This is a regular “data quiz”. Follow it on LinkedIn. Test your knowledge or learn something new.
Today Question:
Delta Lake adds to Parquet files:
A) Schema
B) Transactions
C) Metadata
D) All of the above
Correct Answer: D
Explanation
Delta Lake is an open-source storage layer that turns plain Parquet files into a robust transactional data lake with ACID properties. Delta Lake adds four key layers on top of Parquet:
1) SCHEMA — automatic schema validation and enforcement to prevent accidental writes with incorrect structure,
2) TRANSACTIONS — ACID guarantees with atomic writes, consistency checks, isolation, and durability,
3) METADATA — rich metadata including the transaction log (delta log), version history, statistics, partitioning information, and lineage, and
4) advanced features such as time travel, data versioning, VACUUM for cleaning old files, OPTIMIZE for compaction, and Z-ordering for better query performance.
The delta log is a JSON-based log that records all changes to the table, enabling time travel and audit history. These combined features solve traditional data lake problems such as small files, schema drift, failed writes, and unreadable data.