上一篇说到，在Spark 2.x当中，实际上SQLContext和HiveContext是过时的，相反是采用SparkSession对象的sql函数来操作SQL语句的。使用这个函数执行SQL语句前需要先调用DataFrame的createOrReplaceTempView注册一个临时表，所以关键是先要将RDD转换成DataFrame。实际上，在Spark中实际声明了
type DataFrame = Dataset[Row]
所以，DataFrame是Dataset[Row]的别名。RDD是提供面向低层次的API，而DataFrame/Dataset提供面向高层次的API（适合于SQL等面向结构化数据的场合）。
下面提供一些Spark SQL程序的例子。
例子一：SparkSQLExam.scala
package bruce.bigdata.spark.example import org.apache.spark.sql.Row
import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.types._ object SparkSQLExam { case class offices(office:Int,city:String,region:String,mgr:Int,target:Double,sales:Double) def main(args: Array[String]) { val spark = SparkSession
.builder
.appName("SparkSQLExam")
.getOrCreate() runSparkSQLExam1(spark)
runSparkSQLExam2(spark) spark.stop() } private def runSparkSQLExam1(spark: SparkSession): Unit = { import spark.implicits._ val rddOffices=spark.sparkContext.textFile("/user/hive/warehouse/orderdb.db/offices/offices.txt").map(_.split("\t")).map(p=>offices(p(0).trim.toInt,p(1),p(2),p(3).trim.toInt,p(4).trim.toDouble,p(5).trim.toDouble))
val officesDataFrame = spark.createDataFrame(rddOffices) officesDataFrame.createOrReplaceTempView("offices")
spark.sql("select city from offices where region='Eastern'").map(t=>"City: " + t(0)).collect.foreach(println) } private def runSparkSQLExam2(spark: SparkSession): Unit = { import spark.implicits._
import org.apache.spark.sql._
import org.apache.spark.sql.types._ val schema = new StructType(Array(StructField("office", IntegerType, false), StructField("city", StringType, false), StructField("region", StringType, false), StructField("mgr", IntegerType, true), StructField("target", DoubleType, true), StructField("sales", DoubleType, false)))
val rowRDD = spark.sparkContext.textFile("/user/hive/warehouse/orderdb.db/offices/offices.txt").map(_.split("\t")).map(p => Row(p(0).trim.toInt,p(1),p(2),p(3).trim.toInt,p(4).trim.toDouble,p(5).trim.toDouble))
val dataFrame = spark.createDataFrame(rowRDD, schema) dataFrame.createOrReplaceTempView("offices2")
spark.sql("select city from offices2 where region='Western'").map(t=>"City: " + t(0)).collect.foreach(println) } }
使用下面的命令进行编译：
[root@BruceCentOS4 scala]# scalac SparkSQLExam.scala
在编译之前，需要在CLASSPATH中增加路径：
export CLASSPATH=$CLASSPATH:$SPARK_HOME/jars/*:$(/opt/hadoop/bin/hadoop classpath)
然后打包成jar文件：
[root@BruceCentOS4 scala]# jar -cvf spark_exam_scala.jar bruce
然后通过spark-submit提交程序到yarn集群执行，为了方便从客户端查看结果，这里采用yarn cient模式运行。
[root@BruceCentOS4 scala]# $SPARK_HOME/bin/spark-submit --class bruce.bigdata.spark.example.SparkSQLExam --master yarn --deploy-mode client spark_exam_scala.jar
运行结果截图：
例子二：SparkSQLExam.scala（需要启动hive metastore）
package bruce.bigdata.spark.example
import org.apache.spark.sql.{SaveMode, SparkSession}
object SparkHiveExam {
def main(args: Array[String]) {
val spark = SparkSession
.builder()
.appName("Spark Hive Exam")
.config("spark.sql.warehouse.dir", "/user/hive/warehouse")
.enableHiveSupport()
.getOrCreate()
import spark.implicits._
//使用hql查看hive数据
spark.sql("show databases").collect.foreach(println)
spark.sql("use orderdb")
spark.sql("show tables").collect.foreach(println)
spark.sql("select city from offices where region='Eastern'").map(t=>"City: " + t(0)).collect.foreach(println)
//将hql查询出的数据保存到另外一张新建的hive表
//找出订单金额超过1万美元的产品
spark.sql("""create table products_high_sales(mfr_id string,product_id string,description string)
ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t' LINES TERMINATED BY '\n' STORED AS TEXTFILE""")
spark.sql("""select mfr_id,product_id,description
from products a inner join orders b
on a.mfr_id=b.mfr and a.product_id=b.product
where b.amount>10000""").write.mode(SaveMode.Overwrite).saveAsTable("products_high_sales")
//将HDFS文件数据导入到hive表中
spark.sql("""CREATE TABLE IF NOT EXISTS offices2 (office int,city string,region string,mgr int,target double,sales double )
ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t' LINES TERMINATED BY '\n' STORED AS TEXTFILE""")
