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DOCSUP-790: docs for mutations_sync setting (#12639)
* Docs in English. * Fixed links bug. * Update docs/en/sql-reference/statements/alter/delete.md Co-authored-by: Ivan Blinkov <github@blinkov.ru> * Translated into Russian. Anchors in links syncronized with English text. One minor change in English text to unify two similar descriptions. Co-authored-by: Olga Revyakina <revolg@yandex-team.ru> Co-authored-by: Ivan Blinkov <github@blinkov.ru>
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@ -1723,4 +1723,21 @@ SELECT * FROM a;
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+---+
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```
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## mutations_sync {#mutations_sync}
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Allows to execute `ALTER TABLE ... UPDATE|DELETE` queries ([mutations](../../sql-reference/statements/alter/index.md#mutations)) synchronously.
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Possible values:
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- 0 - Mutations execute asynchronously.
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- 1 - The query waits for all mutations to complete on the current server.
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- 2 - The query waits for all mutations to complete on all replicas (if they exist).
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Default value: `0`.
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**See Also**
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- [Synchronicity of ALTER Queries](../../sql-reference/statements/alter/index.md#synchronicity-of-alter-queries)
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- [Mutations](../../sql-reference/statements/alter/index.md#mutations)
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[Original article](https://clickhouse.tech/docs/en/operations/settings/settings/) <!-- hide -->
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@ -9,7 +9,7 @@ toc_title: DELETE
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ALTER TABLE [db.]table [ON CLUSTER cluster] DELETE WHERE filter_expr
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```
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Allows to asynchronously delete data matching the specified filtering expression. Implemented as a [mutation](../../../sql-reference/statements/index.md#mutations).
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Allows to delete data matching the specified filtering expression. Implemented as a [mutation](../../../sql-reference/statements/alter/index.md#mutations).
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!!! note "Note"
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The `ALTER TABLE` prefix makes this syntax different from most other systems supporting SQL. It is intended to signify that unlike similar queries in OLTP databases this is a heavy operation not designed for frequent use.
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@ -17,3 +17,11 @@ Allows to asynchronously delete data matching the specified filtering expression
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The `filter_expr` must be of type `UInt8`. The query deletes rows in the table for which this expression takes a non-zero value.
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One query can contain several commands separated by commas.
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The synchronicity of the query processing is defined by the [mutations_sync](../../../operations/settings/settings.md#mutations_sync) setting. By default, it is asynchronous.
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**See also**
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- [Mutations](../../../sql-reference/statements/alter/index.md#mutations)
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- [Synchronicity of ALTER Queries](../../../sql-reference/statements/alter/index.md#synchronicity-of-alter-queries)
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- [mutations_sync](../../../operations/settings/settings.md#mutations_sync) setting
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@ -27,12 +27,6 @@ While these `ALTER` settings modify entities related to role-based access contro
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- [ROW POLICY](../../../sql-reference/statements/alter/row-policy.md)
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- [SETTINGS PROFILE](../../../sql-reference/statements/alter/settings-profile.md)
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## Synchronicity of ALTER Queries {#synchronicity-of-alter-queries}
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For non-replicated tables, all `ALTER` queries are performed synchronously. For replicated tables, the query just adds instructions for the appropriate actions to `ZooKeeper`, and the actions themselves are performed as soon as possible. However, the query can wait for these actions to be completed on all the replicas.
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For `ALTER ... ATTACH|DETACH|DROP` queries, you can use the `replication_alter_partitions_sync` setting to set up waiting. Possible values: `0` – do not wait; `1` – only wait for own execution (default); `2` – wait for all.
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## Mutations {#mutations}
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`ALTER` queries that are intended to manipulate table data are implemented with a mechanism called “mutations”, most notably [ALTER TABLE … DELETE](../../../sql-reference/statements/alter/delete.md) and [ALTER TABLE … UPDATE](../../../sql-reference/statements/alter/update.md). They are asynchronous background processes similar to merges in [MergeTree](../../../engines/table-engines/mergetree-family/index.md) tables that to produce new “mutated” versions of parts.
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@ -45,4 +39,12 @@ A mutation query returns immediately after the mutation entry is added (in case
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Entries for finished mutations are not deleted right away (the number of preserved entries is determined by the `finished_mutations_to_keep` storage engine parameter). Older mutation entries are deleted.
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## Synchronicity of ALTER Queries {#synchronicity-of-alter-queries}
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For non-replicated tables, all `ALTER` queries are performed synchronously. For replicated tables, the query just adds instructions for the appropriate actions to `ZooKeeper`, and the actions themselves are performed as soon as possible. However, the query can wait for these actions to be completed on all the replicas.
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For `ALTER ... ATTACH|DETACH|DROP` queries, you can use the `replication_alter_partitions_sync` setting to set up waiting. Possible values: `0` – do not wait; `1` – only wait for own execution (default); `2` – wait for all.
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For `ALTER TABLE ... UPDATE|DELETE` queries the synchronicity is defined by the [mutations_sync](../../../operations/settings/settings.md#mutations_sync) setting.
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[Original article](https://clickhouse.tech/docs/en/query_language/alter/) <!--hide-->
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@ -9,7 +9,7 @@ toc_title: UPDATE
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ALTER TABLE [db.]table UPDATE column1 = expr1 [, ...] WHERE filter_expr
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```
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Allows to asynchronously manipulate data matching the specified filtering expression. Implemented as a [mutation](../../../sql-reference/statements/index.md#mutations).
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Allows to manipulate data matching the specified filtering expression. Implemented as a [mutation](../../../sql-reference/statements/alter/index.md#mutations).
