pyspark 数据类型及转换

 

spark 有哪些数据类型 https://spark.apache.org/docs/latest/sql-reference.html

 

Spark 数据类型

Data Types

Spark SQL and DataFrames support the following data types:

• Numeric types
  • ByteType: Represents 1-byte signed integer numbers. The range of numbers is from -128 to 127.
  • ShortType: Represents 2-byte signed integer numbers. The range of numbers is from -32768 to 32767.
  • IntegerType: Represents 4-byte signed integer numbers. The range of numbers is from -2147483648 to 2147483647.
  • LongType: Represents 8-byte signed integer numbers. The range of numbers is from -9223372036854775808 to 9223372036854775807.
  • FloatType: Represents 4-byte single-precision floating point numbers.
  • DoubleType: Represents 8-byte double-precision floating point numbers.
  • DecimalType: Represents arbitrary-precision signed decimal numbers. Backed internally by java.math.BigDecimal. A BigDecimal consists of an arbitrary precision integer unscaled value and a 32-bit integer scale.
• String type
  • StringType: Represents character string values.
• Binary type
  • BinaryType: Represents byte sequence values.
• Boolean type
  • BooleanType: Represents boolean values.
• Datetime type
  • TimestampType: Represents values comprising values of fields year, month, day, hour, minute, and second.
  • DateType: Represents values comprising values of fields year, month, day.
• Complex types
  • ArrayType(elementType, containsNull): Represents values comprising a sequence of elements with the type of elementType. containsNull is used to indicate if elements in a ArrayType value can have null values.
  • MapType(keyType, valueType, valueContainsNull): Represents values comprising a set of key-value pairs. The data type of keys are described by keyType and the data type of values are described by valueType. For a MapType value, keys are not allowed to have null values. valueContainsNull is used to indicate if values of a MapType value can have null values.
  • StructType(fields): Represents values with the structure described by a sequence of StructFields (fields).
    • StructField(name, dataType, nullable): Represents a field in a StructType. The name of a field is indicated by name. The data type of a field is indicated by dataType. nullable is used to indicate if values of this fields can have null values.

对应的pyspark 数据类型在这里 pyspark.sql.types

 

一些常见的转化场景：

1. Converts a date/timestamp/string to a value of string, 转成的string 的格式用第二个参数指定

df.withColumn('test', F.date_format(col('Last_Update'),"yyyy/MM/dd")).show()

 

 

 

2. 转成 string后，可以 cast 成你想要的类型，比如下面的 date 型

df = df.withColumn('date', F.date_format(col('Last_Update'),"yyyy-MM-dd").alias('ts').cast("date"))

 

 

 

 

3. 把 timestamp 秒数（从1970年开始）转成日期格式 string

 

4. unix_timestamp 把 日期 String 转换成 timestamp 秒数，是上面操作的反操作

　　

 

 　　因为unix_timestamp 不考虑 ms ，如果一定要考虑ms可以用下面的方法

df1 = df.withColumn("unix_timestamp",F.unix_timestamp(df.TIME,'dd-MMM-yyyy HH:mm:ss.SSS z') + F.substring(df.TIME,-7,3).cast('float')/1000)

 

 

5. timestamp 秒数转换成 timestamp type, 可以用 F.to_timestamp

　　

 

 6. 从timestamp 或者 string 日期类型提取 时间，日期等信息

　　

 

 

 

Ref:

https://stackoverflow.com/questions/54337991/pyspark-from-unixtime-unix-timestamp-does-not-convert-to-timestamp