Spark RDD vs DataFrame vs Dataset

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  • Post category:Apache Spark
  • Post last modified:November 21, 2023
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In this article, Let us discuss the similarities and differences of Spark RDD vs DataFrame vs Datasets. In Spark Scala, RDDs, DataFrames, and Datasets are three important abstractions that allow developers to work with structured data in a distributed computing environment. While RDDs, DataFrames, and Datasets provide a way to represent structured data, they differ in several ways. In this article, we shall discuss Spark RDDs, DataFrames, and Datasets and compare one with the other.

1. Spark RDD

In Apache Spark, RDD (Resilient Distributed Datasets) is a fundamental data structure that represents a collection of elements, partitioned across the nodes of a cluster. RDDs can be created from various data sources, including Hadoop Distributed File System (HDFS), local file system, and data stored in a relational database.

Here is an example of how to create an RDD in Scala:


//Imports
import org.apache.spark.{SparkConf, SparkContext}

//Spark Session
val conf = new SparkConf().setAppName("RDDExample")
                    .setMaster("local")
val sc = new SparkContext(conf)

//Create RDD
val rdd = sc.parallelize(Seq(1, 2, 3, 4, 5))

In the above example, we first create a SparkConf object and set the application name and master URL, which means the Spark job will be executed locally on a single machine. We then create a SparkContext object using the SparkConf object. Finally, we create an RDD by calling the parallelize method on the SparkContext object and passing it in a sequence of integers.

2. Spark DataFrame

In Spark Scala, a DataFrame is a distributed collection of data organized into named columns similar to an SQL table.

  • It is similar to a table in a relational database or a spreadsheet in that it has a schema, which defines the types and names of its columns, and each row represents a single record or observation.
  • DataFrames in Spark Scala can be created from a variety of sources, such as RDDs, structured data files (e.g., CSV, JSON, Parquet), Hive tables, or external databases
  • Once created, DataFrames support a wide range of operations and transformations, such as filtering, aggregating, joining, and grouping data.
  • One of the key benefits of using DataFrames in Spark Scala is their ability to leverage Spark’s distributed computing capabilities to process large amounts of data quickly and efficiently.

Example of how to create and work with a Spark Scala DataFrame:


import org.apache.spark.sql.SparkSession

// create a SparkSession
val spark = SparkSession.builder()
  .appName("example")
  .master("local[*]")
  .getOrCreate()

// create a DataFrame from a sequence of tuples
val data = Seq(("John", 25), ("Jane", 30), ("Bob", 45))
val df = spark.createDataFrame(data).toDF("name", "age")

// display the DataFrame
df.show()

//Result
+----+---+
|name|age|
+----+---+
|John| 25|
|Jane| 30|
| Bob| 45|
+----+---+

Overall, DataFrames in Spark provides a powerful and flexible way to work with structured data in a distributed computing environment.

3. Spark Dataset

A Dataset is a distributed collection of data that provides the benefits of strong typing, compile-time type safety, and object-oriented programming. It is essentially a strongly-typed version of a DataFrame, where each row of the Dataset is an object of a specific type, defined by a case class or a Java class.

  • Datasets in Spark Scala can be created from a variety of sources, such as RDDs, DataFrames, structured data files (e.g., CSV, JSON, Parquet), Hive tables, or external databases.
  • One of the key benefits of using Datasets in Spark Scala is their ability to provide compile-time type safety and object-oriented programming, which can help catch errors at compile time rather than runtime. This can help improve code quality and reduce the likelihood of errors.

Here is an example of how to create and work with a Spark Scala Dataset:


import org.apache.spark.sql.{SparkSession, Encoders}

// create a case class to define the schema of the Dataset
case class Person(name: String, age: Int)

// create a SparkSession
val spark = SparkSession.builder()
  .appName("example")
  .master("local[*]")
  .getOrCreate()

// create a Dataset from a sequence of case class objects
val data = Seq(Person("John", 25), Person("Jane", 30), Person("Bob", 45))
val ds = spark.createDataset(data)(Encoders.product[Person])

// display the Dataset
ds.show()

//Result
+----+---+
|name|age|
+----+---+
|John| 25|
|Jane| 30|
| Bob| 45|
+----+---+

Overall, Datasets in Spark Scala provide a powerful and flexible way to work with typed data in a distributed computing environment.

