Databricks-Certified-Associate-Developer-for-Apache-Spark-3.0 Exam Dumps : Databricks Certified Associate Developer for Apache Spark 3.0 Exam

Explanation

Caching means storing a copy of a partition on an executor, so it can be accessed quicker by subsequent operations, instead of having to be recalculated. cache() is a lazily-evaluated method of the

DataFrame. Since count() is an action (while filter() is not), it triggers the caching process.

More info: pyspark.sql.DataFrame.cache — PySpark 3.1.2 documentation, Learning Spark, 2nd Edition, Chapter 7

Static notebook | Dynamic notebook: See test 2, QUESTION NO: 20 (Databricks import instructions)

Explanation

The output is the typical output of a DataFrame.printSchema() call. The DataFrame's RDD representation does not have a printSchema or formatSchema method (find available methods in the RDD

documentation linked below). The output of print(transactionsDf.schema) is this: StructType(List(StructField(transactionId,IntegerType,true),StructField(predError,IntegerType,true),StructField

(value,IntegerType,true),StructField(storeId,IntegerType,true),StructField(productId,IntegerType,true),StructField(f,IntegerType,true))). It includes the same information as the nicely formatted original

output, but is not nicely formatted itself. Lastly, the DataFrame's schema attribute does not have a print() method.

More info:

- pyspark.RDD: pyspark.RDD — PySpark 3.1.2 documentation

- DataFrame.printSchema(): pyspark.sql.DataFrame.printSchema — PySpark 3.1.2 documentation

Static notebook | Dynamic notebook: See test 2, QUESTION NO: 52 (Databricks import instructions)

While only one of these code blocks works, the DataFrame API is pretty flexible when it comes to accepting columns into the pow() method. The following code blocks would also work:

transactionsDf.withColumn("predErrorSquared", pow("predError", 2))

transactionsDf.withColumn("predErrorSquared", pow("predError", lit(2)))

Static notebook | Dynamic notebook: See test 1, QUESTION NO: 26 (Databricks import instructions) ,