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49
docs/en/operations/backup.md
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@ -206,6 +206,55 @@ end_time: 2022-08-30 09:21:46
1 row in set. Elapsed: 0.002 sec.
```
Along with `system.backups` table, all backup and restore operations are also tracked in the system log table [backup_log](../operations/system-tables/backup_log.md):
```
SELECT *
FROM system.backup_log
WHERE id = '7678b0b3-f519-4e6e-811f-5a0781a4eb52'
ORDER BY event_time_microseconds ASC
FORMAT Vertical
```
```response
Row 1:
──────
event_date: 2023-08-18
event_time_microseconds: 2023-08-18 11:13:43.097414
id: 7678b0b3-f519-4e6e-811f-5a0781a4eb52
name: Disk('backups', '1.zip')
status: CREATING_BACKUP
error:
start_time: 2023-08-18 11:13:43
end_time: 1970-01-01 03:00:00
num_files: 0
total_size: 0
num_entries: 0
uncompressed_size: 0
compressed_size: 0
files_read: 0
bytes_read: 0
Row 2:
──────
event_date: 2023-08-18
event_time_microseconds: 2023-08-18 11:13:43.174782
id: 7678b0b3-f519-4e6e-811f-5a0781a4eb52
name: Disk('backups', '1.zip')
status: BACKUP_FAILED
#highlight-next-line
error: Code: 598. DB::Exception: Backup Disk('backups', '1.zip') already exists. (BACKUP_ALREADY_EXISTS) (version 23.8.1.1)
start_time: 2023-08-18 11:13:43
end_time: 2023-08-18 11:13:43
num_files: 0
total_size: 0
num_entries: 0
uncompressed_size: 0
compressed_size: 0
files_read: 0
bytes_read: 0
2 rows in set. Elapsed: 0.075 sec.
```
## Configuring BACKUP/RESTORE to use an S3 Endpoint
To write backups to an S3 bucket you need three pieces of information:

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docs/en/operations/server-configuration-parameters/settings.md
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@ -2084,6 +2084,47 @@ The default server configuration file `config.xml` contains the following settin
</crash_log>
```
## backup_log {#server_configuration_parameters-backup_log}
Settings for the [backup_log](../../operations/system-tables/backup_log.md) system table for logging `BACKUP` and `RESTORE` operations.
Parameters:
- `database` — Database name.
- `table` — Table name.
- `partition_by` — [Custom partitioning key](../../engines/table-engines/mergetree-family/custom-partitioning-key.md) for a system table. Can't be used if `engine` is defined.
- `order_by` - [Custom sorting key](../../engines/table-engines/mergetree-family/mergetree.md#order_by) for a system table. Can't be used if `engine` is defined.
- `engine` - [MergeTree Engine Definition](../../engines/table-engines/mergetree-family/mergetree.md#table_engine-mergetree-creating-a-table) for a system table. Can't be used if `partition_by` or `order_by` is defined.
- `flush_interval_milliseconds` — Interval for flushing data from the buffer in memory to the table.
- `max_size_rows` – Maximal size in lines for the logs. When non-flushed logs amount reaches max_size, logs dumped to the disk.
Default: 1048576.
- `reserved_size_rows` – Pre-allocated memory size in lines for the logs.
Default: 8192.
- `buffer_size_rows_flush_threshold` – Lines amount threshold, reaching it launches flushing logs to the disk in background.
Default: `max_size_rows / 2`.
- `flush_on_crash` - Indication whether logs should be dumped to the disk in case of a crash.
Default: false.
- `storage_policy` – Name of storage policy to use for the table (optional).
- `settings` - [Additional parameters](../../engines/table-engines/mergetree-family/mergetree.md#settings) that control the behavior of the MergeTree (optional).
