ClickHouse/docs/en/operations/system-tables/query_metric_log.md

slug
/en/operations/system-tables/query_metric_log

query_metric_log

Contains history of memory and metric values from table system.events for individual queries, periodically flushed to disk.

Once a query starts, data is collected at periodic intervals of query_metric_log_interval milliseconds (which is set to 1000 by default). The data is also collected when the query finishes if the query takes longer than query_metric_log_interval.

Columns:

• query_id (String) — ID of the query.
• 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

SELECT * FROM system.query_metric_log LIMIT 1 FORMAT Vertical;

Row 1:
──────
query_id:                                                        97c8ba04-b6d4-4bd7-b13e-6201c5c6e49d
hostname:                                                        clickhouse.eu-central1.internal
event_date:                                                      2020-09-05
event_time:                                                      2020-09-05 16:22:33
event_time_microseconds:                                         2020-09-05 16:22:33.196807
memory_usage:                                                    313434219
peak_memory_usage:                                               598951986
ProfileEvent_Query:                                              0
ProfileEvent_SelectQuery:                                        0
ProfileEvent_InsertQuery:                                        0
ProfileEvent_FailedQuery:                                        0
ProfileEvent_FailedSelectQuery:                                  0
...

See also

• query_metric_log setting — Enabling and disabling the setting.
• query_metric_log_interval
• 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.