Explain columnar storage of data compared to relational storage. Is columnar storage more similar to key‑value storage?

Relational databases store data in tables with rows and columns, where each row represents a record and each column a field. Queries often involve scanning entire rows or performing joins, which can be I/O intensive.

Columnar storage, on the other hand, stores each column in a separate file or block. This layout is ideal for analytical queries that read only a few columns from many rows. It enables better compression, as values in a column are more homogeneous, and allows the engine to skip irrelevant data.

Columnar storage is not the same as key‑value storage. Key‑value stores map a unique key to a value and are optimized for simple lookups, whereas columnar databases maintain structured schemas, support complex queries, and provide ACID properties. Columnar databases can be seen as a specialized form of relational storage optimized for read‑heavy analytical workloads, whereas key‑value stores are best for high‑throughput, low‑latency key‑based access.