v.25.4New Feature

Support a background refresh

Official CH changelog text
Support for a background refresh in readonly MergeTree tables which allows querying updateable tables with an infinite amount of distributed readers (ClickHouse-native data lake). #76467 (Alexey Milovidov).
Introduces support for background refresh in readonly MergeTree tables, enabling updateable tables to be queried concurrently by an unlimited number of distributed readers, effectively supporting a ClickHouse-native data lake architecture.

Why it matters

This feature addresses the challenge of efficiently handling multiple distributed readers querying updateable tables without locking or performance degradation. It provides a scalable solution for use cases requiring a large number of concurrent readers on readonly tables that can still be updated in the background.

How to use it

Users can enable background refresh on readonly MergeTree tables to allow continuous background updates while serving a large number of distributed reads. This setup facilitates querying updateable tables seamlessly in distributed environments, typical of data lake architectures.

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