Data Engineering Associate with Databricks Practice Exam

What is the function of the vacuum command in data management?

1. To permanently delete flagged data

2. To optimize data storage by removing outdated files

3. To backup data tables automatically

4. To restore deleted data files

The correct answer is: To optimize data storage by removing outdated files

The vacuum command is primarily used in data management to optimize data storage by removing outdated files. In systems like Delta Lake, which is built on top of Apache Spark, the vacuum command helps maintain the performance of the data lake. When data is modified or deleted in a Delta table, the old files associated with those changes are not immediately removed but are marked as 'deleted' or 'obsolete.' Over time, if these old files are not cleared out, they can consume significant storage resources and slow down query performance. The vacuum command identifies these obsolete files and purges them based on a defined retention period, which helps reclaim storage space and improve the efficiency of data processing operations. This is particularly important in environments where data is continuously ingested, modified, or deleted. The other choices do not accurately describe the function of the vacuum command. For example, while the vacuum command does deal with removing data, it does not permanently delete flagged data unless the flagged data meets the criteria for being considered obsolete. Additionally, it does not have any functionality related to automated backups or restoring deleted data files, which are separate functions in data management systems.