Sortkey

A sortkey is a term used in database and data warehouse systems to denote one or more columns whose values determine the physical or logical order of rows. By arranging data according to a sort key, systems can accelerate range scans, skip non-matching blocks, and improve compression, thereby speeding queries that filter or group by the key.

In practice, sort keys appear as properties of a table or index. In columnar data warehouses such as Amazon Redshift, a sort key controls on-disk data ordering; data loaded into a table can be stored in sorted order to optimize query execution. Redshift distinguishes compound sort keys (multiple columns with a fixed priority) and interleaved sort keys (equal weight to each key column, aiding queries on any key).

Usage considerations include choosing sort keys based on prevalent query patterns. A well-chosen sort key improves performance for range and join operations and reduces the need to sort at runtime, but it can slow data loading and updates and may reduce flexibility for queries not aligned with the key.

Related concepts and variants include sort order, index keys, and clustering keys. Some systems offer automatic clustering or maintenance tools that adjust or rebuild sort keys to reflect changing workloads. While the term is most common in data warehousing contexts, the underlying idea—ordering data to optimize access patterns—appears in various database and analytics environments.