SQLContext.gerorCreate is not a value - scala

I am getting error SQLContext.gerorCreate is not a value of object org.apache.spark.SQLContext. This is my code
import org.apache.spark.SparkConf
import org.apache.spark.streaming.StreamingContext
import org.apache.spark.streaming.Seconds
import org.apache.spark.streaming.kafka.KafkaUtils
import org.apache.spark.sql.functions
import org.apache.spark.sql.SQLContext
import org.apache.spark.sql.types
import org.apache.spark.SparkContext
import java.io.Serializable
case class Sensor(id:String,date:String,temp:String,press:String)
object consum {
def main(args: Array[String]) {
val sparkConf = new SparkConf().setAppName("KafkaWordCount").setMaster("local[2]")
val ssc = new StreamingContext(sparkConf, Seconds(2))
val sc=new SparkContext(sparkConf)
val lines = KafkaUtils.createStream(ssc, "localhost:2181", "spark-streaming-consumer-group", Map("hello" -> 5))
def parseSensor(str:String): Sensor={
val p=str.split(",")
Sensor(p(0),p(1),p(2),p(3))
}
val data=lines.map(_._2).map(parseSensor)
val sqlcontext=new SQLContext(sc)
import sqlcontext.implicits._
data.foreachRDD { rdd=>
val sensedata=sqlcontext.getOrCreate(rdd.sparkContext)
}
I have tried with SQLContext.getOrCreate as well but same error.

There is no such getOrCreate function defined for neither SparkContext nor SQLContext.
getOrCreate function is defined for SparkSession instances from which SparkSession instances are created. And we get sparkContext instance or sqlContext instance from the SparkSession instance created using getOrCreate method call.
I hope the explanation is clear.
Updated
The explanation I did above is suitable for higher versions of spark. In the blog as the OP is referencing, the author is using spark 1.6 and the api doc of 1.6.3 clearly states
Get the singleton SQLContext if it exists or create a new one using the given SparkContext

Related

import sqlContext cannot be resolved although defined with SQLContext instance

I followed the solutions in here, however, I am still getting the "cannot resolve symbol SQLContext" error. ".implicits._" cannot be resolved either. What would be the reason for it?
Spark/Scala versions I use:
Scala 2.12.13
Spark 3.0.1 (without bundled Hadoop)
Here is my related code part:
import org.apache.log4j.LogManager
import org.apache.spark.{SparkConf, SparkContext}
object Count {
def main(args: Array[String]) {
...
...
val sc = new SparkContext(conf)
val sqlContext = new SQLContext(sc)
import sqlContext.implicits._
}}
You didn't import SQLContext at all:
import org.apache.spark.sql.SQLContext
You should probably not use SQLContext anymore in the first place though:
As of Spark 2.0, this is replaced by SparkSession. However, we are keeping the class here for backward compatibility.
https://spark.apache.org/docs/latest/api/scala/org/apache/spark/sql/SQLContext.html
See how to use a SparkSession from SparkContext at How to create SparkSession from existing SparkContext and then import sparkSession.implicits._.

Error found when importing spark.implicits

I am using spark 1.4.0
When I tried to import spark.implicits using this command:
import spark.implicits._, this error appear:
<console>:19: error: not found: value spark
import spark.implicits._
^
Can anyone help me to resolve this problem ?
It's because SparkSession is avialable from Spark 2.0 and spark value is an object of type SparkSession in Spark REPL.
In Spark 1.4 use
import sqlContext.implicits._
Value sqlContext is automatically created in Spark REPL for Spark 1.x
To make it complete, first you have to create a sqlContext
import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.sql.SQLContext
val conf = new SparkConf().setMaster("local").setAppName("my app")
val sc = new SparkContext(conf)
val sqlContext = new SQLContext(sc)
import sqlContext.implicits._

