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- 问题分类：更新不及时、描述错误、代码错误、参数错误、链接错误、错别字
- 出现的页面：链接+截图
- 出现的错误：
系统变量页面增加了【是否受 Hint SET_VAR 控制】说明项，但有些参数的标记有误，请确认。
https://docs.pingcap.com/zh/tidb/v7.4/system-variables#tidb_enable_new_cost_interface-从-v620-版本开始引入
tidb_enable_new_cost_interface
是否受 Hint SET_VAR 控制：是 → 否
mysql> select /*+ set_var(tidb_enable_new_cost_interface=1) */ @@tidb_enable_new_cost_interface;
+----------------------------------+
| @@tidb_enable_new_cost_interface |
+----------------------------------+
| 1 |
+----------------------------------+
1 row in set, 1 warning (0.00 sec)
Warning (Code 3637): Variable 'tidb_enable_new_cost_interface' might not be affected by SET_VAR hint.
https://docs.pingcap.com/zh/tidb/v7.4/system-variables#tidb_last_ddl_info-从-v600-版本开始引入
tidb_last_ddl_info
是否受 Hint SET_VAR 控制：是 → 否
mysql> select /*+ set_var(tidb_last_ddl_info=1) */ @@tidb_last_ddl_info;
+--------------------------+
| @@tidb_last_ddl_info |
+--------------------------+
| {"query":"","seq_num":0} |
+--------------------------+
1 row in set, 2 warnings (0.00 sec)
Warning (Code 3637): Variable 'tidb_last_ddl_info' might not be affected by SET_VAR hint.
Warning (Code 1238): Variable 'tidb_last_ddl_info' is a read only variable
https://docs.pingcap.com/zh/tidb/v7.4/system-variables#tidb_isolation_read_engines-从-v40-版本开始引入
tidb_isolation_read_engines
是否受 Hint SET_VAR 控制：否 → 是
mysql> select /*+ set_var(tidb_isolation_read_engines=tikv) */ @@tidb_isolation_read_engines;
+-------------------------------+
| @@tidb_isolation_read_engines |
+-------------------------------+
| tikv |
+-------------------------------+
1 row in set (0.00 sec)
是否受 Hint SET_VAR 控制：否 → 是
mpp_exchange_compression_mode
tidb_allow_fallback_to_tikv
tiflash_fastscan
tiflash_fine_grained_shuffle_stream_count
tiflash_fine_grained_shuffle_batch_size
这几个参数的相关pr
https://github.com/pingcap/tidb/pull/47258
planner: change SET_VAR behavior for non-verified vars and add some var #47258
https://github.com/pingcap/tidb/pull/47609
sessionctx: fix var typo #47609