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59 lines
2.1 KiB
Markdown
59 lines
2.1 KiB
Markdown
---
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toc_folder_title: Settings
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toc_priority: 55
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toc_title: Introduction
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---
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# Settings {#session-settings-intro}
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There are multiple ways to make all the settings described in this section of documentation.
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Settings are configured in layers, so each subsequent layer redefines the previous settings.
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Ways to configure settings, in order of priority:
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- Settings in the `users.xml` server configuration file.
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Set in the element `<profiles>`.
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- Session settings.
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Send `SET setting=value` from the ClickHouse console client in interactive mode.
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Similarly, you can use ClickHouse sessions in the HTTP protocol. To do this, you need to specify the `session_id` HTTP parameter.
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- Query settings.
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- When starting the ClickHouse console client in non-interactive mode, set the startup parameter `--setting=value`.
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- When using the HTTP API, pass CGI parameters (`URL?setting_1=value&setting_2=value...`).
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- Make settings in the [SETTINGS](../../sql-reference/statements/select/index.md#settings-in-select) clause of the SELECT query. The setting value is applied only to that query and is reset to default or previous value after the query is executed.
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Settings that can only be made in the server config file are not covered in this section.
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## Custom Settings {#custom_settings}
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In addition to the common [settings](../../operations/settings/settings.md), users can define custom settings.
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A custom setting name must begin with one of predefined prefixes. The list of these prefixes must be declared in the [custom_settings_prefixes](../../operations/server-configuration-parameters/settings.md#custom_settings_prefixes) parameter in the server configuration file.
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```xml
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<custom_settings_prefixes>custom_</custom_settings_prefixes>
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```
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To define a custom setting use `SET` command:
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```sql
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SET custom_a = 123;
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```
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To get the current value of a custom setting use `getSetting()` function:
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```sql
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SELECT getSetting('custom_a');
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```
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**See Also**
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- [Server Configuration Settings](../../operations/server-configuration-parameters/settings.md)
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[Original article](https://clickhouse.com/docs/en/operations/settings/) <!--hide-->
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