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Co-authored-by: tavplubix <tavplubix@gmail.com>
Co-authored-by: BayoNet <da-daos@yandex.ru>
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docs/en/engines/database-engines/materialize-mysql.md
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@ -13,22 +13,22 @@ toc_title: MaterializeMySQL
``` sql
CREATE DATABASE [IF NOT EXISTS] db_name [ON CLUSTER cluster]
ENGINE = MaterializeMySQL('host:port', ['database' | database], 'user', 'password')
ENGINE = MaterializeMySQL('host:port', ['database' | database], 'user', 'password') [SETTINGS ...]
```
**Engine Parameters**
- `host:port` — MySQL server address.
- `host:port` — MySQL server endpoint.
- `database` — Remote database name.
- `user` — MySQL user.
- `password` — User password.
## Virtual columns {#virtual-columns}
When working with the MaterializeMySQL database engine, [ReplacingMergeTree](../../engines/table-engines/mergetree-family/replacingmergetree.md) tables are used with virtual `_sign` and `_version` columns.
When working with the `MaterializeMySQL` database engine, [ReplacingMergeTree](../../engines/table-engines/mergetree-family/replacingmergetree.md) tables are used with virtual `_sign` and `_version` columns.
- `_version` — Works as transaction counter. Type [UInt64](../../sql-reference/data-types/int-uint.md).
- `_sign` — Works as deletion mark. Type [Int8](../../sql-reference/data-types/int-uint.md). Possible values:
- `_version` — Transaction counter. Type [UInt64](../../sql-reference/data-types/int-uint.md).
- `_sign` — Deletion mark. Type [Int8](../../sql-reference/data-types/int-uint.md). Possible values:
- `1` — Row is not deleted,
- `-1` — Row is deleted.
@ -55,7 +55,7 @@ All other MySQL data types are converted into [String](../../sql-reference/data-
[Nullable](../../sql-reference/data-types/nullable.md) is supported.
## Specifics and recommendations {#specifics-and-recommendations}
## Specifics and Recommendations {#specifics-and-recommendations}
### DDL Queries
@ -63,7 +63,7 @@ MySQL DDL queries are converted into the corresponding ClickHouse [ALTER](../../
### DML Queries
MaterializeMySQL engine performs only `INSERT` and `SELECT` queries.
`MaterializeMySQL` engine supports only `INSERT` and `SELECT` queries.
MySql `DELETE` query is converted into `INSERT` with `_sign=-1`.
@ -84,7 +84,7 @@ ClickHouse has only one physical order, which is determined by `ORDER BY` clause
**Notes**
- Rows with `_sign=-1` are not deleted physically from the tables.
- Cascade UPDATE/DELETE queries are not supported by MaterializeMySQL engine.
- Cascade `UPDATE/DELETE` queries are not supported by the `MaterializeMySQL` engine.
- Replication can be easily broken.
- Manual operations on database and tables are forbidden.