Which statement about Delta tables and optimization is true?

• A. It sorts data but does not affect file size.
• B. It creates many small Parquet files to increase parallelism.
• C. It does not affect the Delta table's layout on disk.
• D. It sorts data and creates fewer, larger Parquet files.

Answer: (D)

Delta table optimization reorganizes how data is stored to speed up queries. When you run OPTIMIZE (and optionally ZORDER), Delta Lake rewrites small Parquet files into fewer, larger ones and sorts the data within those files to improve data locality. This reduces metadata overhead and the number of files that must be scanned, leading to faster reads, especially for range or join predicates. Therefore, the true statement is that it sorts data and creates fewer, larger Parquet files. The other descriptions don’t fit because optimization does change the on-disk layout by consolidating files and improving data organization, rather than leaving file sizes unchanged or increasing the number of small files.