Add docs for lightweight deletes

docs/en/sql-reference/statements/alter/delete.md

@@ -12,7 +12,11 @@ ALTER TABLE [db.]table [ON CLUSTER cluster] DELETE WHERE filter_expr
 
 Deletes data matching the specified filtering expression. Implemented as a [mutation](../../../sql-reference/statements/alter/index.md#mutations).
 
-:::note    
+:::info
+The `ALTER TABLE` command is considered a heavyweight operation that requires the underlying data to be merged before it is deleted. For MergeTree tables, consider using the [`DELETE FROM` query](../delete.md), which performs a lightweight delete and can be considerably faster.
+:::
+
+:::note
 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.
 :::
 

docs/en/sql-reference/statements/delete.md

@@ -0,0 +1,36 @@
+---
+slug: /en/sql-reference/statements/delete
+sidebar_position: 36
+sidebar_label: DELETE
+---
+
+# DELETE Statement
+
+``` sql
+DELETE FROM [db.]table [WHERE expr]
+```
+
+For MergeTree tables, `DELETE FROM` performs a lightweight delete on the given table, which means that the deleted rows are marked as deleted immediately and deleted rows will be filtered out of all subsequent queries. The underlying data is permanently deleted whenever merges occur.
+
+For example, the following query deletes all rows from the `hits` table where the `Title` column contains the text `hello`:
+
+```sql
+DELETE FROM hits WHERE Title LIKE '%hello%';
+```
+
+
+:::note
+This feature is experimental and requires you to set `allow_experimental_lightweight_delete` to true:
+
+```sql
+SET allow_experimental_lightweight_delete = true;
+```
+
+:::
+
+The [traditional way to delete rows](./alter/delete.md) in ClickHouse was to use `ALTER TABLE ... DELETE`, which is still a valid method for deleting rows. However, in most use cases the new lightweight `DELETE FROM` behavior will be considerably faster.
+
+:::info
+Lightweight deletes are asynchronous by default. Set `mutations_sync` equal to 1 to wait for one replica to process the statement, and set `mutations_sync` to 2 to wait for all replicas.
+:::
+