cloud: enabling ttl table in serverless (pingcap#17676) (pingcap#17769)…

… (pingcap#17771)

mysql-schema.md

@@ -69,10 +69,6 @@ Currently, the `help_topic` is NULL.
 
 ## TTL related system tables
 
-> **Note:**
-
-> The TTL related system tables are not available on [TiDB Serverless](https://docs.pingcap.com/tidbcloud/select-cluster-tier#tidb-serverless) clusters.
-
 * `tidb_ttl_table_status`: the previously executed TTL job and ongoing TTL job for all TTL tables
 * `tidb_ttl_task`: the current ongoing TTL subtasks
 * `tidb_ttl_job_history`: the execution history of TTL tasks in the last 90 days

time-to-live.md

@@ -258,7 +258,6 @@ 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 Serverless](https://docs.pingcap.com/tidbcloud/select-cluster-tier#tidb-serverless).
 
 ## FAQs