Unlock this content
Enter your email to unlock this content for free
Matviews Expert Advice
Expert advice for working with materialized views in production: only the left table triggers materialized views in joins, always filter joins by the current block to avoid OOM errors, Union ALL is not supported in open-source ClickHouse, cannot over-aggregate (ClickHouse is fast at 10% aggregation ratio), monitor insert latency and timeouts, avoid chains of materialized views, and use proper dev tools that abstract database operations.
Some quick expert advice when working with materialized views in ClickHouse. These tips will help you avoid common pitfalls and build production-ready systems.
Joins in Materialized Views
When you do joins in materialized views, only the left table triggers the materialized view. If you join table_a LEFT JOIN table_b, only inserts into table_a trigger the materialized view. Beware of memory issues especially in joins; if the right table is huge, you need to filter properly to avoid memory problems.
Critical tip for joins:
When joining tables in materialized views, you must filter by something that refers to the current block being inserted. Materialized views only see the current block, so joins must be scoped to that block. Joining huge tables without filtering can cause OOM errors and kill your cluster.