system-variable: add a warning message for tidb_partition_prune_mode variable

partitioned-table.md

@@ -2033,7 +2033,7 @@ mysql> create table t2 (id int, code int);
 Query OK, 0 rows affected (0.01 sec)
 
 mysql> set @@tidb_partition_prune_mode = 'static';
-Query OK, 0 rows affected (0.00 sec)
+Query OK, 0 rows affected, 1 warning (0.00 sec)
 
 mysql> explain select /*+ TIDB_INLJ(t1, t2) */ t1.* from t1, t2 where t2.code = 0 and t2.id = t1.id;
 +--------------------------------+----------+-----------+------------------------+------------------------------------------------+

system-variables.md

@@ -4174,6 +4174,10 @@ SHOW WARNINGS;
 
 ### `tidb_partition_prune_mode` <span class="version-mark">从 v5.1 版本开始引入</span>
 
+> **警告：**
+>
+> 从 v8.5.0 开始，将该变量设置为 `static` 或 `static-only` 时会产生警告。该变量将在未来版本中废弃。
+
 - 作用域：SESSION | GLOBAL
 - 是否持久化到集群：是
 - 是否受 Hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value) 控制：是

tiflash/use-tiflash-mpp-mode.md

@@ -132,7 +132,7 @@ Query OK, 0 rows affected (0.10 sec)
 mysql> ALTER table test.employees SET tiflash replica 1;
 Query OK, 0 rows affected (0.09 sec)
 mysql> SET tidb_partition_prune_mode=static;
-Query OK, 0 rows affected (0.00 sec)
+Query OK, 0 rows affected, 1 warning (0.00 sec)
 mysql> explain SELECT count(*) FROM test.employees;
 +----------------------------------+----------+-------------------+-------------------------------+-----------------------------------+
 | id                               | estRows  | task              | access object                 | operator info                     |