如何在 spark 2.0 中使用 Cassandra Context [英] how to use Cassandra Context in spark 2.0

问题描述

在以前的 Spark 版本(如 1.6.1)中，我正在使用 spark Context 创建 Cassandra Context，

In previous Version of Spark like 1.6.1, i am using creating Cassandra Context using spark Context,

import org.apache.spark.{ Logging, SparkContext, SparkConf }
//config
val conf: org.apache.spark.SparkConf = new SparkConf(true)
.set("spark.cassandra.connection.host", CassandraHost)
.setAppName(getClass.getSimpleName)
 lazy val sc = new SparkContext(conf)
 val cassandraSqlCtx: org.apache.spark.sql.cassandra.CassandraSQLContext = new CassandraSQLContext(sc)
//Query using Cassandra context
  cassandraSqlCtx.sql("select id from table ")

但是在 Spark 2.0 中，Spark Context 被 Spark session 替换，我如何使用 cassandra 上下文?

But In Spark 2.0 , Spark Context is replaced with Spark session, how can i use cassandra context?

推荐答案

简短回答:您没有.它已被弃用和删除.

Short Answer: You don't. It has been deprecated and removed.

长答案:你不想.HiveContext 提供除目录之外的所有内容，并支持更广泛的 SQL(HQL~).在 Spark 2.0 中，这仅意味着您需要使用 createOrReplaceTempView 手动注册 Cassandra 表，直到实现 ExternalCatalogue.

Long Answer: You don't want to. The HiveContext provides everything except for the catalogue and supports a much wider range of SQL(HQL~). In Spark 2.0 this just means you will need to manually register Cassandra tables use createOrReplaceTempView until an ExternalCatalogue is implemented.

在Sql中这看起来像

spark.sql("""CREATE TEMPORARY TABLE words
     |USING org.apache.spark.sql.cassandra
     |OPTIONS (
     |  table "words",
     |  keyspace "test")""".stripMargin)

在原始 DF api 中它看起来像

In the raw DF api it looks like

spark
 .read
 .format("org.apache.spark.sql.cassandra")
 .options(Map("keyspace" -> "test", "table" -> "words"))
 .load
 .createOrReplaceTempView("words")

这两个命令都会为 SQL 查询注册words"表.

Both of these commands will register the table "words" for SQL queries.

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