Experimental ClickHouse ® : Projections

ClickHouse® is known for its fast release cycle, introducing major updates around once a month, which allows for rapid innovation but can complicate the implementation of large features. To manage this, ClickHouse® often introduces new features as experimental, allowing them to be tested and refined before possibly becoming stable or being discarded. One such experimental feature is projections, introduced in version 21.6, which function similarly to materialized views but are automatically utilized by the database depending on the query. Projections offer efficiency by reducing disk usage significantly, though they require duplicating storage. They differ from Skipping Indexes, which are smaller and more limited but also automatically applied to queries. In comparison, materialized views are a stable feature that can be used with any table engine and allow for complex data enrichment, though they may complicate query writing and error recovery. Projections handle errors silently and are generated in the background, offering a less disruptive alternative when dealing with query failures.