Java – Spark SQL DataFrame映射函数不起作用

在Spark SQL中,当我尝试在DataFrame上使用map函数时,我遇到了错误.

DataFrame类型中的方法映射(Function1,ClassTag)不适用于参数(new Function(){})

我也在关注spark 1.3文档. https://spark.apache.org/docs/latest/sql-programming-guide.html#inferring-the-schema-using-reflection有任何解决方案吗？

这是我的测试代码.

   // SQL can be run over RDDs that have been registered as tables.
DataFrame teenagers = sqlContext.sql("SELECT name FROM people WHERE age >= 13 AND age <= 19");

List<String> teenagerNames = teenagers.map(
            new Function<Row, String>() {
          public String call(Row row) {
            return "Name: " + row.getString(0);
          }
        }).collect();

解决方法:

将其更改为：

Java 6& 7

List<String> teenagerNames = teenagers.javaRDD().map(
    new Function<Row, String>() {
    public String call(Row row) {
        return "Name: " + row.getString(0);
    }
}).collect();

Java 8

List<String> t2 = teenagers.javaRDD().map(
    row -> "Name: " + row.getString(0)
).collect();

一旦调用javaRDD(),它就像任何其他RDD映射函数一样工作.

这适用于Spark 1.3.0及更高版本.

标签：map-function,java,apache-spark,sql
来源： https://codeday.me/bug/20191005/1856389.html