**Example**
```xml
<clickhouse>
<backup_log>
<database>system</database>
<table>backup_log</table>
<flush_interval_milliseconds>1000</flush_interval_milliseconds>
<partition_by>toYYYYMM(event_date)</partition_by>
<max_size_rows>1048576</max_size_rows>
<reserved_size_rows>8192</reserved_size_rows>
<buffer_size_rows_flush_threshold>524288</buffer_size_rows_flush_threshold>
<flush_on_crash>false</flush_on_crash>
<!-- <engine>Engine = MergeTree PARTITION BY event_date ORDER BY event_time TTL event_date + INTERVAL 30 day</engine> -->
</backup_log>
</clickhouse>
```
## query_masking_rules {#query-masking-rules}
Regexp-based rules, which will be applied to queries as well as all log messages before storing them in server logs,

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@ -0,0 +1,145 @@
---
slug: /en/operations/system-tables/backup_log
---
# backup_log
Contains logging entries with the information about `BACKUP` and `RESTORE` operations.
Columns:
- `event_date` ([Date](../../sql-reference/data-types/date.md)) — Date of the entry.
- `event_time_microseconds` ([DateTime64](../../sql-reference/data-types/datetime64.md)) — Time of the entry with microseconds precision.
- `id` ([String](../../sql-reference/data-types/string.md)) — Identifier of the backup or restore operation.
- `name` ([String](../../sql-reference/data-types/string.md)) — Name of the backup storage (the contents of the `FROM` or `TO` clause).
- `status` ([Enum8](../../sql-reference/data-types/enum.md)) — Operation status. Possible values:
- `'CREATING_BACKUP'`
- `'BACKUP_CREATED'`
- `'BACKUP_FAILED'`
- `'RESTORING'`
- `'RESTORED'`
- `'RESTORE_FAILED'`
- `error` ([String](../../sql-reference/data-types/string.md)) — Error message of the failed operation (empty string for successful opetations).
- `start_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Start time of the operation.
- `end_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — End time of the operation.
- `num_files` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Number of files stored in the backup.
- `total_size` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Total size of files stored in the backup.
- `num_entries` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Number of entries in the backup, i.e. the number of files inside the folder if the backup is stored as a folder, or the number of files inside the archive if the backup is stored as an archive. It is not the same as `num_files` if it's an incremental backup or if it contains empty files or duplicates. The following is always true: `num_entries <= num_files`.
- `uncompressed_size` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Uncompressed size of the backup.
- `compressed_size` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Compressed size of the backup. If the backup is not stored as an archive it equals to `uncompressed_size`.
- `files_read` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Number of files read during the restore operation.
- `bytes_read` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Total size of files read during the restore operation.
**Example**
```sql
BACKUP TABLE test_db.my_table TO Disk('backups_disk', '1.zip')
```
```response
┌─id───────────────────────────────────┬─status─────────┐
│ e5b74ecb-f6f1-426a-80be-872f90043885 │ BACKUP_CREATED │
└──────────────────────────────────────┴────────────────┘
```
```sql
SELECT * FROM system.backup_log WHERE id = 'e5b74ecb-f6f1-426a-80be-872f90043885' ORDER BY event_date, event_time_microseconds \G
```
```response
Row 1:
──────
event_date: 2023-08-19
event_time_microseconds: 2023-08-19 11:05:21.998566
id: e5b74ecb-f6f1-426a-80be-872f90043885
name: Disk('backups_disk', '1.zip')
status: CREATING_BACKUP
error:
start_time: 2023-08-19 11:05:21
end_time: 1970-01-01 03:00:00
num_files: 0
total_size: 0
num_entries: 0
uncompressed_size: 0
compressed_size: 0
files_read: 0
bytes_read: 0
Row 2:
──────
event_date: 2023-08-19
event_time_microseconds: 2023-08-19 11:08:56.916192
id: e5b74ecb-f6f1-426a-80be-872f90043885
name: Disk('backups_disk', '1.zip')
status: BACKUP_CREATED
error:
start_time: 2023-08-19 11:05:21
end_time: 2023-08-19 11:08:56
num_files: 57
total_size: 4290364870
num_entries: 46
uncompressed_size: 4290362365
