- 系统表
- system.server_settings
system.server_settings
在 ClickHouse Cloud 中查询
此系统表中的数据在 ClickHouse Cloud 中的每个节点上本地保存。因此,要获得所有数据的完整视图,需要使用 clusterAllReplicas
函数。有关进一步的详细信息,请参见 这里。
包含关于服务器全局设置的信息,这些设置在 config.xml
中指定。目前,此表仅显示 config.xml
中第一层的设置,并不支持嵌套配置(例如 logger)。
列:
name
(String) — 服务器设置名称。value
(String) — 服务器设置值。default
(String) — 服务器设置默认值。changed
(UInt8) — 显示设置是否在config.xml
中指定。description
(String) — 短的服务器设置描述。type
(String) — 服务器设置值类型。changeable_without_restart
(Enum8) — 设置在服务器运行时是否可以更改。值:'No'
'IncreaseOnly'
'DecreaseOnly'
'Yes'
is_obsolete
(UInt8) - 显示设置是否已过时。
示例
以下示例显示如何获取名称包含 thread_pool
的服务器设置的信息。
SELECT *
FROM system.server_settings
WHERE name LIKE '%thread_pool%'
┌─name──────────────────────────────────────────┬─value─┬─default─┬─changed─┬─description─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬─type───┬─changeable_without_restart─┬─is_obsolete─┐
│ max_thread_pool_size │ 10000 │ 10000 │ 0 │ The maximum number of threads that could be allocated from the OS and used for query execution and background operations. │ UInt64 │ No │ 0 │
│ max_thread_pool_free_size │ 1000 │ 1000 │ 0 │ The maximum number of threads that will always stay in a global thread pool once allocated and remain idle in case of insufficient number of tasks. │ UInt64 │ No │ 0 │
│ thread_pool_queue_size │ 10000 │ 10000 │ 0 │ The maximum number of tasks that will be placed in a queue and wait for execution. │ UInt64 │ No │ 0 │
│ max_io_thread_pool_size │ 100 │ 100 │ 0 │ The maximum number of threads that would be used for IO operations │ UInt64 │ No │ 0 │
│ max_io_thread_pool_free_size │ 0 │ 0 │ 0 │ Max free size for IO thread pool. │ UInt64 │ No │ 0 │
│ io_thread_pool_queue_size │ 10000 │ 10000 │ 0 │ Queue size for IO thread pool. │ UInt64 │ No │ 0 │
│ max_active_parts_loading_thread_pool_size │ 64 │ 64 │ 0 │ The number of threads to load active set of data parts (Active ones) at startup. │ UInt64 │ No │ 0 │
│ max_outdated_parts_loading_thread_pool_size │ 32 │ 32 │ 0 │ The number of threads to load inactive set of data parts (Outdated ones) at startup. │ UInt64 │ No │ 0 │
│ max_unexpected_parts_loading_thread_pool_size │ 32 │ 32 │ 0 │ The number of threads to load inactive set of data parts (Unexpected ones) at startup. │ UInt64 │ No │ 0 │
│ max_parts_cleaning_thread_pool_size │ 128 │ 128 │ 0 │ The number of threads for concurrent removal of inactive data parts. │ UInt64 │ No │ 0 │
│ max_backups_io_thread_pool_size │ 1000 │ 1000 │ 0 │ The maximum number of threads that would be used for IO operations for BACKUP queries │ UInt64 │ No │ 0 │
│ max_backups_io_thread_pool_free_size │ 0 │ 0 │ 0 │ Max free size for backups IO thread pool. │ UInt64 │ No │ 0 │
│ backups_io_thread_pool_queue_size │ 0 │ 0 │ 0 │ Queue size for backups IO thread pool. │ UInt64 │ No │ 0 │
└───────────────────────────────────────────────┴───────┴─────────┴─────────┴─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴────────┴────────────────────────────┴─────────────┘
使用 WHERE changed
可以很有用,例如,当你想检查配置文件中的设置是否正确加载并正在使用时。
SELECT * FROM system.server_settings WHERE changed AND name='max_thread_pool_size'
另请参见