Why Spark replaced MapReduce for big data in Apache Spark - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Spark session.

Apache Spark

from pyspark.sql import SparkSession
spark = SparkSession.builder.appName([1]).getOrCreate()

Drag options to blanks, or click blank then click option'

AMyApp

BSparkSession

CappName

D"MyApp"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the app name string.

Passing the class name instead of a string.

The appName method requires a string argument to name the Spark application.

2fill in blank

medium

Complete the code to read a CSV file into a Spark DataFrame.

Apache Spark

df = spark.read.format([1]).option("header", "true").load("data.csv")

Drag options to blanks, or click blank then click option'

Acsv

Bjson

Cparquet

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'json' or 'parquet' format for a CSV file.

Not specifying the format at all.

To read a CSV file, the format must be set to 'csv'.

3fill in blank

hard

Fix the error in the code to cache a DataFrame in Spark.

Apache Spark

df.[1]()

Drag options to blanks, or click blank then click option'

Astore

Bcache

Cpersist

Dsave

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'persist()' without parameters when 'cache()' is intended.

Using 'save()' which writes data to storage.

The correct method to cache a DataFrame in Spark is 'cache()'.

4fill in blank

hard

Fill both blanks to create a DataFrame with only rows where age is greater than 30.

Apache Spark

filtered_df = df.filter(df.[1] [2] 30)

Drag options to blanks, or click blank then click option'

Aage

B>

C<

Dsalary

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong column name like 'salary'.

Using '<' instead of '>'.

To filter rows where age is greater than 30, use df.age > 30.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps words to their lengths if length is greater than 3.

Apache Spark

lengths = { [1]: [2] for [3] in words if len([3]) > 3 }

Drag options to blanks, or click blank then click option'

Aword

Blen(word)

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names.

Not using len(word) for the value.

The comprehension maps each word to its length for words longer than 3 characters.

Practice

1. Why is Apache Spark generally faster than MapReduce for big data processing?

easy

A. Because Spark processes data in memory instead of writing to disk after each step

B. Because Spark uses more disk space for intermediate data

C. Because Spark only supports batch processing

D. Because Spark requires less memory than MapReduce

Solution

1. Step 1: Understand MapReduce data processing

   MapReduce writes intermediate results to disk after each map and reduce step, which slows down processing.

2. Step 2: Understand Spark's in-memory processing

   Spark keeps data in memory during processing, reducing slow disk I/O and speeding up tasks.

3. Final Answer:

   Because Spark processes data in memory instead of writing to disk after each step -> Option A

4. Quick Check:

   In-memory processing = Faster Spark [OK]

Hint: Remember Spark keeps data in RAM, MapReduce uses disk [OK]

Common Mistakes:

• Thinking Spark uses more disk space than MapReduce
• Believing Spark only supports batch processing
• Assuming Spark requires less memory always

2. Which of the following is a correct reason why Spark is easier to program than MapReduce?

easy

A. Spark supports multiple programming languages like Python, Java, and Scala

B. Spark requires writing complex XML configuration files

C. Spark only supports Java programming

D. Spark does not support any APIs

Solution

1. Step 1: Identify Spark's language support

   Spark supports multiple languages such as Python, Java, Scala, and R, making it accessible to many developers.

2. Step 2: Compare with MapReduce programming

   MapReduce programming is mostly Java-based and requires more boilerplate code, making it harder to write.

3. Final Answer:

   Spark supports multiple programming languages like Python, Java, and Scala -> Option A

4. Quick Check:

   Multi-language support = Easier Spark programming [OK]

Hint: Spark supports Python and Scala, MapReduce mostly Java [OK]

Common Mistakes:

• Thinking Spark requires XML configs
• Believing Spark only supports Java
• Assuming Spark has no APIs

3. Consider this Spark code snippet:

val data = spark.sparkContext.parallelize(1 to 5)
val result = data.map(x => x * 2).collect()

What will be the output of result?

medium

A. An error because of syntax

B. [1, 2, 3, 4, 5]

C. [0, 2, 4, 6, 8]

D. [2, 4, 6, 8, 10]

Solution

1. Step 1: Understand the input data

   The data RDD contains numbers from 1 to 5 inclusive.

2. Step 2: Apply the map transformation

   Each element is multiplied by 2, so 1*2=2, 2*2=4, ..., 5*2=10.

3. Final Answer:

   [2, 4, 6, 8, 10] -> Option D

4. Quick Check:

   Multiply each number by 2 = [2,4,6,8,10] [OK]

Hint: Map doubles each number, so output doubles input list [OK]

Common Mistakes:

• Confusing input and output values
• Thinking syntax causes error
• Assuming map adds instead of multiplies

4. This Spark code throws an error:

val data = spark.sparkContext.parallelize(1 to 3)
val result = data.reduce((a, b) => a + b + c)

What is the cause of the error?

medium

A. Reduce function requires three parameters

B. Variable 'c' is not defined in the reduce function

C. parallelize method is incorrect

D. SparkContext is not initialized

Solution

1. Step 1: Analyze the reduce function parameters

   The reduce function takes two parameters, here named 'a' and 'b'.

2. Step 2: Identify the error in the function body

   The function tries to use 'c' which is not defined anywhere, causing a compilation error.

3. Final Answer:

   Variable 'c' is not defined in the reduce function -> Option B

4. Quick Check:

   Undefined variable 'c' causes error [OK]

Hint: Check all variables used inside functions are defined [OK]

Common Mistakes:

• Thinking reduce needs three parameters
• Assuming parallelize is wrong
• Believing SparkContext is uninitialized

5. You want to perform real-time data processing and machine learning on big data. Why would Spark be a better choice than MapReduce?

hard

A. Spark cannot handle machine learning tasks

B. MapReduce supports real-time streaming better than Spark

C. Spark supports in-memory streaming and ML libraries, enabling faster real-time analytics

D. MapReduce processes data only in memory

Solution

1. Step 1: Understand Spark's capabilities

   Spark has built-in modules like Spark Streaming for real-time data and MLlib for machine learning.

2. Step 2: Compare with MapReduce limitations

   MapReduce is batch-oriented and does not support real-time streaming or integrated ML libraries efficiently.

3. Final Answer:

   Spark supports in-memory streaming and ML libraries, enabling faster real-time analytics -> Option C

4. Quick Check:

   Streaming + ML support = Spark advantage [OK]

Hint: Spark = streaming + ML; MapReduce = batch only [OK]

Common Mistakes:

• Believing MapReduce supports real-time streaming
• Thinking Spark cannot do machine learning
• Assuming MapReduce processes data in memory