Answer-first summary for fast verification
Answer: 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 128 MB.
Delta Lake Auto Compaction is a feature that automatically compacts small files into larger ones after a write operation to improve read performance. It operates asynchronously, checking for files that can be compacted and then executing an OPTIMIZE job to merge them. The default target file size for this compaction is 128 MB, which is different from the standalone OPTIMIZE command's default of 1 GB. This distinction is crucial for understanding how Auto Compaction works within Delta Lake.
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What is the correct description of Delta Lake Auto Compaction?
A
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.
B
Before a Jobs cluster terminates, OPTIMIZE is executed on all tables modified during the most recent job.
C
Optimized writes use logical partitions instead of directory partitions; because partition boundaries are only represented in metadata, fewer small files are written.
D
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.
E
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 128 MB.