问题描述
如果我想从case class中创建一个StructType(即一个DataFrame.schema)，是否有一种方法可以在不创建DataFrame的情况下进行呢?我可以轻松做到:
If I wanted to create a StructType (i.e. a DataFrame.schema) out of a case class, is there a way to do it without creating a DataFrame? I can easily do:
case class TestCase(id: Long)
val schema = Seq[TestCase]().toDF.schema
但是当我想要的只是模式时，实际上创建DataFrame似乎有些矫kill过正.
But it seems overkill to actually create a DataFrame when all I want is the schema.
(如果您很好奇，那么问题背后的原因是我正在定义一个UserDefinedAggregateFunction，为此您可以重写几个返回StructTypes的方法，并使用案例类.)
(If you are curious, the reason behind the question is that I am defining a UserDefinedAggregateFunction, and to do so you override a couple of methods that return StructTypes and I use case classes.)
推荐答案
您可以用可以做到:
You can do it the same way SQLContext.createDataFrame does it:
import org.apache.spark.sql.catalyst.ScalaReflection
val schema = ScalaReflection.schemaFor[TestCase].dataType.asInstanceOf[StructType]
这篇关于从案例类生成Spark StructType/Schema的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！