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Exam Certified Data Engineer Professional topic 1 question 134 discussion

Actual exam question from Databricks's Certified Data Engineer Professional
Question #: 134
Topic #: 1
[All Certified Data Engineer Professional Questions]

A Delta lake table with CDF enabled table in the Lakehouse named customer_churn_params is used in churn prediction by the machine learning team. The table contains information about customers derived from a number of upstream sources. Currently, the data engineering team populates this table nightly by overwriting the table with the current valid values derived from upstream data sources.

The churn prediction model used by the ML team is fairly stable in production. The team is only interested in making predictions on records that have changed in the past 24 hours.

Which approach would simplify the identification of these changed records?

  • A. Apply the churn model to all rows in the customer_churn_params table, but implement logic to perform an upsert into the predictions table that ignores rows where predictions have not changed.
  • B. Convert the batch job to a Structured Streaming job using the complete output mode; configure a Structured Streaming job to read from the customer_churn_params table and incrementally predict against the churn model.
  • C. Replace the current overwrite logic with a merge statement to modify only those records that have changed; write logic to make predictions on the changed records identified by the change data feed.
  • D. Modify the overwrite logic to include a field populated by calling spark.sql.functions.current_timestamp() as data are being written; use this field to identify records written on a particular date.
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Suggested Answer: C 🗳️
by m79590530 at Oct. 20, 2024, 10:43 a.m.

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m79590530
1 month ago
Selected Answer: C
Why use overwrite for a table that has CDF enabled? Best is to modify it in a SCD Type 1 style by using UPSERTs via the MERGE INTO logic and then/also use its CDF system fields as the means to filter which records are current and which not by selecting only the records that have 'insert' or 'update_postimage' in their _change_type CDF system column.
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