compressed_size: 3525068304
files_read: 0
bytes_read: 0
```
```sql
RESTORE TABLE test_db.my_table FROM Disk('backups_disk', '1.zip')
```
```response
┌─id───────────────────────────────────┬─status───┐
│ cdf1f731-52ef-42da-bc65-2e1bfcd4ce90 │ RESTORED │
└──────────────────────────────────────┴──────────┘
```
```sql
SELECT * FROM system.backup_log WHERE id = 'cdf1f731-52ef-42da-bc65-2e1bfcd4ce90' ORDER BY event_date, event_time_microseconds \G
```
```response
Row 1:
──────
event_date: 2023-08-19
event_time_microseconds: 2023-08-19 11:09:19.718077
id: cdf1f731-52ef-42da-bc65-2e1bfcd4ce90
name: Disk('backups_disk', '1.zip')
status: RESTORING
error:
start_time: 2023-08-19 11:09:19
end_time: 1970-01-01 03:00:00
num_files: 0
total_size: 0
num_entries: 0
uncompressed_size: 0
compressed_size: 0
files_read: 0
bytes_read: 0
Row 2:
──────
event_date: 2023-08-19
event_time_microseconds: 2023-08-19 11:09:29.334234
id: cdf1f731-52ef-42da-bc65-2e1bfcd4ce90
name: Disk('backups_disk', '1.zip')
status: RESTORED
error:
start_time: 2023-08-19 11:09:19
end_time: 2023-08-19 11:09:29
num_files: 57
total_size: 4290364870
num_entries: 46
uncompressed_size: 4290362365
compressed_size: 4290362365
files_read: 57
bytes_read: 4290364870
```
This is essentially the same information that is written in the system table `system.backups`:
```sql
SELECT * FROM system.backups ORDER BY start_time
```
```response
┌─id───────────────────────────────────┬─name──────────────────────────┬─status─────────┬─error─┬──────────start_time─┬────────────end_time─┬─num_files─┬─total_size─┬─num_entries─┬─uncompressed_size─┬─compressed_size─┬─files_read─┬─bytes_read─┐
│ e5b74ecb-f6f1-426a-80be-872f90043885 │ Disk('backups_disk', '1.zip') │ BACKUP_CREATED │ │ 2023-08-19 11:05:21 │ 2023-08-19 11:08:56 │ 57 │ 4290364870 │ 46 │ 4290362365 │ 3525068304 │ 0 │ 0 │
│ cdf1f731-52ef-42da-bc65-2e1bfcd4ce90 │ Disk('backups_disk', '1.zip') │ RESTORED │ │ 2023-08-19 11:09:19 │ 2023-08-19 11:09:29 │ 57 │ 4290364870 │ 46 │ 4290362365 │ 4290362365 │ 57 │ 4290364870 │
└──────────────────────────────────────┴───────────────────────────────┴────────────────┴───────┴─────────────────────┴─────────────────────┴───────────┴────────────┴─────────────┴───────────────────┴─────────────────┴────────────┴────────────┘
```
**See Also**
- [Backup and Restore](../../operations/backup.md)

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@ -23,7 +23,7 @@ System tables:
Most of system tables store their data in RAM. A ClickHouse server creates such system tables at the start.
Unlike other system tables, the system log tables [metric_log](../../operations/system-tables/metric_log.md), [query_log](../../operations/system-tables/query_log.md), [query_thread_log](../../operations/system-tables/query_thread_log.md), [trace_log](../../operations/system-tables/trace_log.md), [part_log](../../operations/system-tables/part_log.md), [crash_log](../../operations/system-tables/crash-log.md) and [text_log](../../operations/system-tables/text_log.md) are served by [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) table engine and store their data in a filesystem by default. If you remove a table from a filesystem, the ClickHouse server creates the empty one again at the time of the next data writing. If system table schema changed in a new release, then ClickHouse renames the current table and creates a new one.
Unlike other system tables, the system log tables [metric_log](../../operations/system-tables/metric_log.md), [query_log](../../operations/system-tables/query_log.md), [query_thread_log](../../operations/system-tables/query_thread_log.md), [trace_log](../../operations/system-tables/trace_log.md), [part_log](../../operations/system-tables/part_log.md), [crash_log](../../operations/system-tables/crash-log.md), [text_log](../../operations/system-tables/text_log.md) and [backup_log](../../operations/system-tables/backup_log.md) are served by [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) table engine and store their data in a filesystem by default. If you remove a table from a filesystem, the ClickHouse server creates the empty one again at the time of the next data writing. If system table schema changed in a new release, then ClickHouse renames the current table and creates a new one.
