Certified Data Engineer Professional Exam

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Question 107

Which statement describes Delta Lake optimized writes?

Before a Jobs cluster terminates, OPTIMIZE is executed on all tables modified during the most recent job.

An asynchronous job runs after the write completes to detect if files could be further compacted; if yes, an OPTIMIZE job is executed toward a default of 1 GB.

Data is queued in a messaging bus instead of committing data directly to memory; all data is committed from the messaging bus in one batch once the job is complete.

Optimized writes use logical partitions instead of directory partitions; because partition boundaries are only represented in metadata, fewer small files are written.

A shuffle occurs prior to writing to try to group similar data together resulting in fewer files instead of each executor writing multiple files based on directory partitions.

Correct Answer: E

Optimized writes in Delta Lake involve a shuffle operation prior to writing the data. This shuffle groups similar data together, which results in fewer files being written instead of having each executor write multiple small files based on directory partitions. This process aims to improve the efficiency of file management and subsequent reads, although it may increase write latency due to the shuffle.

Discussion

alexvnoOption: E

Optimized writes are most effective for partitioned tables, as they reduce the number of small files written to each partition. Writing fewer large files is more efficient than writing many small files, but you might still see an increase in write latency because data is shuffled before being writte

lexaneonOption: E

https://docs.databricks.com/en/delta/tune-file-size.html#optimized-writes

vctrhugoOption: E

Optimized writes improve file size as data is written and benefit subsequent reads on the table. Optimized writes are most effective for partitioned tables, as they reduce the number of small files written to each partition. Writing fewer large files is more efficient than writing many small files, but you might still see an increase in write latency because data is shuffled before being written. https://learn.microsoft.com/en-us/azure/databricks/delta/tune-file-size#--optimized-writes-for-delta-lake-on-azure-databricks