When working with ClickHouse®, writing a query is usually straightforward. Writing an efficient query, however, requires understanding how ClickHouse reads and filters data.
Many users assume that adding a simple WHERE clause automatically results in fast query performance. While filtering is certainly important, not all filters are equally effective.
The difference between a query that scans millions of rows and one that scans only a fraction of them often comes down to how the filtering conditions align with the table design.
In this article, we'll explore how filtering works in ClickHouse®, common mistakes to avoid, and practical best practices for improving query performance.
Why Filtering Matters
