v.20.3Improvement
Enable system.metric_log by Default for ProfileEvents and CurrentMetrics
Enable system.metric_log by default. It will contain rows with values of ProfileEvents, CurrentMetrics collected with "collect_interval_milliseconds" interval (one second by default). The table is very small (usually in order of megabytes) and collecting this data by default is reasonable. #9225 (alexey-milovidov)Why it matters
This feature automatically gathers detailed system metrics such as ProfileEvents and CurrentMetrics at regular intervals (default one second), providing immediate insight into ClickHouse performance without manual setup. It solves the problem of monitoring overhead and simplifies performance diagnostics by keeping a compact, continuously updated log.How to use it
Thesystem.metric_log table is enabled by default and collects metric data at an interval specified by the collect_interval_milliseconds setting (default 1000 ms). Users can query this table directly to analyze recent metrics without additional configuration.