mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-23 16:12:01 +00:00
59 lines
4.2 KiB
Markdown
59 lines
4.2 KiB
Markdown
---
|
|
slug: /en/operations/system-tables/trace_log
|
|
---
|
|
# trace_log
|
|
|
|
Contains stack traces collected by the sampling query profiler.
|
|
|
|
ClickHouse creates this table when the [trace_log](../../operations/server-configuration-parameters/settings.md#server_configuration_parameters-trace_log) server configuration section is set. Also see settings: [query_profiler_real_time_period_ns](../../operations/settings/settings.md#query_profiler_real_time_period_ns), [query_profiler_cpu_time_period_ns](../../operations/settings/settings.md#query_profiler_cpu_time_period_ns), [memory_profiler_step](../../operations/settings/settings.md#memory_profiler_step),
|
|
[memory_profiler_sample_probability](../../operations/settings/settings.md#memory_profiler_sample_probability), [trace_profile_events](../../operations/settings/settings.md#trace_profile_events).
|
|
|
|
To analyze logs, use the `addressToLine`, `addressToLineWithInlines`, `addressToSymbol` and `demangle` introspection functions.
|
|
|
|
Columns:
|
|
|
|
- `hostname` ([LowCardinality(String)](../../sql-reference/data-types/string.md)) — Hostname of the server executing the query.
|
|
- `event_date` ([Date](../../sql-reference/data-types/date.md)) — Date of sampling moment.
|
|
- `event_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Timestamp of the sampling moment.
|
|
- `event_time_microseconds` ([DateTime64](../../sql-reference/data-types/datetime64.md)) — Timestamp of the sampling moment with microseconds precision.
|
|
- `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.
|
|
|
|
When connecting to the server by `clickhouse-client`, you see the string similar to `Connected to ClickHouse server version 19.18.1.`. This field contains the `revision`, but not the `version` of a server.
|
|
|
|
- `trace_type` ([Enum8](../../sql-reference/data-types/enum.md)) — Trace type:
|
|
- `Real` represents collecting stack traces by wall-clock time.
|
|
- `CPU` represents collecting stack traces by CPU time.
|
|
- `Memory` represents collecting allocations and deallocations when memory allocation exceeds the subsequent watermark.
|
|
- `MemorySample` represents collecting random allocations and deallocations.
|
|
- `MemoryPeak` represents collecting updates of peak memory usage.
|
|
- `ProfileEvent` represents collecting of increments of profile events.
|
|
- `thread_id` ([UInt64](../../sql-reference/data-types/int-uint.md)) — Thread identifier.
|
|
- `query_id` ([String](../../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) system table.
|
|
- `trace` ([Array(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.
|
|
- `size` ([Int64](../../sql-reference/data-types/int-uint.md)) - For trace types `Memory`, `MemorySample` or `MemoryPeak` is the amount of memory allocated, for other trace types is 0.
|
|
- `event` ([LowCardinality(String)](../../sql-reference/data-types/lowcardinality.md)) - For trace type `ProfileEvent` is the name of updated profile event, for other trace types is an empty string.
|
|
- `increment` ([UInt64](../../sql-reference/data-types/int-uint.md)) - For trace type `ProfileEvent` is the amount of increment of profile event, for other trace types is 0.
|
|
|
|
**Example**
|
|
|
|
``` sql
|
|
SELECT * FROM system.trace_log LIMIT 1 \G
|
|
```
|
|
|
|
``` text
|
|
Row 1:
|
|
──────
|
|
hostname: clickhouse.eu-central1.internal
|
|
event_date: 2020-09-10
|
|
event_time: 2020-09-10 11:23:09
|
|
event_time_microseconds: 2020-09-10 11:23:09.872924
|
|
timestamp_ns: 1599762189872924510
|
|
revision: 54440
|
|
trace_type: Memory
|
|
thread_id: 564963
|
|
query_id:
|
|
trace: [371912858,371912789,371798468,371799717,371801313,371790250,624462773,566365041,566440261,566445834,566460071,566459914,566459842,566459580,566459469,566459389,566459341,566455774,371993941,371988245,372158848,372187428,372187309,372187093,372185478,140222123165193,140222122205443]
|
|
size: 5244400
|
|
```
|