System log tables can be customized by creating a config file with the same name as the table under `/etc/clickhouse-server/config.d/`, or setting corresponding elements in `/etc/clickhouse-server/config.xml`. Elements can be customized are:
@ -32,7 +32,7 @@ System log tables can be customized by creating a config file with the same name
- `partition_by`: specify [PARTITION BY](../../engines/table-engines/mergetree-family/custom-partitioning-key.md) expression.
- `ttl`: specify table [TTL](../../sql-reference/statements/alter/ttl.md) expression.
- `flush_interval_milliseconds`: interval of flushing data to disk.
- `engine`: provide full engine expression (starting with `ENGINE =` ) with parameters. This option is contradict with `partition_by` and `ttl`. If set together, the server would raise an exception and exit.
- `engine`: provide full engine expression (starting with `ENGINE =` ) with parameters. This option conflicts with `partition_by` and `ttl`. If set together, the server will raise an exception and exit.
An example:

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@ -1488,6 +1488,47 @@ ClickHouse использует потоки из глобального пул
</crash_log>
```
## backup_log {#server_configuration_parameters-backup_log}
Настройки для системной таблицы [backup_log](../../operations/system-tables/backup_log.md), предназначенной для логирования операций `BACKUP` и `RESTORE`.
Параметры:
- `database` — имя базы данных.
- `table` — имя таблицы.
- `partition_by` — [произвольный ключ партиционирования](../../engines/table-engines/mergetree-family/custom-partitioning-key.md). Нельзя использовать одновременно с `engine`.
- `order_by` - [произвольный ключ сортировки](../../engines/table-engines/mergetree-family/mergetree.md#order_by). Нельзя использовать одновременно с `engine`.
- `engine` - [настройки MergeTree Engine](../../engines/table-engines/mergetree-family/mergetree.md#table_engine-mergetree-creating-a-table). Нельзя использовать с `partition_by` или `order_by`.
- `flush_interval_milliseconds` — период сброса данных из буфера в памяти в таблицу.
- `max_size_rows` – максимальный размер в строках для буфера с логами. Когда буфер будет заполнен полностью, сбрасывает логи на диск.
Значение по умолчанию: 1024.
- `reserved_size_rows` – преаллоцированный размер в строках для буфера с логами.
Значение по умолчанию: 1024.
- `buffer_size_rows_flush_threshold` – количество строк в логе, при достижении которого логи начнут скидываться на диск в неблокирующем режиме.
Значение по умолчанию: `max_size_rows / 2`.
- `flush_on_crash` - должны ли логи быть сброшены на диск в случае неожиданной остановки программы.
Значение по умолчанию: false.
- `storage_policy` – название политики хранения (необязательный параметр).
- `settings` - [дополнительные настройки MergeTree Engine](../../engines/table-engines/mergetree-family/mergetree.md#settings) (необязательный параметр).
**Пример**
```xml
<clickhouse>
<backup_log>
<database>system</database>
<table>backup_log</table>
<flush_interval_milliseconds>1000</flush_interval_milliseconds>
<partition_by>toYYYYMM(event_date)</partition_by>
<max_size_rows>1048576</max_size_rows>
<reserved_size_rows>8192</reserved_size_rows>
<buffer_size_rows_flush_threshold>524288</buffer_size_rows_flush_threshold>
<flush_on_crash>false</flush_on_crash>
<!-- <engine>Engine = MergeTree PARTITION BY event_date ORDER BY event_time TTL event_date + INTERVAL 30 day</engine> -->
</backup_log>
</clickhouse>
```
## query_masking_rules {#query-masking-rules}
Правила, основанные на регулярных выражениях, которые будут применены для всех запросов, а также для всех сообщений перед сохранением их в лог на сервере,

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@ -0,0 +1,145 @@
---
slug: /ru/operations/system-tables/backup_log
---
# system.backup_log {#system_tables-backup-log}
Содержит информацию о всех операциях `BACKUP` and `RESTORE`.
Колонки:
- `event_date` ([Date](../../sql-reference/data-types/date.md)) — Дата события.
- `event_time_microseconds` ([DateTime64](../../sql-reference/data-types/datetime64.md)) — Время события с точностью до микросекунд.