4. RDD vs DataFrame vs Dataset in Apache Spark

RDDs, DataFrames, and Datasets are all useful abstractions in Apache Spark, each with its own advantages and use cases. Let us now learn the feature-wise difference between Spark RDD vs DataFrame vs DataSet API:

Spark DataFrame vs Dataset
Spark DataFrame vs Dataset
ContextRDDDataFrameDataset
InteroperabilityCan be easily converted to DataFrames and vice versa using the toDF() and rdd() methods.Can be easily converted to RDDs and Datasets using the rdd() and as[] methods respectively.Can be easily converted to DataFrames using the toDF() method, and to RDDs using the rdd() method.
Type safetyNot type-safeDataFrames are not type-safe, When we are trying to access the column which does not exist in the table in such case Dataframe APIs does not support compile-time error. It detects attribute errors only at runtimeDatasets are type-safe, Datasets provide compile-time type checking, which helps catch errors early in the development process. DataFrames are schema-based, meaning that the structure of the data is defined at runtime and is not checked until runtime.
PerformanceLow-level API with more control over the data, but lower-level optimizations compared to DataFrames and Datasets.Optimized for performance, with high-level API, Catalyst optimizer, and code generation.Datasets are faster than DataFrames because they use JVM bytecode generation to perform operations on data. This means that Datasets can take advantage of the JVM’s optimization capabilities, such as just-in-time (JIT) compilation, to speed up processing.
Memory ManagementProvide full control over memory management, as they can be cached in memory or disk as per the user’s choice.Have more optimized memory management, with a Spark SQL optimizer that helps to reduce memory usage.support most of the available dataTypes
SerializationWhenever Spark needs to distribute the data within the cluster or write the data to disk, it does so use Java serialization. The overhead of serializing individual Java and Scala objects is expensive and requires sending both data and structure between nodes.DataFrames use a generic encoder that can handle any object type.Datasets are serialized using specialized encoders that are optimized for performance.
APIsProvide a low-level API that requires more code to perform transformations and actions on dataProvide a high-level API that makes it easier to perform transformations and actions on data.Datasets provide a richer set of APIs. Datasets support both functional and object-oriented programming paradigms and provide a more expressive API for working with data
Schema enforcementDo not have an explicit schema, and are often used for unstructured data.DataFrames enforce schema at runtime. Have an explicit schema that describes the data and its types.Datasets enforce schema at compile time. With Datasets, errors in data types or structures are caught earlier in the development cycle. Have an explicit schema that describes the data and its types, and is strongly typed.
Programming Language SupportRDD APIs are available in Java, Scala, Python, and R languages. Hence, this feature provides flexibility to the developers.Available In 4 languages like Java, Python, Scala, and R.Only available in Scala and Java.
OptimizationNo inbuilt optimization engine is available in RDD.It uses a catalyst optimizer for optimization.It includes the concept of a Dataframe Catalyst optimizer for optimizing query plans.
Data typesSuitable for structured and semi-structured data processing with a higher level of abstraction.DataFrames supports most of the available dataTypesDatasets support all of the same data types as DataFrames, but they also support user-defined types. Datasets are more flexible when it comes to working with complex data types.
Use CasesSuitable for low-level data processing and batch jobs that require fine-grained control over dataSuitable for structured and semi-structured data processing with a higher-level of abstraction.Suitable for high-performance batch and stream processing with strong typing and functional programming.
RDD vs DataFrame vs Dataset

4. Conclusion

In conclusion, Spark RDDs, DataFrames, and Datasets are all useful abstractions in Apache Spark, each with its own advantages and use cases. RDDs are the most basic and low-level API, providing more control over the data but with lower-level optimizations. DataFrames provide a higher-level API that is optimized for performance and easier to work with for structured data. Datasets are similar to DataFrames in performance but with stronger typing and code generation, making them a good choice for high-performance batch and stream processing with strong typing.

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rimmalapudi

Data Engineer. I write about BigData Architecture, tools and techniques that are used to build Bigdata pipelines and other generic blogs.

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  1. pradipjagtap

    Thank you for sharing!