Creating Empty Dataframe in Apache Spark

In Apache Spark, a DataFrame is a distributed collection of data organized into named columns. It is a key component of Spark SQL and provides a rich set of operations to process and manipulate data. In this article, we will discuss how to create an empty DataFrame in Spark using Scala.

Table of Contents

Step 1: Import Required Packages

To create a DataFrame in Spark using Scala, we first need to import the necessary packages. The following packages need to be imported:

import org.apache.spark.sql.{DataFrame, SparkSession}
import org.apache.spark.sql.types.{StructType, StructField, StringType, IntegerType}

Step 2: Create a SparkSession

The next step is to create a SparkSession, which is the entry point to Spark SQL. We can create a SparkSession as follows:

val spark = SparkSession.builder()
  .appName("CreateEmptyDataFrame")
  .master("local[*]")
  .getOrCreate()

In the above code, we create a SparkSession with the name “CreateEmptyDataFrame” and set the master URL to “local[*]” to run Spark in local mode.

Step 3: Define the Schema

Before we can create an empty DataFrame, we need to define the schema of the DataFrame. The schema defines the columns of the DataFrame and their data types. We can define a schema as follows:

val schema = StructType(
  Array(
    StructField("name", StringType, nullable = false),
    StructField("age", IntegerType, nullable = false)
  )
)

In the above code, we define a schema with two columns: “name” of type StringType and “age” of type IntegerType. We set the nullable flag to false to indicate that these columns cannot have null values.

Step 4: Create an Empty DataFrame

Once we have defined the schema, we can create an empty DataFrame using the createDataFrame method of the SparkSession object. We can create an empty DataFrame as follows:

val emptyDF = spark.createDataFrame(spark.sparkContext.emptyRDD[Row], schema)

In the above code, we create an empty RDD using the emptyRDD method of the SparkContext object and pass it to the createDataFrame method along with the schema. The createDataFrame method returns an empty DataFrame with the specified schema.

Step 5: Display the Empty DataFrame

Finally, we can display the empty DataFrame using the show method. We can display an empty DataFrame as follows:

emptyDF.show()

In the above code, we call the show method on the empty DataFrame to display its contents. Since the DataFrame is empty, the show method displays an empty table.