spark.sql("LOAD DATA INPATH '/user/hive/warehouse/orderdb.db/offices/offices.txt' INTO TABLE offices2")
spark.stop()
}
}
使用下面的命令进行编译：
[root@BruceCentOS4 scala]# scalac SparkHiveExam.scala
使用下面的命令打包：
[root@BruceCentOS4 scala]# jar -cvf spark_exam_scala.jar bruce
使用下面的命令运行：
[root@BruceCentOS4 scala]# $SPARK_HOME/bin/spark-submit --class bruce.bigdata.spark.example.SparkHiveExam --master yarn --deploy-mode client spark_exam_scala.jar
程序运行结果：
另外上述程序运行后，hive中多了2张表：
例子三：spark_sql_exam.py
from __future__ import print_function from pyspark.sql import SparkSession
from pyspark.sql.types import * if __name__ == "__main__":
spark = SparkSession \
.builder \
.appName("Python Spark SQL exam") \
.config("spark.some.config.option", "some-value") \
.getOrCreate() schema = StructType([StructField("office", IntegerType(), False), StructField("city", StringType(), False),
StructField("region", StringType(), False), StructField("mgr", IntegerType(), True),
StructField("Target", DoubleType(), True), StructField("sales", DoubleType(), False)]) rowRDD = spark.sparkContext.textFile("/user/hive/warehouse/orderdb.db/offices/offices.txt").map(lambda p: p.split("\t")) \
.map(lambda p: (int(p[0].strip()), p[1], p[2], int(p[3].strip()), float(p[4].strip()), float(p[5].strip()))) dataFrame = spark.createDataFrame(rowRDD, schema)
dataFrame.createOrReplaceTempView("offices")
spark.sql("select city from offices where region='Eastern'").show() spark.stop()
执行命令运行程序：
[root@BruceCentOS4 spark]# $SPARK_HOME/bin/spark-submit --master yarn --deploy-mode client spark_sql_exam.py
程序运行结果：
例子四：JavaSparkSQLExam.java
package bruce.bigdata.spark.example; import java.util.ArrayList;
import java.util.List; import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.function.Function;
import org.apache.spark.api.java.function.MapFunction;
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.RowFactory;
import org.apache.spark.sql.SparkSession;
import org.apache.spark.sql.types.DataTypes;
import org.apache.spark.sql.types.StructField;
import org.apache.spark.sql.types.StructType;
import org.apache.spark.sql.AnalysisException; public class JavaSparkSQLExam {
public static void main(String[] args) throws AnalysisException {
SparkSession spark = SparkSession
.builder()
.appName("Java Spark SQL exam")
.config("spark.some.config.option", "some-value")
.getOrCreate(); List<StructField> fields = new ArrayList<>();
fields.add(DataTypes.createStructField("office", DataTypes.IntegerType, false));
fields.add(DataTypes.createStructField("city", DataTypes.StringType, false));
fields.add(DataTypes.createStructField("region", DataTypes.StringType, false));
fields.add(DataTypes.createStructField("mgr", DataTypes.IntegerType, true));
fields.add(DataTypes.createStructField("target", DataTypes.DoubleType, true));
fields.add(DataTypes.createStructField("sales", DataTypes.DoubleType, false)); StructType schema = DataTypes.createStructType(fields); JavaRDD<String> officesRDD = spark.sparkContext()
.textFile("/user/hive/warehouse/orderdb.db/offices/offices.txt", 1)
.toJavaRDD(); JavaRDD<Row> rowRDD = officesRDD.map((Function<String, Row>) record -> {
String[] attributes = record.split("\t");
return RowFactory.create(Integer.valueOf(attributes[0].trim()), attributes[1], attributes[2], Integer.valueOf(attributes[3].trim()), Double.valueOf(attributes[4].trim()), Double.valueOf(attributes[5].trim()));
}); Dataset<Row> dataFrame = spark.createDataFrame(rowRDD, schema); dataFrame.createOrReplaceTempView("offices");
Dataset<Row> results = spark.sql("select city from offices where region='Eastern'");
results.collectAsList().forEach(r -> System.out.println(r)); spark.stop();
}
}
编译打包后通过如下命令执行：
[root@BruceCentOS4 spark]# $SPARK_HOME/bin/spark-submit --class bruce.bigdata.spark.example.JavaSparkSQLExam --master yarn --deploy-mode client spark_exam_java.jar
运行结果：
上面是一些关于Spark SQL程序的一些例子，分别采用了Scala/Python/Java来编写的。另外除了这三种语言，Spark还支持R语言编写程序，因为我自己也不熟悉，就不举例了。不管用什么语言，其实API都是基本一致的，主要是采用DataFrame和Dataset的高层次API来调用和执行SQL。使用这些API，可以轻松的将结构化数据转化成SQL来操作，同时也能够方便的操作Hive中的数据。