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

Explanation

The key here is to understand that columns that are passed to DataFrame.drop() are ignored if they do not exist in the DataFrame. So, passing column name associateId to transactionsDf.drop()

does not have any effect.

Passing a list to transactionsDf.drop() is not valid. The documentation (link below) shows the call structure as DataFrame.drop(*cols). The * means that all arguments that are passed to

DataFrame.drop() are read as columns. However, since a list of columns, for example ["predError", "productId", "associateId"] is not a column, Spark will run into an error.

More info: pyspark.sql.DataFrame.drop — PySpark 3.1.1 documentation

Static notebook | Dynamic notebook: See test 1, QUESTION NO: 50 (Databricks import instructions)

Explanation

transactionsDf.repartition(transactionsDf.rdd.getNumPartitions()+2)

Correct. The repartition operator is the correct one for increasing the number of partitions. calling getNumPartitions() on DataFrame.rdd returns the current number of partitions.

transactionsDf.coalesce(10)

No, after this command transactionsDf will continue to only have 8 partitions. This is because coalesce() can only decreast the amount of partitions, but not increase it.

transactionsDf.repartition(transactionsDf.getNumPartitions()+2)

Incorrect, there is no getNumPartitions() method for the DataFrame class.

transactionsDf.coalesce(transactionsDf.getNumPartitions()+2)

Wrong, coalesce() can only be used for reducing the number of partitions and there is no getNumPartitions() method for the DataFrame class.

transactionsDf.repartition(transactionsDf._partitions+2)

No, DataFrame has no _partitions attribute. You can find out the current number of partitions of a DataFrame with the DataFrame.rdd.getNumPartitions() method.

More info: pyspark.sql.DataFrame.repartition — PySpark 3.1.2 documentation, pyspark.RDD.getNumPartitions — PySpark 3.1.2 documentation

Static notebook | Dynamic notebook: See test 3, QUESTION NO: 23 (Databricks import instructions)

Explanation

Correct code block: transactionsDf.drop("productId", "f")

This QUESTION NO: requires a lot of thinking to get right. For solving it, you may take advantage of the digital notepad that is provided to you during the test. You have probably seen that the code

block

includes multiple errors. In the test, you are usually confronted with a code block that only contains a single error. However, since you are practicing here, this challenging multi-error QUESTION

NO: will

make it easier for you to deal with single-error questions in the real exam.

The select operator should be replaced by a drop operator, the column names should be listed directly as arguments to the operator and not as a list, and all column names should be expressed as

strings without being wrapped in a col() operator.

Correct! Here, you need to figure out the many, many things that are wrong with the initial code block. While the QUESTION NO: can be solved by using a select statement, a drop statement, given

the

answer options, is the correct one. Then, you can read in the documentation that drop does not take a list as an argument, but just the column names that should be dropped. Finally, the column

names should be expressed as strings and not as Python variable names as in the original code block.

The column names should be listed directly as arguments to the operator and not as a list.

Incorrect. While this is a good first step and part of the correct solution (see above), this modification is insufficient to solve the question.

The column names should be listed directly as arguments to the operator and not as a list and following the pattern of how column names are expressed in the code block, columns productId and f

should be replaced by transactionId, predError, value and storeId.

Wrong. If you use the same pattern as in the original code block (col(productId), col(f)), you are still making a mistake. col(productId) will trigger Python to search for the content of a variable named

productId instead of telling Spark to use the column productId - for that, you need to express it as a string.

The select operator should be replaced by a drop operator, the column names should be listed directly as arguments to the operator and not as a list, and all col() operators should be removed.

No. This still leaves you with Python trying to interpret the column names as Python variables (see above).

The select operator should be replaced by a drop operator.

Wrong, this is not enough to solve the question. If you do this, you will still face problems since you are passing a Python list to drop and the column names are still interpreted as Python variables

(see above).

More info: pyspark.sql.DataFrame.drop — PySpark 3.1.2 documentation

Static notebook | Dynamic notebook: See test 3, QUESTION NO: 30 (Databricks import instructions)