获取scala中Object/Case类的大小

Question

import org.apache.spark.util.SizeEstimator
case class event(imei: String, date: String)
val check = event(imei, date)
      println("size is event obj " + SizeEstimator.estimate(check))
      println("size is single charct " + SizeEstimator.estimate("a"))
      println("size is imei " + SizeEstimator.estimate(imei))

size is event obj 520
size is single 48
size is imei 72

Answer 1

scala> val char:java.lang.Character = 'a'
char: Character = a

scala> SizeEstimator.estimate(char)
res18: Long = 16

scala> SizeEstimator.estimate("A")
res19: Long = 48

如果您想要实际的Java堆大小，就必须用Java类型专门声明它们，否则仅仅使用单引号是行不通的。

scala> SizeEstimator.estimate('A')
<console>:27: error: type mismatch;
 found   : Char('A')
 required: AnyRef
Note: an implicit exists from scala.Char => java.lang.Character, but
methods inherited from Object are rendered ambiguous.  This is to avoid
a blanket implicit which would convert any scala.Char to any AnyRef.
You may wish to use a type ascription: `x: java.lang.Character`.
              SizeEstimator.estimate('A')

下面是字符串大小的计算公式-

最小字符串内存使用量（字节）=8*(int)(((no chars)*2)+45)/8)

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