Java 如何让ApacheSpark忽略查询中的点？

给定以下JSON文件：

[{"dog*woof":"bad dog 1","dog.woof":"bad dog 32"}]

为什么此Java代码失败：

DataFrame df = sqlContext.read().json("dogfile.json");
df.groupBy("dog.woof").count().show();

但这并不是：

DataFrame df = sqlContext.read().json("dogfile.json");
df.groupBy("dog*woof").count().show();

这是失败的一个片段：

 Exception in thread "main" org.apache.spark.sql.AnalysisException: cannot resolve 'dog.woof' given input columns: [dog*woof, dog.woof];
    at org.apache.spark.sql.catalyst.analysis.package$AnalysisErrorAt.failAnalysis(package.scala:42)
    at org.apache.spark.sql.catalyst.analysis.CheckAnalysis$$anonfun$checkAnalysis$1$$anonfun$apply$2.applyOrElse(CheckAnalysis.scala:60)
    at org.apache.spark.sql.catalyst.analysis.CheckAnalysis$$anonfun$checkAnalysis$1$$anonfun$apply$2.applyOrElse(CheckAnalysis.scala:57)
    at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$transformUp$1.apply(TreeNode.scala:335)
    at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$transformUp$1.apply(TreeNode.scala:335)
    at org.apache.spark.sql.catalyst.trees.CurrentOrigin$.withOrigin(TreeNode.scala:69)
    at org.apache.spark.sql.catalyst.trees.TreeNode.transformUp(TreeNode.scala:334)
...

---

它失败是因为点用于访问

struct

字段的属性。可以使用反勾号转义列名：

val df = sqlContext.read.json(sc.parallelize(Seq(
   """{"dog*woof":"bad dog 1","dog.woof":"bad dog 32"}"""
)))

df.groupBy("`dog.woof`").count.show
// +----------+-----+
// |  dog.woof|count|
// +----------+-----+
// |bad dog 32|    1|
// +----------+-----+

但是，在名称中使用特殊字符并不是一种好的做法，一般情况下都无法使用