Databricks Exam Databricks-Certified-Associate-Developer-for-Apache-Spark-3.0 Topic 1 Question 47 Discussion

Correct code block:

schema = StructType([

StructField('itemId', IntegerType(), True),

StructField('attributes', ArrayType(StringType(), True), True),

StructField('supplier', StringType(), True)

])

spark.read.options(modifiedBefore='2029-03-20T05:44:46').schema(schema).parquet(filePath)

This Question: is more difficult than what you would encounter in the exam. In the exam, for this Question: type, only one error needs to be identified and not 'one or multiple' as in the

question.

Columns in the schema definition use the wrong object type, the modification date threshold is specified incorrectly, and Spark cannot identify the file format.

Correct! Columns in the schema definition should use the StructField type. Building a schema from pyspark.sql.types, as here using classes like StructType and StructField, is one of multiple ways

of expressing a schema in Spark. A StructType always contains a list of StructFields (see documentation linked below). So, nesting StructType and StructType as shown in the Question: is

wrong.

The modification date threshold should be specified by a keyword argument like options(modifiedBefore='2029-03-20T05:44:46') and not two consecutive non-keyword arguments as in the original

code block (see documentation linked below).

Spark cannot identify the file format correctly, because either it has to be specified by using the DataFrameReader.format(), as an argument to DataFrameReader.load(), or directly by calling, for

example, DataFrameReader.parquet().

Columns in the schema are unable to handle empty values and the modification date threshold is specified incorrectly.

No. If StructField would be used for the columns instead of StructType (see above), the third argument specified whether the column is nullable. The original schema shows that columns should be

nullable and this is specified correctly by the third argument being True in the schema in the code block.

It is correct, however, that the modification date threshold is specified incorrectly (see above).

The attributes array is specified incorrectly, Spark cannot identify the file format, and the syntax of the call to Spark's DataFrameReader is incorrect.

Wrong. The attributes array is specified correctly, following the syntax for ArrayType (see linked documentation below). That Spark cannot identify the file format is correct, see correct answer

above. In addition, the DataFrameReader is called correctly through the SparkSession spark.

Columns in the schema definition use the wrong object type and the syntax of the call to Spark's DataFrameReader is incorrect.

Incorrect, the object types in the schema definition are correct and syntax of the call to Spark's DataFrameReader is correct.

The data type of the schema is incompatible with the schema() operator and the modification date threshold is specified incorrectly.

False. The data type of the schema is StructType and an accepted data type for the DataFrameReader.schema() method. It is correct however that the modification date threshold is specified

incorrectly (see correct answer above).