在星火使用窗口函数

本文介绍了在星火使用窗口函数的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我想在星火数据帧使用ROWNUMBER。我的查询是否按预期工作在星火外壳。但是，当我在Eclipse中把它们写出来，编译一个罐子，我面临的一个错误

I am trying to use rowNumber in Spark data frames. My queries are working as expected in Spark shell. But when i write them out in eclipse and compile a jar, i am facing an error

 16/03/23 05:52:43 ERROR ApplicationMaster: User class threw exception:org.apache.spark.sql.AnalysisException: Could not resolve window function 'row_number'. Note that, using window functions currently requires a HiveContext;
org.apache.spark.sql.AnalysisException: Could not resolve window function 'row_number'. Note that, using window functions currently requires a HiveContext;

我的查询

import org.apache.spark.sql.functions.{rowNumber, max, broadcast}
import org.apache.spark.sql.expressions.Window
val w = Window.partitionBy($"id").orderBy($"value".desc)

val dfTop = df.withColumn("rn", rowNumber.over(w)).where($"rn" <= 3).drop("rn")

在运行中火花壳查询我不使用HiveContext。不知道为什么，当我运行同一个jar文件它返回一个错误。而且我在星火1.6.0运行脚本是否有帮助。有没有人遇到类似的问题？

I am not using HiveContext while running the queries in spark shell. Not sure why it is returning an error when i run the same as a jar file. And also I am running the scripts on Spark 1.6.0 if that helps. Did anyone face similar issue?

推荐答案

我已经之前回答了.

You can read further about the difference between SQLContextand HiveContext here.

SparkSQL具有SQLContext和HiveContext。 HiveContext是一个超集SQLContext的。星火社区建议使用HiveContext。你可以看到，当您运行火花壳，这就是交互式驱动器的应用，它会自动创建定义为SC和定义为一个sqlContext一个HiveContext SparkContext。该HiveContext允许你执行的SQL查询以及蜂巢命令。

SparkSQL has a SQLContext and a HiveContext. HiveContext is a super set of the SQLContext. The Spark community suggest using the HiveContext. You can see that when you run spark-shell, which is your interactive driver application, it automatically creates a SparkContext defined as sc and a HiveContext defined as sqlContext. The HiveContext allows you to execute SQL queries as well as Hive commands.

您可以尝试检查你的火花外壳里面：

Welcome to
      ____              __
     / __/__  ___ _____/ /__
    _\ \/ _ \/ _ `/ __/  '_/
   /___/ .__/\_,_/_/ /_/\_\   version 1.6.0
      /_/

Using Scala version 2.10.5 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_74)

scala> sqlContext.isInstanceOf[org.apache.spark.sql.hive.HiveContext]
res0: Boolean = true

scala> sqlContext.isInstanceOf[org.apache.spark.sql.SQLContext]
res1: Boolean = true

scala> sqlContext.getClass.getName
res2: String = org.apache.spark.sql.hive.HiveContext

通过继承， HiveContext 实际上是一个 SQLContext 是的，但事实并非如此周围的其他方法。您可以检查来源$ C $ C 如果你知道更多位数的如何做 HiveContext 从 SQLContext 。

By inheritance, HiveContext is actually an SQLContext, but it's not true the other way around. You can check the source code if you are more intersted in knowing how does HiveContext inherits from SQLContext.

                        这篇关于在星火使用窗口函数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！