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50 lines
2.7 KiB
Markdown
50 lines
2.7 KiB
Markdown
---
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slug: /en/operations/system-tables/query_metric_log
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---
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# query_metric_log
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Contains history of memory and metric values from table `system.events` for individual queries, periodically flushed to disk.
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Once a query starts, data is collected at periodic intervals of `query_metric_log_interval` milliseconds (which is set to 1000
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by default). The data is also collected when the query finishes if the query takes longer than `query_metric_log_interval`.
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Columns:
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- `query_id` ([String](../../sql-reference/data-types/string.md)) — ID of the query.
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- `hostname` ([LowCardinality(String)](../../sql-reference/data-types/string.md)) — Hostname of the server executing the query.
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- `event_date` ([Date](../../sql-reference/data-types/date.md)) — Event date.
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- `event_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Event time.
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- `event_time_microseconds` ([DateTime64](../../sql-reference/data-types/datetime64.md)) — Event time with microseconds resolution.
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**Example**
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``` sql
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SELECT * FROM system.query_metric_log LIMIT 1 FORMAT Vertical;
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```
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``` text
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Row 1:
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──────
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query_id: 97c8ba04-b6d4-4bd7-b13e-6201c5c6e49d
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hostname: clickhouse.eu-central1.internal
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event_date: 2020-09-05
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event_time: 2020-09-05 16:22:33
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event_time_microseconds: 2020-09-05 16:22:33.196807
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memory_usage: 313434219
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peak_memory_usage: 598951986
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ProfileEvent_Query: 0
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ProfileEvent_SelectQuery: 0
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ProfileEvent_InsertQuery: 0
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ProfileEvent_FailedQuery: 0
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ProfileEvent_FailedSelectQuery: 0
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...
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```
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**See also**
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- [query_metric_log setting](../../operations/server-configuration-parameters/settings.md#query_metric_log) — Enabling and disabling the setting.
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- [query_metric_log_interval](../../operations/settings/settings.md#query_metric_log_interval)
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- [system.asynchronous_metrics](../../operations/system-tables/asynchronous_metrics.md) — Contains periodically calculated metrics.
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- [system.events](../../operations/system-tables/events.md#system_tables-events) — Contains a number of events that occurred.
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- [system.metrics](../../operations/system-tables/metrics.md) — Contains instantly calculated metrics.
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- [Monitoring](../../operations/monitoring.md) — Base concepts of ClickHouse monitoring.
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