From Traditional Partitions to Micro-Partitions—How Snowflake and Databend Reduce Data Scanning

A cluster key is neither a B-tree index nor a set of independent access paths for individual columns. It improves physical data locality so that similar key values tend to land in the same or adjacent micro-partitions or blocks. This narrows each physical unit's Min/Max range, reduces overlap, and allows the engine to prune more data before reading it.