Converting error with RDD operation in Scala

I am new to Scala and I ran into the error while doing some practice.
I tried to convert RDD into DataFrame and following is my code.
package com.sclee.examples
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.IntType
import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.sql.Row
import org.apache.spark.sql.types.{LongType, StringType, StructField, StructType};
object App {
def main(args: Array[String]): Unit = {
val conf = new SparkConf().setAppName("examples").setMaster("local")
val sc = new SparkContext(conf)
val sqlContext = new org.apache.spark.sql.SQLContext(sc)
import sqlContext.implicits._
case class Person(name: String, age: Long)
val personRDD = sc.makeRDD(Seq(Person("A",10),Person("B",20)))
val df = personRDD.map({
case Row(val1: String, val2: Long) => Person(val1,val2)
}).toDS()
// val ds = personRDD.toDS()
}
}
I followed the instructions in Spark documentation and also referenced some blogs showing me how to convert rdd into dataframe but the I got the error below.
Error:(20, 27) Unable to find encoder for type stored in a Dataset. Primitive types (Int, String, etc) and Product types (case classes) are supported by importing sqlContext.implicits._ Support for serializing other types will be added in future releases.
val df = personRDD.map({
Although I tried to fix the problem by myself but failed. Any help will be appreciated.
The following code works:
import org.apache.spark.rdd.RDD
import org.apache.spark.sql.SparkSession
case class Person(name: String, age: Long)
object SparkTest {
def main(args: Array[String]): Unit = {
// use the SparkSession of Spark 2
val spark = SparkSession
.builder()
.appName("Spark SQL basic example")
.config("spark.some.config.option", "some-value")
.getOrCreate()
import spark.implicits._
// this your RDD - just a sample how to create an RDD
val personRDD: RDD[Person] = spark.sparkContext.parallelize(Seq(Person("A",10),Person("B",20)))
// the sparksession has a method to convert to an Dataset
val ds = spark.createDataset(personRDD)
println(ds.count())
}
}
I made the following changes:
use SparkSession instead of SparkContext and SqlContext
move Person class out of the App (I'm not sure why I had to do
this)
use createDataset for conversion
However, I guess it's pretty uncommon to do this conversion and you probably want to read your input directly into an Dataset using the read method

Count calls of UDF in Spark

Using Spark 1.6.1 I want to call the number of times a UDF is called. I want to do this because I have a very expensive UDF (~1sec per call) and I suspect the UDF being called more often than the number of records in my dataframe, making my spark job slower than necessary.
Although I could not reproduce this situation, I came up with a simple example showing that the number of calls to the UDF seems to be different (here: less) than the number of rows, how can that be?
import org.apache.spark.sql.SQLContext
import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.sql.functions.udf
object Demo extends App {
val conf = new SparkConf().setMaster("local[4]").setAppName("Demo")
val sc = new SparkContext(conf)
sc.setLogLevel("WARN")
val sqlContext = new SQLContext(sc)
import sqlContext.implicits._
val callCounter = sc.accumulator(0)
val df= sc.parallelize(1 to 10000,numSlices = 100).toDF("value")
println(df.count) // gives 10000
val myudf = udf((d:Int) => {callCounter.add(1);d})
val res = df.withColumn("result",myudf($"value")).cache
println(res.select($"result").collect().size) // gives 10000
println(callCounter.value) // gives 9941
}
If using an accumulator is not the right way to call the counts of the UDF, how else could I do it?
Note: In my actual Spark-Job, get a call-count which is about 1.7 times higher than the actual number of records.
Spark applications should define a main() method instead of extending scala.App. Subclasses of scala.App may not work correctly.
import org.apache.spark.sql.SQLContext
import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.sql.functions.udf
object Demo extends App {
def main(args: Array[String]): Unit = {
val conf = new SparkConf().setAppName("Simple Application").setMaster("local[4]")
val sc = new SparkContext(conf)
// [...]
}
}
This should solve your problem.

More than one spark context error

I have this spark code below:
import org.apache.hadoop.hbase.client._
import org.apache.hadoop.hbase.{ HBaseConfiguration, HTableDescriptor }
import org.apache.hadoop.hbase.mapreduce.TableInputFormat
import org.apache.hadoop.hbase.io.ImmutableBytesWritable
import org.apache.hadoop.hbase.util.Bytes
import kafka.serializer.StringDecoder
import org.apache.spark._
import org.apache.spark.SparkContext._
import org.apache.spark.streaming._
import org.apache.spark.streaming.kafka._
object Hbase {
def main(args: Array[String]) {
val sparkConf = new SparkConf().setAppName("Spark-Hbase").setMaster("local[2]")
val sc = new SparkContext(sparkConf)
...
val ssc = new StreamingContext(sparkConf, Seconds(3))
val kafkaBrokers = Map("metadata.broker.list" -> "localhost:9092")
val topics = List("test").toSet
val lines = KafkaUtils.createDirectStream[String, String, StringDecoder, StringDecoder](ssc, kafkaBrokers, topics)
}
}
Now the error I am getting is:
Only one SparkContext may be running in this JVM (see SPARK-2243). To ignore this error, set spark.driver.allowMultipleContexts = true.
Is there anything wrong with my code above? I do not see where I am creating the context again...
These are the two SparkContext you're creating. This is not allowed.
val sc = new SparkContext(sparkConf)
val ssc = new StreamingContext(sparkConf, Seconds(3))
You should create the streaming context from the original context.
val ssc = new StreamingContext(sc, Seconds(3))
you are initializing two spark context in the same JVM i.e. (sparkContext and streamingContext). That's why you are getting this exception. you can set spark.driver.allowMultipleContexts = true in config. Although, multiple Spark contexts is discouraged. You can get unexpected results.