spark SQL学习（认识spark SQL）

时间 2019-12-18

标签 spark sql 学习认识栏目 Spark 繁體版

原文原文链接

spark SQL初步认识

spark SQL是spark的一个模块，主要用于进行结构化数据的处理。它提供的最核心的编程抽象就是DataFrame。html

DataFrame：它能够根据不少源进行构建，包括：结构化的数据文件，hive中的表，外部的关系型数据库，以及RDDjava

建立DataFrame

数据文件students.jsonsql

{"id":1, "name":"leo", "age":18}
{"id":2, "name":"jack", "age":19}
{"id":3, "name":"marry", "age":17}

spark-shell里建立DataFrameshell

//将文件上传到hdfs目录下
hadoop@master:~/wujiadong$ hadoop fs -put students.json /student/2016113012/spark
//启动spark shell
hadoop@slave01:~$ spark-shell
//导入SQLContext
scala> import org.apache.spark.sql.SQLContext
import org.apache.spark.sql.SQLContext
//声明一个SQLContext的对象，以便对数据进行操做
scala> val sql = new SQLContext(sc)
warning: there was one deprecation warning; re-run with -deprecation for details
sql: org.apache.spark.sql.SQLContext = org.apache.spark.sql.SQLContext@27acd9a7
//读取数据
scala> val students = sql.read.json("hdfs://master:9000/student/2016113012/spark/students.json")
students: org.apache.spark.sql.DataFrame = [age: bigint, id: bigint ... 1 more field]
//显示数据
scala> students.show
+---+---+-----+
|age| id| name|
+---+---+-----+
| 18|  1|  leo|
| 19|  2| jack|
| 17|  3|marry|
+---+---+-----+

DataFrame经常使用操做

scala> students.show
+---+---+-----+
|age| id| name|
+---+---+-----+
| 18|  1|  leo|
| 19|  2| jack|
| 17|  3|marry|
+---+---+-----+

scala> students.printSchema
root
 |-- age: long (nullable = true)
 |-- id: long (nullable = true)
 |-- name: string (nullable = true)
 
 
scala> students.select("name").show
+-----+
| name|
+-----+
|  leo|
| jack|
|marry|
+-----+ 

scala> students.select(students("name"),students("age")+1).show
+-----+---------+
| name|(age + 1)|
+-----+---------+
|  leo|       19|
| jack|       20|
|marry|       18|
+-----+---------+

scala> students.filter(students("age")>18).show
+---+---+----+
|age| id|name|
+---+---+----+
| 19|  2|jack|
+---+---+----+


scala> students.groupBy("age").count().show
+---+-----+                                                                     
|age|count|
+---+-----+
| 19|    1|
| 17|    1|
| 18|    1|
+---+-----+

两种方式将RDD转换成DataFrame

1）基于反射方式

package wujiadong_sparkSQL

import org.apache.spark.sql.SQLContext
import org.apache.spark.{SparkConf, SparkContext}

/**
  * Created by Administrator on 2017/3/5.
  */
object RDDDataFrameReflection {
  def main(args: Array[String]): Unit = {
    val conf = new SparkConf().setAppName("rdddatafromareflection")
    val sc = new SparkContext(conf)
    val sqlContext = new SQLContext(sc)
    val fileRDD = sc.textFile("hdfs://master:9000/student/2016113012/data/students.txt")
    val lineRDD = fileRDD.map(line => line.split(","))
    //将RDD和case class关联
    val studentsRDD = lineRDD.map(x => Students(x(0).toInt,x(1),x(2).toInt))
    //在scala中使用反射方式，进行rdd到dataframe的转换，须要手动导入一个隐式转换
    import sqlContext.implicits._
    val studentsDF = studentsRDD.toDF()
    //注册表
    studentsDF.registerTempTable("t_students")
    val df = sqlContext.sql("select * from t_students")
    df.rdd.foreach(row => println(row(0)+","+row(1)+","+row(2)))
    df.rdd.saveAsTextFile("hdfs://master:9000/student/2016113012/data/out")


  }

}
//放到外面
case class Students(id:Int,name:String,age:Int)

