Which feature of Delta Lake allows new fields to be added to existing records retroactively?

Schema evolution is the feature of Delta Lake that allows new fields to be added to existing records retroactively. This capability is crucial in scenarios where data structures change over time; for instance, if you need to accommodate new attributes without having to rewrite or migrate the entire dataset. Schema evolution enables users to seamlessly incorporate these additions, ensuring that the updated schema is reflected across all existing data, which promotes flexibility in data management.

In contrast, time travel features allow users to access historical versions of data to view changes over time, but do not directly facilitate the addition of new fields to existing records. Change Data Capture primarily focuses on capturing and propagating changes in data, like inserts, updates, and deletes, rather than schema modifications. Data compaction, on the other hand, refers to the optimization of storage and performance by consolidating data files but does not play a role in altering or extending the schema itself.

Thus, schema evolution is specifically designed to handle the addition of new fields in existing records, making it the correct answer for this question.