ClickHouse/docs/ru/query_language/dicts/external_dicts_dict_structure.md

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# Ключ и поля словаря
Секция `<structure>` описывает ключ словаря и поля, доступные для запросов.
Общий вид структуры:
```xml
<dictionary>
<structure>
<id>
<name>Id</name>
</id>
<attribute>
<!-- Attribute parameters -->
</attribute>
...
</structure>
</dictionary>
```
В структуре описываются столбцы:
- `<id>` — [ключевой столбец](external_dicts_dict_structure.md#ext_dict_structure-key).
- `<attribute>` — [столбец данных](external_dicts_dict_structure.md#ext_dict_structure-attributes). Столбцов может быть много.
## Ключ {#ext_dict_structure-key}
ClickHouse поддерживает следующие виды ключей:
- Числовой ключ. UInt64. Описывается в теге `<id>`.
- Составной ключ. Набор значений разного типа. Описывается в теге `<key>`.
Структура может содержать либо `<id>` либо `<key>`.
!!! warning "Обратите внимание"
WIP on documentation (#2692) * Additional .gitignore entries * Merge a bunch of small articles about system tables into single one * Merge a bunch of small articles about formats into single one * Adapt table with formats to English docs too * Add SPb meetup link to main page * Move Utilities out of top level of docs (the location is probably not yet final) + translate couple articles * Merge MacOS.md into build_osx.md * Move Data types higher in ToC * Publish changelog on website alongside documentation * Few fixes for en/table_engines/file.md * Use smaller header sizes in changelogs * Group up table engines inside ToC * Move table engines out of top level too * Specificy in ToC that query language is SQL based. Thats a bit excessive, but catches eye. * Move stuff that is part of query language into respective folder * Move table functions lower in ToC * Lost redirects.txt update * Do not rely on comments in yaml + fix few ru titles * Extract major parts of queries.md into separate articles * queries.md has been supposed to be removed * Fix weird translation * Fix a bunch of links * There is only table of contents left * "Query language" is actually part of SQL abbreviation * Change filename in README.md too * fix mistype * s/formats\/interfaces/interfaces\/formats/g * Remove extra clarification from header as it was too verbose, probably making it a bit more confusing * Empty article was supposed to be hidden * At least change incorrect title * Move special links to the bottom of nav and slightly highlight them * Skip hidden pages in bottom navigation too * Make front page of documentation to be part of Introduction * Make tables in introduction somewhat readable + move abbreviation definitions earlier * Some introduction text refactoring * Some docs introduction refactoring * Use admonitions instead of divs * Additional .gitignore * Treat .gif as images too * Clarify ToC item
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Ключ не надо дополнительно описывать в атрибутах.
### Числовой ключ
Тип: `UInt64`.
Пример конфигурации:
```xml
<id>
<name>Id</name>
</id>
```
Поля конфигурации:
- `name` — имя столбца с ключами.
### Составной ключ
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Ключом может быть кортеж (`tuple`) из полей произвольных типов. В этом случае [layout](external_dicts_dict_layout.md) должен быть `complex_key_hashed` или `complex_key_cache`.
