mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-10-09 01:50:50 +00:00
51 lines
2.5 KiB
Markdown
51 lines
2.5 KiB
Markdown
<a name="dicts-external_dicts"></a>
|
||
|
||
# External Dictionaries
|
||
|
||
You can add your own dictionaries from various data sources. The data source for a dictionary can be a local text or executable file, an HTTP(s) resource, or another DBMS. For more information, see "[Sources of external dictionaries](external_dicts_dict_sources.md#dicts-external_dicts_dict_sources)".
|
||
|
||
ClickHouse:
|
||
|
||
- Fully or partially stores dictionaries in RAM.
|
||
- Periodically updates dictionaries and dynamically loads missing values. In other words, dictionaries can be loaded dynamically.
|
||
|
||
The configuration of external dictionaries is located in one or more files. The path to the configuration is specified in the [dictionaries_config](../../operations/server_settings/settings.md#server_settings-dictionaries_config) parameter.
|
||
|
||
Dictionaries can be loaded at server startup or at first use, depending on the [dictionaries_lazy_load](../../operations/server_settings/settings.md#server_settings-dictionaries_lazy_load) setting.
|
||
|
||
The dictionary config file has the following format:
|
||
|
||
```xml
|
||
<yandex>
|
||
<comment>An optional element with any content. Ignored by the ClickHouse server.</comment>
|
||
|
||
<!--Optional element. File name with substitutions-->
|
||
<include_from>/etc/metrika.xml</include_from>
|
||
|
||
|
||
<dictionary>
|
||
<!-- Dictionary configuration -->
|
||
</dictionary>
|
||
|
||
...
|
||
|
||
<dictionary>
|
||
<!-- Dictionary configuration -->
|
||
</dictionary>
|
||
</yandex>
|
||
```
|
||
|
||
You can [configure](external_dicts_dict.md#dicts-external_dicts_dict) any number of dictionaries in the same file. The file format is preserved even if there is only one dictionary (i.e. `<yandex><dictionary> <!--configuration -> </dictionary></yandex>` ).
|
||
|
||
> You can convert values for a small dictionary by describing it in a `SELECT` query (see the [transform](../functions/other_functions.md#other_functions-transform) function). This functionality is not related to external dictionaries.
|
||
|
||
See also:
|
||
|
||
- [Configuring an external dictionary](external_dicts_dict.md#dicts-external_dicts_dict)
|
||
- [Storing dictionaries in memory](external_dicts_dict_layout.md#dicts-external_dicts_dict_layout)
|
||
- [Updating dictionaries](external_dicts_dict_lifetime#dicts-external_dicts_dict_lifetime)
|
||
- [Sources of external dictionaries](external_dicts_dict_sources.md#dicts-external_dicts_dict_sources)
|
||
- [Dictionary key and fields](external_dicts_dict_structure.md#dicts-external_dicts_dict_dict_structure)
|
||
- [Functions for working with external dictionaries](../functions/ext_dict_functions.md#ext_dict_functions)
|
||
|