- `id` ([String](../../sql-reference/data-types/string.md)) — Идентификатор операции.
- `name` ([String](../../sql-reference/data-types/string.md)) — Название хранилища (содержимое секции `FROM` или `TO` в SQL запросе).
- `status` ([Enum8](../../sql-reference/data-types/enum.md)) — Статус операции. Возможные значения:
- `'CREATING_BACKUP'`
- `'BACKUP_CREATED'`
- `'BACKUP_FAILED'`
- `'RESTORING'`
- `'RESTORED'`
- `'RESTORE_FAILED'`
- `error` ([String](../../sql-reference/data-types/string.md)) — Сообщение об ошибке, при наличии (записи для успешных операций содержат пустую строку).
- `start_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Время начала операции.
- `end_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Время завершения операции.
- `num_files` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Количество файлов, хранимых в бэкапе.
- `total_size` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Общий размер файлов, хранимых в бэкапе.
- `num_entries` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Количество позиций в бэкапе, т.е. либо количество файлов в папке (если бэкап хранится в папке), либо количество файлов в архиве (если бэкап хранится в архиве). Это значение не равно `num_files` в случае если это инкрементальный бэкап либо он содержит пустые файлы или дубликаты. Следующее утверждение верно всегда: `num_entries <= num_files`.
- `uncompressed_size` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Размер бэкапа до сжатия.
- `compressed_size` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Размер бэкапа после сжатия. Если бэкап не хранится в виде архива, это значение равно `uncompressed_size`.
- `files_read` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Количество файлов, прочитанных во время операции восстановления.
- `bytes_read` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Общий размер файлов, прочитанных во время операции восстановления.
**Пример**
```sql
BACKUP TABLE test_db.my_table TO Disk('backups_disk', '1.zip')
```
```response
┌─id───────────────────────────────────┬─status─────────┐
│ e5b74ecb-f6f1-426a-80be-872f90043885 │ BACKUP_CREATED │
└──────────────────────────────────────┴────────────────┘
```
```sql
SELECT * FROM system.backup_log WHERE id = 'e5b74ecb-f6f1-426a-80be-872f90043885' ORDER BY event_date, event_time_microseconds \G
```
```response
Row 1:
──────
event_date: 2023-08-19
event_time_microseconds: 2023-08-19 11:05:21.998566
id: e5b74ecb-f6f1-426a-80be-872f90043885
name: Disk('backups_disk', '1.zip')
status: CREATING_BACKUP
error:
start_time: 2023-08-19 11:05:21
end_time: 1970-01-01 03:00:00
num_files: 0
total_size: 0
num_entries: 0
uncompressed_size: 0
compressed_size: 0
files_read: 0
bytes_read: 0
Row 2:
──────
event_date: 2023-08-19
event_time_microseconds: 2023-08-19 11:08:56.916192
id: e5b74ecb-f6f1-426a-80be-872f90043885
name: Disk('backups_disk', '1.zip')
status: BACKUP_CREATED
error:
start_time: 2023-08-19 11:05:21
end_time: 2023-08-19 11:08:56
num_files: 57
total_size: 4290364870
num_entries: 46
uncompressed_size: 4290362365
compressed_size: 3525068304
files_read: 0
bytes_read: 0
```
```sql
RESTORE TABLE test_db.my_table FROM Disk('backups_disk', '1.zip')
```
```response
┌─id───────────────────────────────────┬─status───┐
│ cdf1f731-52ef-42da-bc65-2e1bfcd4ce90 │ RESTORED │
└──────────────────────────────────────┴──────────┘
```
```sql
SELECT * FROM system.backup_log WHERE id = 'cdf1f731-52ef-42da-bc65-2e1bfcd4ce90' ORDER BY event_date, event_time_microseconds \G
```
```response
Row 1:
──────
event_date: 2023-08-19
event_time_microseconds: 2023-08-19 11:09:19.718077
id: cdf1f731-52ef-42da-bc65-2e1bfcd4ce90
name: Disk('backups_disk', '1.zip')
status: RESTORING
error:
start_time: 2023-08-19 11:09:19
end_time: 1970-01-01 03:00:00
num_files: 0
total_size: 0
num_entries: 0
uncompressed_size: 0
