ClickHouse's Lazy Materialization: A 1500x Speed Boost
2025-04-22
ClickHouse achieves a 1500x speed improvement using a new optimization called "lazy materialization." This technique delays reading column data until it's actually needed, dramatically reducing unnecessary I/O. The article uses the Amazon customer reviews dataset to illustrate how lazy materialization, combined with other I/O optimizations like columnar storage, sparse primary indexes, and PREWHERE, reduces a query's execution time from 219 seconds to 139 milliseconds. Lazy materialization is particularly effective for Top N queries, providing significant performance gains without altering the SQL.