What is the primary purpose of deletion vectors in Delta Lake?

To automatically cluster data based on query patterns

To encrypt data at rest for security compliance

To mark rows as deleted without rewriting the underlying data files

To compress data files to reduce storage footprint

What is stored in a deletion vector file?

A list of row positions that are marked as deleted in the corresponding data file

A copy of the entire data file with deleted rows removed

The schema of the table and the list of all columns

The full content of the deleted rows

A data engineer is troubleshooting a Delta table with deletion vectors enabled. After many deletes, query performance has degraded significantly. The table is large, and the team cannot afford a full table rewrite. What should the engineer do to improve query performance?

Increase the number of files in the table to spread out the deletion vectors.

Use liquid clustering on the table to reorganize data and remove deletion vectors.

Disable deletion vectors and run VACUUM.

Run OPTIMIZE with the REWRITE DATA option on the table.

What is the relationship between liquid clustering and Z-ordering?

Z-ordering is a newer version of liquid clustering

They are the same feature with different names

Liquid clustering is only for partitioned tables, while Z-ordering is for non-partitioned tables

Liquid clustering is a replacement for Z-ordering that requires less manual maintenance

A team has a Delta table with columns `country`, `region`, and `city`. Queries frequently filter on `country` and `city`. They want to use liquid clustering to improve query performance. Which clustering key configuration should they choose?

Cluster on `country` and `city`.

Partition the table by `city` and cluster on `country`.

DatabricksCertified Data Engineer Professional

Domain 6Objective 2

Understand Delta Optimization Techniques, Such as Deletion Vectors and Liquid Clustering. DATA-ENGINEER-PROFESSIONAL Practice Questions (Page 1)

Part of the Cost & Performance Optimization domain, which accounts for 13% of the DATA-ENGINEER-PROFESSIONAL exam. Databricks does not publish an official question count, but from its 120-minute exam (~50–80 total, ~7–10 in this domain), expect 1–2 from this objective — we provide 29 practice questions to prepare you well beyond it. (estimate)

29questions here

6free pages

9concepts

13%of the exam

Questions 1–5

1foundation · easy
What is the primary purpose of deletion vectors in Delta Lake?
Select an answer first
2foundation · easy
What is stored in a deletion vector file?
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3expert · hard
A data engineer is troubleshooting a Delta table with deletion vectors enabled. After many deletes, query performance has degraded significantly. The table is large, and the team cannot afford a full table rewrite. What should the engineer do to improve query performance?
Select an answer first
4foundation · easy
What is the relationship between liquid clustering and Z-ordering?
Select an answer first
5application · medium
A team has a Delta table with columns `country`, `region`, and `city`. Queries frequently filter on `country` and `city`. They want to use liquid clustering to improve query performance. Which clustering key configuration should they choose?
Select an answer first

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