What is columnar storage and why is it faster for analytics?

Answer

Columnar storage organizes data on disk by column rather than by row, so all values of a single column are stored together. Analytical queries that scan or aggregate a few columns across millions of rows read only the relevant columns, drastically reducing I/O compared with row storage. Storing similar values together also yields excellent compression, further cutting scan cost. Formats like Apache Parquet and ORC, and warehouses like BigQuery and Redshift, use columnar layouts, which is why they excel at OLAP while row stores remain better for OLTP point lookups and writes.