system.metric_log

Querying in ClickHouse Cloud

The data in this system table is held locally on each node in ClickHouse Cloud. Obtaining a complete view of all data, therefore, requires the clusterAllReplicas function. See here for further details.

Contains history of metrics values from tables system.metrics and system.events, periodically flushed to disk.

Columns:

• hostname (LowCardinality(String)) — Hostname of the server executing the query.
• event_date (Date) — Event date.
• event_time (DateTime) — Event time.
• event_time_microseconds (DateTime64) — Event time with microseconds resolution.

Example

Schema This table can be configured with different schema types using the XML tag <schema_type>. The default schema type is wide, where each metric or profile event is stored as a separate column. This schema is the most performant and efficient for single-column reads.

The transposed schema stores data in a format similar to system.asynchronous_metric_log, where metrics and events are stored as rows. This schema is useful for low-resource setups because it reduces resource consumption during merges.

There is also a compatibility schema, transposed_with_wide_view, which stores actual data in a table with the transposed schema (system.transposed_metric_log) and creates a view on top of it using the wide schema. This view queries the transposed table, making it useful for migrating from the wide schema to the transposed schema.

See also

• metric_log setting — Enabling and disabling the setting.
• system.asynchronous_metrics — Contains periodically calculated metrics.
• system.events — Contains a number of events that occurred.
• system.metrics — Contains instantly calculated metrics.
• Monitoring — Base concepts of ClickHouse monitoring.