运行结果数据库

hadoop@master:~/wujiadong$ spark-submit --class wujiadong_sparkSQL.RDDDataFrameReflection  --executor-memory 500m --total-executor-cores 2 /home/hadoop/wujiadong/wujiadong.spark.jar
17/03/05 22:46:45 WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
17/03/05 22:46:48 INFO Slf4jLogger: Slf4jLogger started
17/03/05 22:46:48 INFO Remoting: Starting remoting
17/03/05 22:46:49 INFO Remoting: Remoting started; listening on addresses :[akka.tcp://sparkDriver@192.168.1.131:34921]
17/03/05 22:46:49 WARN Utils: Service 'SparkUI' could not bind on port 4040. Attempting port 4041.
17/03/05 22:46:51 WARN MetricsSystem: Using default name DAGScheduler for source because spark.app.id is not set.
17/03/05 22:47:00 INFO FileInputFormat: Total input paths to process : 1
17/03/05 22:47:07 INFO deprecation: mapred.tip.id is deprecated. Instead, use mapreduce.task.id
17/03/05 22:47:07 INFO deprecation: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
17/03/05 22:47:07 INFO deprecation: mapred.task.is.map is deprecated. Instead, use mapreduce.task.ismap
17/03/05 22:47:07 INFO deprecation: mapred.task.partition is deprecated. Instead, use mapreduce.task.partition
17/03/05 22:47:07 INFO deprecation: mapred.job.id is deprecated. Instead, use mapreduce.job.id
1,leo,17
2,marry,17
3,jack,18
4,tom,19
17/03/05 22:47:10 INFO FileOutputCommitter: Saved output of task 'attempt_201703052247_0001_m_000000_1' to hdfs://master:9000/student/2016113012/data/out/_temporary/0/task_201703052247_0001_m_000000

2）编程接口方式

package wujiadong_sparkSQL


import org.apache.spark.sql.types._
import org.apache.spark.sql.{Row, SQLContext}
import org.apache.spark.{SparkConf, SparkContext}

/**
  * Created by Administrator on 2017/3/5.
  */
object RDDDataFrameBianchen {
  def main(args: Array[String]): Unit = {
    val conf = new SparkConf().setAppName("RDDDataFrameBianchen")
    val sc = new SparkContext(conf)
    val sqlContext = new SQLContext(sc)
    //指定地址建立rdd
    val studentsRDD = sc.textFile("hdfs://master:9000/student/2016113012/data/students.txt").map(_.split(","))
    //将rdd映射到rowRDD
    val RowRDD = studentsRDD.map(x => Row(x(0).toInt,x(1),x(2).toInt))
    //以编程方式动态构造元素据
    val schema = StructType(
      List(
        StructField("id",IntegerType,true),
        StructField("name",StringType,true),
        StructField("age",IntegerType,true)
      )
    )
    //将schema信息映射到rowRDD
    val studentsDF = sqlContext.createDataFrame(RowRDD,schema)
    //注册表
    studentsDF.registerTempTable("t_students")
    val df = sqlContext.sql("select * from t_students order by age")
    df.rdd.collect().foreach(row => println(row))
  }

}

运行结果apache

hadoop@master:~/wujiadong$ spark-submit --class wujiadong_sparkSQL.RDDDataFrameBianchen --executor-memory 500m --total-executor-cores 2 /home/hadoop/wujiadong/wujiadong.spark.jar
17/03/06 11:07:25 WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
17/03/06 11:07:27 INFO Slf4jLogger: Slf4jLogger started
17/03/06 11:07:27 INFO Remoting: Starting remoting
17/03/06 11:07:28 INFO Remoting: Remoting started; listening on addresses :[akka.tcp://sparkDriver@192.168.1.131:49756]
17/03/06 11:07:32 WARN MetricsSystem: Using default name DAGScheduler for source because spark.app.id is not set.
17/03/06 11:07:38 INFO FileInputFormat: Total input paths to process : 1
17/03/06 11:07:44 INFO deprecation: mapred.tip.id is deprecated. Instead, use mapreduce.task.id
17/03/06 11:07:44 INFO deprecation: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
17/03/06 11:07:44 INFO deprecation: mapred.task.is.map is deprecated. Instead, use mapreduce.task.ismap
17/03/06 11:07:44 INFO deprecation: mapred.task.partition is deprecated. Instead, use mapreduce.task.partition
17/03/06 11:07:44 INFO deprecation: mapred.job.id is deprecated. Instead, use mapreduce.job.id
[1,leo,17]                                                                      
[2,marry,17]
[3,jack,18]
[4,tom,19]
17/03/06 11:07:47 INFO RemoteActorRefProvider$RemotingTerminator: Shutting down remote daemon.
17/03/06 11:07:47 INFO RemoteActorRefProvider$RemotingTerminator: Remote daemon shut down; proceeding with flushing remote transports.
17/03/06 11:07:47 INFO RemoteActorRefProvider$RemotingTerminator: Remoting shut down.

DataFrame与RDD

1）在spark中，DataFrame是一种以RDD为基础的分布式数据集，相似于传统数据库中的二维表格编程

2）DataFrame与RDD的主要区别就是，前者带有schema元信息，即DataFrame所表示的二维表数据集的每一列都带有名称和类型json

参考资料
http://9269309.blog.51cto.com/9259309/1851673app

参考资料
http://blog.csdn.net/ronaldo4511/article/details/53406069tcp

参考资料 http://spark.apache.org/docs/latest/sql-programming-guide.html#overview