compressed_size: 0
files_read: 0
bytes_read: 0
Row 2:
──────
event_date: 2023-08-19
event_time_microseconds: 2023-08-19 11:09:29.334234
id: cdf1f731-52ef-42da-bc65-2e1bfcd4ce90
name: Disk('backups_disk', '1.zip')
status: RESTORED
error:
start_time: 2023-08-19 11:09:19
end_time: 2023-08-19 11:09:29
num_files: 57
total_size: 4290364870
num_entries: 46
uncompressed_size: 4290362365
compressed_size: 4290362365
files_read: 57
bytes_read: 4290364870
```
Это по сути та же информация, что заносится и в системную таблицу `system.backups`:
```sql
SELECT * FROM system.backups ORDER BY start_time
```
```response
┌─id───────────────────────────────────┬─name──────────────────────────┬─status─────────┬─error─┬──────────start_time─┬────────────end_time─┬─num_files─┬─total_size─┬─num_entries─┬─uncompressed_size─┬─compressed_size─┬─files_read─┬─bytes_read─┐
│ e5b74ecb-f6f1-426a-80be-872f90043885 │ Disk('backups_disk', '1.zip') │ BACKUP_CREATED │ │ 2023-08-19 11:05:21 │ 2023-08-19 11:08:56 │ 57 │ 4290364870 │ 46 │ 4290362365 │ 3525068304 │ 0 │ 0 │
│ cdf1f731-52ef-42da-bc65-2e1bfcd4ce90 │ Disk('backups_disk', '1.zip') │ RESTORED │ │ 2023-08-19 11:09:19 │ 2023-08-19 11:09:29 │ 57 │ 4290364870 │ 46 │ 4290362365 │ 4290362365 │ 57 │ 4290364870 │
└──────────────────────────────────────┴───────────────────────────────┴────────────────┴───────┴─────────────────────┴─────────────────────┴───────────┴────────────┴─────────────┴───────────────────┴─────────────────┴────────────┴────────────┘
```
**См. также**
- [Backup and Restore](../../operations/backup.md)

2
docs/ru/operations/system-tables/index.md
View File

@ -21,7 +21,7 @@ sidebar_label: "Системные таблицы"
Большинство системных таблиц хранят свои данные в оперативной памяти. Сервер ClickHouse создает эти системные таблицы при старте.
В отличие от других системных таблиц, таблицы с системными логами [metric_log](../../operations/system-tables/metric_log.md), [query_log](../../operations/system-tables/query_log.md), [query_thread_log](../../operations/system-tables/query_thread_log.md), [trace_log](../../operations/system-tables/trace_log.md), [part_log](../../operations/system-tables/part_log.md), [crash_log](../../operations/system-tables/crash-log.md) и [text_log](../../operations/system-tables/text_log.md) используют движок таблиц [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) и по умолчанию хранят свои данные в файловой системе. Если удалить таблицу из файловой системы, сервер ClickHouse снова создаст пустую таблицу во время следующей записи данных. Если схема системной таблицы изменилась в новом релизе, то ClickHouse переименует текущую таблицу и создаст новую.
В отличие от других системных таблиц, таблицы с системными логами [metric_log](../../operations/system-tables/metric_log.md), [query_log](../../operations/system-tables/query_log.md), [query_thread_log](../../operations/system-tables/query_thread_log.md), [trace_log](../../operations/system-tables/trace_log.md), [part_log](../../operations/system-tables/part_log.md), [crash_log](../../operations/system-tables/crash-log.md), [text_log](../../operations/system-tables/text_log.md) и [backup_log](../../operations/system-tables/backup_log.md) используют движок таблиц [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) и по умолчанию хранят свои данные в файловой системе. Если удалить таблицу из файловой системы, сервер ClickHouse снова создаст пустую таблицу во время следующей записи данных. Если схема системной таблицы изменилась в новом релизе, то ClickHouse переименует текущую таблицу и создаст новую.
Таблицы с системными логами `log` можно настроить, создав конфигурационный файл с тем же именем, что и таблица в разделе `/etc/clickhouse-server/config.d/`, или указав соответствующие элементы в `/etc/clickhouse-server/config.xml`. Настраиваться могут следующие элементы: