v.25.6Improvement

Better introspection of in-memory caches

Official CH changelog text
Better introspection of in-memory caches (expose information about caches in system.metrics over incomplete system.asynchronouse_metrics). Add in-memory caches size (in bytes) into dashboard.html. VectorSimilarityIndexCacheSize/IcebergMetadataFilesCacheSize has been renamed to VectorSimilarityIndexCacheBytes/IcebergMetadataFilesCacheBytes. #81023 (Azat Khuzhin).
Enhanced introspection of ClickHouse in-memory caches by exposing detailed cache information in system.metrics and adding in-memory cache sizes (in bytes) to the dashboard.html interface. Cache size metric names have been updated for clarity.

Why it matters

This feature improves observability and monitoring of in-memory caches in ClickHouse. By moving cache metrics from the limited system.asynchronous_metrics to the more comprehensive system.metrics system and displaying cache sizes in the dashboard, users gain better insight into cache usage and memory consumption, enabling more effective performance tuning and troubleshooting.

How to use it

Users can access detailed cache metrics directly via queries to the system.metrics table and view cache sizes visually in the ClickHouse dashboard.html. Note that some metric names have been renamed from VectorSimilarityIndexCacheSize and IcebergMetadataFilesCacheSize to VectorSimilarityIndexCacheBytes and IcebergMetadataFilesCacheBytes, so updated metric names should be used in monitoring queries.

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