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Settings Overview

Overview​

Note

XML-based Settings Profiles and configuration files are currently not supported for ClickHouse Cloud. To specify settings for your ClickHouse Cloud service, you must use SQL-driven Settings Profiles.

There are following main groups of ClickHouse settings:

  • Global server settings
  • Session settings
  • Query settings
  • Background operations settings

Global settings apply by default unless overridden at further levels. Session settings can be specified via profiles, user configuration and SET commands. Query settings can be provided via SETTINGS clause and are applied to individual queries. Background operations settings are applied to Mutations, Merges and potentially other operations, executed asynchronously in the background.

Viewing non-default settings​

To view which settings have been changed from their default value you can query the system.settings table:

SELECT name, value FROM system.settings WHERE changed

If no settings have been changed from their default value, then ClickHouse will return nothing.

To check the value of a particular setting, you can specify the name of the setting in your query:

SELECT name, value FROM system.settings WHERE name = 'max_threads'

Which will return something like this:

┌─name────────┬─value─────┐
│ max_threads │ 'auto(8)' │
└─────────────┴───────────┘

1 row in set. Elapsed: 0.002 sec.

Further reading​

  • See global server settings to learn more about configuring your ClickHouse server at the global server level.
  • See session settings to learn more about configuring your ClickHouse server at the session level.
  • See context hierarchy to learn more about configuration processing by Clickhouse.