mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-16 20:53:27 +00:00
110 lines
4.5 KiB
Markdown
110 lines
4.5 KiB
Markdown
---
|
||
slug: /en/operations/settings/constraints-on-settings
|
||
sidebar_position: 62
|
||
sidebar_label: Constraints on Settings
|
||
---
|
||
|
||
# Constraints on Settings
|
||
|
||
The constraints on settings can be defined in the `profiles` section of the `user.xml` configuration file and prohibit users from changing some of the settings with the `SET` query.
|
||
The constraints are defined as the following:
|
||
|
||
``` xml
|
||
<profiles>
|
||
<user_name>
|
||
<constraints>
|
||
<setting_name_1>
|
||
<min>lower_boundary</min>
|
||
</setting_name_1>
|
||
<setting_name_2>
|
||
<max>upper_boundary</max>
|
||
</setting_name_2>
|
||
<setting_name_3>
|
||
<min>lower_boundary</min>
|
||
<max>upper_boundary</max>
|
||
</setting_name_3>
|
||
<setting_name_4>
|
||
<readonly/>
|
||
</setting_name_4>
|
||
<setting_name_5>
|
||
<min>lower_boundary</min>
|
||
<max>upper_boundary</max>
|
||
<changeable_in_readonly/>
|
||
</setting_name_5>
|
||
</constraints>
|
||
</user_name>
|
||
</profiles>
|
||
```
|
||
|
||
If the user tries to violate the constraints an exception is thrown and the setting isn’t changed.
|
||
There are supported few types of constraints: `min`, `max`, `readonly` (with alias `const`) and `changeable_in_readonly`. The `min` and `max` constraints specify upper and lower boundaries for a numeric setting and can be used in combination. The `readonly` or `const` constraint specifies that the user cannot change the corresponding setting at all. The `changeable_in_readonly` constraint type allows user to change the setting within `min`/`max` range even if `readonly` setting is set to 1, otherwise settings are not allow to be changed in `readonly=1` mode. Note that `changeable_in_readonly` is supported only if `settings_constraints_replace_previous` is enabled:
|
||
``` xml
|
||
<access_control_improvements>
|
||
<settings_constraints_replace_previous>true</settings_constraints_replace_previous>
|
||
</access_control_improvements>
|
||
```
|
||
|
||
If there are multiple profiles active for a user, then constraints are merged. Merge process depends on `settings_constraints_replace_previous`:
|
||
- **true** (recommended): constraints for the same setting are replaced during merge, such that the last constraint is used and all previous are ignored including fields that are not set in new constraint.
|
||
- **false** (default): constraints for the same setting are merged in a way that every not set type of constraint is taken from previous profile and every set type of constraint is replaced by value from new profile.
|
||
|
||
Read-only mode is enabled by `readonly` setting (not to confuse with `readonly` constraint type):
|
||
- `readonly=0`: No read-only restrictions.
|
||
- `readonly=1`: Only read queries are allowed and settings cannot be changed unless `changeable_in_readonly` is set.
|
||
- `readonly=2`: Only read queries are allowed, but settings can be changed, except for `readonly` setting itself.
|
||
|
||
|
||
**Example:** Let `users.xml` includes lines:
|
||
|
||
``` xml
|
||
<profiles>
|
||
<default>
|
||
<max_memory_usage>10000000000</max_memory_usage>
|
||
<force_index_by_date>0</force_index_by_date>
|
||
...
|
||
<constraints>
|
||
<max_memory_usage>
|
||
<min>5000000000</min>
|
||
<max>20000000000</max>
|
||
</max_memory_usage>
|
||
<force_index_by_date>
|
||
<readonly/>
|
||
</force_index_by_date>
|
||
</constraints>
|
||
</default>
|
||
</profiles>
|
||
```
|
||
|
||
The following queries all throw exceptions:
|
||
|
||
``` sql
|
||
SET max_memory_usage=20000000001;
|
||
SET max_memory_usage=4999999999;
|
||
SET force_index_by_date=1;
|
||
```
|
||
|
||
``` text
|
||
Code: 452, e.displayText() = DB::Exception: Setting max_memory_usage should not be greater than 20000000000.
|
||
Code: 452, e.displayText() = DB::Exception: Setting max_memory_usage should not be less than 5000000000.
|
||
Code: 452, e.displayText() = DB::Exception: Setting force_index_by_date should not be changed.
|
||
```
|
||
|
||
**Note:** the `default` profile has special handling: all the constraints defined for the `default` profile become the default constraints, so they restrict all the users until they’re overridden explicitly for these users.
|
||
|
||
## Constraints on Merge Tree Settings
|
||
It is possible to set constraints for [merge tree settings](merge-tree-settings.md). These constraints are applied when table with merge tree engine is created or its storage settings are altered. Name of merge tree setting must be prepended by `merge_tree_` prefix when referenced in `<constraints>` section.
|
||
|
||
**Example:** Forbid to create new tables with explicitly specified `storage_policy`
|
||
|
||
``` xml
|
||
<profiles>
|
||
<default>
|
||
<constraints>
|
||
<merge_tree_storage_policy>
|
||
<const/>
|
||
</merge_tree_storage_policy>
|
||
</constraints>
|
||
</default>
|
||
</profiles>
|
||
```
|