Data-Engineer-Associate domain - 6% of the exam

Databricks Intelligence Platform

Databricks Intelligence Platform is 6% of the Databricks Certified Data Engineer Associate exam. These are the objectives it covers, each with practice questions, with every answer explained.

Objectives in this domain

Sample question from this domain

Free sampleDatabricks Intelligence Platformmedium

A Delta table sets delta.logRetentionDuration to 30 days and keeps the default file retention for VACUUM. After a routine VACUUM run, an analyst queries the table with VERSION AS OF set to a version that was committed twenty days ago. What is the expected outcome?

VACUUM prod.sales.orders;
SELECT * FROM prod.sales.orders VERSION AS OF 118;
  • AThe query returns the rows as they stood at that version, because the log entry describing the version is retained for the full thirty days.
  • BThe query is rejected before execution, because VERSION AS OF can only address versions committed within the past seven days on any Delta table.
  • CThe query returns an empty result set, because VACUUM rewrites each historical version of the table so that it contains no rows at all.
  • DThe query fails, because VACUUM has removed data files that the twenty-day-old version still references, even though the log entry for that version survives. Correct
Delta Lake time travel needs the data files as well as the log entry, so VACUUM retention limits how far back a query can reach. A Delta table version is a list of data files recorded in the transaction log. Log retention governs how long that list is kept, while VACUUM governs how long the files themselves are kept once no current version references them. When the two settings disagree, the shorter file retention wins in practice, because a version whose files have been deleted cannot be reconstructed and the read fails.

Why A is wrong: This is tempting because the log retention setting really is thirty days, but a log entry only lists the data files a version needs; it does not keep those files alive once VACUUM has removed them.

Why B is wrong: Seven days is the default VACUUM file retention rather than a fixed limit on time travel syntax, so this invents a hard rule that Delta Lake does not enforce on the query itself.

Why C is wrong: VACUUM only deletes files that the current version no longer references and never rewrites historical versions, so an empty result would misrepresent what the command does.

Why D is correct: Correct, because time travel needs both the log entry and the data files it points to, and VACUUM deletes unreferenced files older than the retention threshold regardless of log retention.

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See also the Data-Engineer-Associate cert hub, the study guide, and the cheat sheet.

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