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# 系统。trace_log {#system_tables-trace_log}
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包含采样查询探查器收集的堆栈跟踪。
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ClickHouse创建此表时 [trace_log ](../../operations/server-configuration-parameters/settings.md#server_configuration_parameters-trace_log ) 服务器配置部分被设置。 也是 [query_profiler_real_time_period_ns ](../../operations/settings/settings.md#query_profiler_real_time_period_ns ) 和 [query_profiler_cpu_time_period_ns ](../../operations/settings/settings.md#query_profiler_cpu_time_period_ns ) 应设置设置。
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要分析日志，请使用 `addressToLine` , `addressToSymbol` 和 `demangle` 内省功能。
列:
- `event_date` ([日期](../../sql-reference/data-types/date.md)) — Date of sampling moment.
- `event_time` ([日期时间](../../sql-reference/data-types/datetime.md)) — Timestamp of the sampling moment.
- `timestamp_ns` ([UInt64](../../sql-reference/data-types/int-uint.md)) — Timestamp of the sampling moment in nanoseconds.
- `revision` ([UInt32](../../sql-reference/data-types/int-uint.md)) — ClickHouse server build revision.
通过以下方式连接到服务器 `clickhouse-client` ，你看到的字符串类似于 `Connected to ClickHouse server version 19.18.1 revision 54429.` . 该字段包含 `revision` ，但不是 `version` 的服务器。
- `timer_type` ([枚举8](../../sql-reference/data-types/enum.md)) — Timer type:
- `Real` 表示挂钟时间。
- `CPU` 表示CPU时间。
- `thread_number` ([UInt32](../../sql-reference/data-types/int-uint.md)) — Thread identifier.
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- `query_id` ([字符串](../../sql-reference/data-types/string.md)) — Query identifier that can be used to get details about a query that was running from the [query_log ](#system_tables-query_log ) 系统表.
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- `trace` ([数组(UInt64)](../../sql-reference/data-types/array.md)) — Stack trace at the moment of sampling. Each element is a virtual memory address inside ClickHouse server process.
**示例**
``` sql
SELECT * FROM system.trace_log LIMIT 1 \G
```
``` text
Row 1:
──────
event_date: 2019-11-15
event_time: 2019-11-15 15:09:38
revision: 54428
timer_type: Real
thread_number: 48
query_id: acc4d61f-5bd1-4a3e-bc91-2180be37c915
trace: [94222141367858,94222152240175,94222152325351,94222152329944,94222152330796,94222151449980,94222144088167,94222151682763,94222144088167,94222151682763,94222144088167,94222144058283,94222144059248,94222091840750,94222091842302,94222091831228,94222189631488,140509950166747,140509942945935]
```
