StructField(cname , k) for cname in d[k]
])
# finally create an empty df with that schema
type_dfs[str(k)] = spark.createDataFrame(sc.emptyRDD(), schema)
type_dfs
# {'DateType': DataFrame[date: date],
# 'StringType': DataFrame[s1: string, s2: string],
# 'LongType': DataFrame[i1: bigint, i2: bigint]}
最后,我們可以通過訪問 type_dfs 的每一項來使用生成的數據幀:
type_dfs['StringType'].printSchema()
# root
# |-- s1: string (nullable = true)
# |-- s2: string (nullable = true)
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