Add TABLE OVERRIDE docs

docs/en/engines/database-engines/materialized-mysql.md

@@ -17,6 +17,7 @@ ClickHouse server works as MySQL replica. It reads binlog and performs DDL and D
 ``` sql
 CREATE DATABASE [IF NOT EXISTS] db_name [ON CLUSTER cluster]
 ENGINE = MaterializedMySQL('host:port', ['database' | database], 'user', 'password') [SETTINGS ...]
+[TABLE OVERRIDE table1 (...), TABLE OVERRIDE table2 (...)]
 ```
 
 **Engine Parameters**
@@ -109,15 +110,19 @@ MySQL DDL queries are converted into the corresponding ClickHouse DDL queries ([
 
 - MySQL `DELETE` query is converted into `INSERT` with `_sign=-1`.
 
-- MySQL `UPDATE` query is converted into `INSERT` with `_sign=-1` and `INSERT` with `_sign=1`.
+- MySQL `UPDATE` query is converted into `INSERT` with `_sign=-1` and `INSERT` with `_sign=1` if the primary key has been changed, or
+  `INSERT` with `_sign=1` if not.
 
 ### Selecting from MaterializedMySQL Tables {#select}
 
 `SELECT` query from `MaterializedMySQL` tables has some specifics:
 
-- If `_version` is not specified in the `SELECT` query, [FINAL](../../sql-reference/statements/select/from.md#select-from-final) modifier is used. So only rows with `MAX(_version)` are selected.
+- If `_version` is not specified in the `SELECT` query, the
+  [FINAL](../../sql-reference/statements/select/from.md#select-from-final) modifier is used, so only rows with
+  `MAX(_version)` are returned for each primary key value.
 
-- If `_sign` is not specified in the `SELECT` query, `WHERE _sign=1` is used by default. So the deleted rows are not included into the result set.
+- If `_sign` is not specified in the `SELECT` query, `WHERE _sign=1` is used by default. So the deleted rows are not
+  included into the result set.
 
 - The result includes columns comments in case they exist in MySQL database tables.
 
@@ -125,15 +130,69 @@ MySQL DDL queries are converted into the corresponding ClickHouse DDL queries ([
 
 MySQL `PRIMARY KEY` and `INDEX` clauses are converted into `ORDER BY` tuples in ClickHouse tables.
 
-ClickHouse has only one physical order, which is determined by `ORDER BY` clause. To create a new physical order, use [materialized views](../../sql-reference/statements/create/view.md#materialized).
+ClickHouse has only one physical order, which is determined by `ORDER BY` clause. To create a new physical order, use
+[materialized views](../../sql-reference/statements/create/view.md#materialized).
 
 **Notes**
 
 - Rows with `_sign=-1` are not deleted physically from the tables.
-- Cascade `UPDATE/DELETE` queries are not supported by the `MaterializedMySQL` engine.
+- Cascade `UPDATE/DELETE` queries are not supported by the `MaterializedMySQL` engine, as they are not visible in the
+  MySQL binlog.
 - Replication can be easily broken.
 - Manual operations on database and tables are forbidden.
-- `MaterializedMySQL` is influenced by [optimize_on_insert](../../operations/settings/settings.md#optimize-on-insert) setting. The data is merged in the corresponding table in the `MaterializedMySQL` database when a table in the MySQL server changes.
+- `MaterializedMySQL` is affected by the [optimize_on_insert](../../operations/settings/settings.md#optimize-on-insert)
+  setting. Data is merged in the corresponding table in the `MaterializedMySQL` database when a table in the MySQL
+  server changes.
+
+### Table Overrides {#table-overrides}
+
+Table overrides can be used to customize the ClickHouse DDL queries, allowing you to make schema optimizations for your
+application. This is especially useful for controlling partitioning, which is important for the overall performance of
+MaterializedMySQL.
+
+```sql
+CREATE DATABASE db_name ENGINE = MaterializedMySQL(...)
+[SETTINGS ...]
+[TABLE OVERRIDE table_name (
+    [COLUMNS (
+        [name1 [type1] [DEFAULT|MATERIALIZED|ALIAS expr1] [TTL expr1], ...]
+        [INDEX index_name1 expr1 TYPE type1(...) GRANULARITY value1, ...]
+        [PROJECTION projection_name_1 (SELECT <COLUMN LIST EXPR> [GROUP BY] [ORDER BY]), ...]
+	)]
+	[ORDER BY expr]
+	[PRIMARY KEY expr]
+	[PARTITION BY expr]
+	[SAMPLE BY expr]
+	[TTL expr]
+), ...]
+```
+
+Example:
+
+```sql
+CREATE DATABASE db_name ENGINE = MaterializedMySQL(...)
+TABLE OVERRIDE table1 (
+    COLUMNS (
+	    userid UUID,
+	    category LowCardinality(String),
+		timestamp DateTime CODEC(Delta, Default)
+    )
+    PARTITION BY toYear(timestamp)
+),
+TABLE OVERRIDE table2 (
+    COLUMNS (
+	    ip_hash UInt32 MATERIALIZED xxHash32(client_ip),
+		client_ip String TTL created + INTERVAL 72 HOUR
+	)
+	SAMPLE BY ip_hash
+)
+```
+
+The `COLUMNS` list is sparse; it contains only modified or extra (MATERIALIZED or ALIAS) columns. Modified columns with
+a different type must be assignable from the original type. There is currently no validation of this or similar issues
+when the `CREATE DATABASE` query executes, so extra care needs to be taken.
+
+You may specify overrides for tables that do not exist yet.
 
 ## Examples of Use {#examples-of-use}