WIP on documentation (#2692) * Additional .gitignore entries * Merge a bunch of small articles about system tables into single one * Merge a bunch of small articles about formats into single one * Adapt table with formats to English docs too * Add SPb meetup link to main page * Move Utilities out of top level of docs (the location is probably not yet final) + translate couple articles * Merge MacOS.md into build_osx.md * Move Data types higher in ToC * Publish changelog on website alongside documentation * Few fixes for en/table_engines/file.md * Use smaller header sizes in changelogs * Group up table engines inside ToC * Move table engines out of top level too * Specificy in ToC that query language is SQL based. Thats a bit excessive, but catches eye. * Move stuff that is part of query language into respective folder * Move table functions lower in ToC * Lost redirects.txt update * Do not rely on comments in yaml + fix few ru titles * Extract major parts of queries.md into separate articles * queries.md has been supposed to be removed * Fix weird translation * Fix a bunch of links * There is only table of contents left * "Query language" is actually part of SQL abbreviation * Change filename in README.md too * fix mistype * s/formats\/interfaces/interfaces\/formats/g * Remove extra clarification from header as it was too verbose, probably making it a bit more confusing * Empty article was supposed to be hidden * At least change incorrect title * Move special links to the bottom of nav and slightly highlight them * Skip hidden pages in bottom navigation too * Make front page of documentation to be part of Introduction * Make tables in introduction somewhat readable + move abbreviation definitions earlier * Some introduction text refactoring * Some docs introduction refactoring * Use admonitions instead of divs * Additional .gitignore * Treat .gif as images too * Clarify ToC item
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!!! tip "Совет"
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Составной ключ может состоять из одного элемента. Это даёт возможность использовать в качестве ключа, например, строку.
WIP on docs (#3813) * CLICKHOUSE-4063: less manual html @ index.md * CLICKHOUSE-4063: recommend markdown="1" in README.md * CLICKHOUSE-4003: manually purge custom.css for now * CLICKHOUSE-4064: expand <details> before any print (including to pdf) * CLICKHOUSE-3927: rearrange interfaces/formats.md a bit * CLICKHOUSE-3306: add few http headers * Remove copy-paste introduced in #3392 * Hopefully better chinese fonts #3392 * get rid of tabs @ custom.css * Apply comments and patch from #3384 * Add jdbc.md to ToC and some translation, though it still looks badly incomplete * minor punctuation * Add some backlinks to official website from mirrors that just blindly take markdown sources * Do not make fonts extra light * find . -name '*.md' -type f | xargs -I{} perl -pi -e 's//g' {} * find . -name '*.md' -type f | xargs -I{} perl -pi -e 's/ sql/g' {} * Remove outdated stuff from roadmap.md * Not so light font on front page too * Refactor Chinese formats.md to match recent changes in other languages * Update some links on front page * Remove some outdated comment * Add twitter link to front page * More front page links tuning * Add Amsterdam meetup link * Smaller font to avoid second line * Add Amsterdam link to README.md * Proper docs nav translation * Back to 300 font-weight except Chinese * fix docs build * Update Amsterdam link * remove symlinks * more zh punctuation * apply lost comment by @zhang2014 * Apply comments by @zhang2014 from #3417 * Remove Beijing link * rm incorrect symlink * restore content of docs/zh/operations/table_engines/index.md * CLICKHOUSE-3751: stem terms while searching docs * CLICKHOUSE-3751: use English stemmer in non-English docs too * CLICKHOUSE-4135 fix * Remove past meetup link * Add blog link to top nav * Add ContentSquare article link * Add form link to front page + refactor some texts * couple markup fixes * minor * Introduce basic ODBC driver page in docs * More verbose 3rd party libs disclaimer * Put third-party stuff into a separate folder * Separate third-party stuff in ToC too * Update links * Move stuff that is not really (only) a client library into a separate page * Add clickhouse-hdfs-loader link * Some introduction for "interfaces" section * Rewrite tcp.md * http_interface.md -> http.md * fix link * Remove unconvenient error for now * try to guess anchor instead of failing * remove symlink * Remove outdated info from introduction * remove ru roadmap.md * replace ru roadmap.md with symlink * Update roadmap.md * lost file * Title case in toc_en.yml * Sync "Functions" ToC section with en * Remove reference to pretty old ClickHouse release from docs * couple lost symlinks in fa * Close quote in proper place * Rewrite en/getting_started/index.md * Sync en<>ru getting_started/index.md * minor changes * Some gui.md refactoring * Translate DataGrip section to ru * Translate DataGrip section to zh * Translate DataGrip section to fa * Translate DBeaver section to fa * Translate DBeaver section to zh * Split third-party GUI to open-source and commercial * Mention some RDBMS integrations + ad-hoc translation fixes * Add rel="external nofollow" to outgoing links from docs * Lost blank lines * Fix class name * More rel="external nofollow" * Apply suggestions by @sundy-li * Mobile version of front page improvements * test * test 2 * test 3 * Update LICENSE * minor docs fix * Highlight current article as suggested by @sundy-li * fix link destination * Introduce backup.md (only "en" for now) * Mention INSERT+SELECT in backup.md * Some improvements for replication.md * Add backup.md to toc * Mention clickhouse-backup tool * Mention LightHouse in third-party GUI list * Introduce interfaces/third-party/proxy.md * Add clickhouse-bulk to proxy.md * Major extension of integrations.md contents * fix link target * remove unneeded file * better toc item name * fix markdown * better ru punctuation * Add yet another possible backup approach * Simplify copying permalinks to headers * Support non-eng link anchors in docs + update some deps * Generate anchors for single-page mode automatically * Remove anchors to top of pages * Remove anchors that nobody links to * build fixes * fix few links * restore css * fix some links * restore gifs * fix lost words * more docs fixes * docs fixes * NULL anchor * update urllib3 dependency * more fixes
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Структура ключа задаётся в элементе `<key>`. Поля ключа задаются в том же формате, что и [атрибуты](external_dicts_dict_structure.md) словаря. Пример:
```xml
<structure>
<key>
<attribute>
<name>field1</name>
<type>String</type>
</attribute>
<attribute>
<name>field2</name>
<type>UInt32</type>
</attribute>
...
</key>
...
```
При запросе в функции `dictGet*` в качестве ключа передаётся кортеж. Пример: `dictGetString('dict_name', 'attr_name', tuple('string for field1', num_for_field2))`.
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## Атрибуты {#ext_dict_structure-attributes}
Пример конфигурации:
```xml
<structure>
...
<attribute>
<name>Name</name>
<type>ClickHouseDataType</type>
<null_value></null_value>
<expression>rand64()</expression>
<hierarchical>true</hierarchical>
<injective>true</injective>
<is_object_id>true</is_object_id>
</attribute>
</structure>
```
Поля конфигурации:
| Тег | Описание | Обязательный |
| ---- | ------------- | --------- |
| `name` | Имя столбца. | Да |
| `type` | Тип данных ClickHouse.<br/>ClickHouse пытается привести значение из словаря к заданному типу данных. Например, в случае MySQL, в таблице-источнике поле может быть `TEXT`, `VARCHAR`, `BLOB`, но загружено может быть как `String`. [Nullable](../../data_types/nullable.md) не поддерживается. | Да |
| `null_value` | Значение по умолчанию для несуществующего элемента.<br/>В примере это пустая строка. Нельзя указать значение `NULL`. | Да |
| `expression` | [Выражение](../syntax.md#syntax-expressions), которое ClickHouse выполняет со значением.<br/>Выражением может быть имя столбца в удаленной SQL базе. Таким образом, вы можете использовать его для создания псевдонима удаленного столбца.<br/><br/>Значение по умолчанию: нет выражения. | Нет |
| `hierarchical` | Поддержка иерархии. Отображение в идентификатор родителя.<br/><br/>Значение по умолчанию: `false`. | Нет |
| `injective` | Признак [инъективности](https://ru.wikipedia.org/wiki/Инъекция_(математика)) отображения `id -> attribute`. <br/>Если `true`, то обращения к словарям с включенной инъективностью могут быть автоматически переставлены ClickHouse за стадию `GROUP BY`, что как правило существенно сокращает их количество.<br/><br/>Значение по умолчанию: `false`. | Нет |
| `is_object_id` | Признак того, что запрос выполняется к документу MongoDB по `ObjectID`.<br/><br/>Значение по умолчанию: `false`. | Нет |
[Оригинальная статья](https://clickhouse.yandex/docs/ru/query_language/dicts/external_dicts_dict_structure/) <!--hide-->