*: update doc for generated columns GA (pingcap#13246)

develop/dev-guide-create-table.md

@@ -57,7 +57,7 @@ Column definitions typically take the following form.
 
 - `{column_name}`: The column name.
 - `{data_type}`: The column [data type](/data-type-overview.md).
-- `{column_qualification}`: Column qualifications, such as **column-level constraints** or [generated column (experimental feature)](/generated-columns.md) clauses.
+- `{column_qualification}`: Column qualifications, such as **column-level constraints** or [generated column](/generated-columns.md) clauses.
 
 You can add some columns to the `users` table, such as the unique identifier `id`, `balance` and `nickname`.
 
@@ -102,7 +102,7 @@ A [primary key](/constraints.md#primary-key) is a column or a set of columns in
 
 > **Note:**
 >
-> The default definition of **primary key** in TiDB is different from that in [InnoDB](https://mariadb.com/kb/en/innodb/)(the common storage engine of MySQL). 
+> The default definition of **primary key** in TiDB is different from that in [InnoDB](https://dev.mysql.com/doc/refman/8.0/en/innodb-storage-engine.html)(the common storage engine of MySQL).
 >
 > - In **InnoDB**: A **primary key** is unique, not null, and **index clustered**.
 >

develop/dev-guide-schema-design-overview.md

@@ -27,7 +27,7 @@ TiDB comes with a default database named `test`. However, it is recommended that
 
 A table is a collection of related data in a [database](#database).
 
-Each table consists of **rows** and **columns**. Each value in a row belongs to a specific **column**. Each column allows only a single data type. To further qualify columns, you can add some [constraints](/constraints.md). To accelerate calculations, you can add [generated columns (experimental feature)](/generated-columns.md).
+Each table consists of **rows** and **columns**. Each value in a row belongs to a specific **column**. Each column allows only a single data type. To further qualify columns, you can add some [constraints](/constraints.md). To accelerate calculations, you can add [generated columns](/generated-columns.md).
 
 ### Index
 
@@ -40,7 +40,7 @@ There are two common types of indexes:
 
 > **Note:**
 >
-> In TiDB, the default definition of **Primary Key** is different from that in [InnoDB](https://mariadb.com/kb/en/innodb/) (a common storage engine of MySQL).
+> In TiDB, the default definition of **Primary Key** is different from that in [InnoDB](https://dev.mysql.com/doc/refman/8.0/en/innodb-storage-engine.html) (a common storage engine of MySQL).
 >
 > - In InnoDB, the definition of **Primary Key** is unique, not null, and a **clustered index**.
 > - In TiDB, the definition of **Primary Key** is unique and not null. But the primary key is not guaranteed to be a **clustered index**. To specify whether the primary key is a clustered index, you can add non-reserved keywords `CLUSTERED` or `NONCLUSTERED` after `PRIMARY KEY` in a `CREATE TABLE` statement. If a statement does not explicitly specify these keywords, the default behavior is controlled by the system variable `@@global.tidb_enable_clustered_index`. For more information, see [Clustered Indexes](/clustered-indexes.md).

generated-columns.md

@@ -6,10 +6,6 @@ aliases: ['/docs/dev/generated-columns/','/docs/dev/reference/sql/generated-colu
 
 # Generated Columns
 
-> **Warning:**
->
-> This is still an experimental feature. It is **NOT** recommended that you use it in the production environment.
-
 This document introduces the concept and usage of generated columns.
 
 ## Basic concepts

time-to-live.md

@@ -100,7 +100,7 @@ You can use TTL together with [default values of the data types](/data-type-defa
 
 ### TTL and generated columns
 
-You can use TTL together with [generated columns](/generated-columns.md) (experimental feature) to configure complex expiration rules. For example:
+You can use TTL together with [generated columns](/generated-columns.md) to configure complex expiration rules. For example:
 
 ```sql
 CREATE TABLE message (
@@ -252,7 +252,7 @@ Currently, the TTL feature has the following limitations:
 * A table with the TTL attribute does not support being referenced by other tables as the primary table in a foreign key constraint.
 * It is not guaranteed that all expired data is deleted immediately. The time when expired data is deleted depends on the scheduling interval and scheduling window of the background cleanup job.
 * For tables that use [clustered indexes](/clustered-indexes.md), if the primary key is neither an integer nor a binary string type, the TTL job cannot be split into multiple tasks. This will cause the TTL job to be executed sequentially on a single TiDB node. If the table contains a large amount of data, the execution of the TTL job might become slow.
-* TTL is not available for [TiDB Cloud Serverless Tier](https://docs.pingcap.com/tidbcloud/select-cluster-tier#serverless-tier-beta). 
+* TTL is not available for [TiDB Cloud Serverless Tier](https://docs.pingcap.com/tidbcloud/select-cluster-tier#serverless-tier-beta).
 
 ## FAQs