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!!! note "Note"
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The `ALTER TABLE` prefix makes this syntax different from most other systems supporting SQL. It is intended to signify that unlike similar queries in OLTP databases this is a heavy operation not designed for frequent use.
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@ -17,3 +17,12 @@ Allows to asynchronously manipulate data matching the specified filtering expres
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The `filter_expr` must be of type `UInt8`. This query updates values of specified columns to the values of corresponding expressions in rows for which the `filter_expr` takes a non-zero value. Values are casted to the column type using the `CAST` operator. Updating columns that are used in the calculation of the primary or the partition key is not supported.
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One query can contain several commands separated by commas.
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The synchronicity of the query processing is defined by the [mutations_sync](../../../operations/settings/settings.md#mutations_sync) setting. By default, it is asynchronous.
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**See also**
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- [Mutations](../../../sql-reference/statements/alter/index.md#mutations)
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- [Synchronicity of ALTER Queries](../../../sql-reference/statements/alter/index.md#synchronicity-of-alter-queries)
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- [mutations_sync](../../../operations/settings/settings.md#mutations_sync) setting
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@ -1480,4 +1480,21 @@ SELECT idx, i FROM null_in WHERE i IN (1, NULL) SETTINGS transform_null_in = 1;
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- [min_insert_block_size_bytes](#min-insert-block-size-bytes)
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## mutations_sync {#mutations_sync}
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Позволяет выполнять запросы `ALTER TABLE ... UPDATE|DELETE` ([мутации](../../sql-reference/statements/alter.md#mutations)) синхронно.
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Возможные значения:
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- 0 - мутации выполняются асинхронно.
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- 1 - запрос ждет завершения всех мутаций на текущем сервере.
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- 2 - запрос ждет завершения всех мутаций на всех репликах (если они есть).
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Значение по умолчанию: `0`.
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**См. также**
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- [Синхронность запросов ALTER](../../sql-reference/statements/alter.md#synchronicity-of-alter-queries)
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- [Мутации](../../sql-reference/statements/alter.md#mutations)
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[Оригинальная статья](https://clickhouse.tech/docs/ru/operations/settings/settings/) <!--hide-->
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@ -461,14 +461,7 @@ OPTIMIZE TABLE table_not_partitioned PARTITION tuple() FINAL;
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ALTER TABLE table-name MODIFY TTL ttl-expression
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```
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### Синхронность запросов ALTER {#sinkhronnost-zaprosov-alter}
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Для нереплицируемых таблиц, все запросы `ALTER` выполняются синхронно. Для реплицируемых таблиц, запрос всего лишь добавляет инструкцию по соответствующим действиям в `ZooKeeper`, а сами действия осуществляются при первой возможности. Но при этом, запрос может ждать завершения выполнения этих действий на всех репликах.
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Для запросов `ALTER ... ATTACH|DETACH|DROP` можно настроить ожидание, с помощью настройки `replication_alter_partitions_sync`.
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Возможные значения: `0` - не ждать, `1` - ждать выполнения только у себя (по умолчанию), `2` - ждать всех.
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### Мутации {#alter-mutations}
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### Мутации {#mutations}
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Мутации - разновидность запроса ALTER, позволяющая изменять или удалять данные в таблице. В отличие от стандартных запросов `DELETE` и `UPDATE`, рассчитанных на точечное изменение данных, область применения мутаций - достаточно тяжёлые изменения, затрагивающие много строк в таблице. Поддержана для движков таблиц семейства `MergeTree`, в том числе для движков с репликацией.
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@ -504,6 +497,15 @@ ALTER TABLE [db.]table MATERIALIZE INDEX name IN PARTITION partition_name
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Записи о последних выполненных мутациях удаляются не сразу (количество сохраняемых мутаций определяется параметром движка таблиц `finished_mutations_to_keep`). Более старые записи удаляются.
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### Синхронность запросов ALTER {#synchronicity-of-alter-queries}
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Для нереплицируемых таблиц, все запросы `ALTER` выполняются синхронно. Для реплицируемых таблиц, запрос всего лишь добавляет инструкцию по соответствующим действиям в `ZooKeeper`, а сами действия осуществляются при первой возможности. Но при этом, запрос может ждать завершения выполнения этих действий на всех репликах.
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Для запросов `ALTER ... ATTACH|DETACH|DROP` можно настроить ожидание, с помощью настройки `replication_alter_partitions_sync`.
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Возможные значения: `0` - не ждать, `1` - ждать выполнения только у себя (по умолчанию), `2` - ждать всех.
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Для запросов `ALTER TABLE ... UPDATE|DELETE` синхронность выполнения определяется настройкой [mutations_sync](../../operations/settings/settings.md#mutations_sync).
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## ALTER USER {#alter-user-statement}
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Изменяет аккаунт пользователя ClickHouse.
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@ -212,7 +212,7 @@ KILL MUTATION [ON CLUSTER cluster]
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[FORMAT format]
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```
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Пытается остановить выполняющиеся в данные момент [мутации](alter.md#alter-mutations). Мутации для остановки выбираются из таблицы [`system.mutations`](../../operations/system-tables.md#system_tables-mutations) с помощью условия, указанного в секции `WHERE` запроса `KILL`.
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Пытается остановить выполняющиеся в данные момент [мутации](alter.md#mutations). Мутации для остановки выбираются из таблицы [`system.mutations`](../../operations/system-tables.md#system_tables-mutations) с помощью условия, указанного в секции `WHERE` запроса `KILL`.
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Тестовый вариант запроса (`TEST`) только проверяет права пользователя и выводит список запросов для остановки.
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