planner: add tidb_enable_binding_usage

system-variables.md

@@ -1937,6 +1937,15 @@ mysql> SELECT job_info FROM mysql.analyze_jobs ORDER BY end_time DESC LIMIT 1;
 - Default value: `OFF`
 - This variable controls whether to enable the deprecated batch-dml feature. When it is enabled, certain statements might be split into multiple transactions, which is non-atomic and should be used with care. When using batch-dml, you must ensure that there are no concurrent operations on the data you are operating on. To make it work, you must also specify a positive value for `tidb_batch_dml_size` and enable at least one of `tidb_batch_insert` and `tidb_batch_delete`.
 
+### tidb_enable_binding_usage <span class="version-mark">New in v9.0.0</span>
+
+- Scope: GLOBAL
+- Persists to cluster: Yes
+- Applies to hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value): No
+- Type: Boolean
+- Default value: `ON`
+- This variable is used to control whether to enable the usage statistics collection for SQL plan bindings. Every six hours, the usage of bindinfo will be written into TiKV.
+
 ### tidb_enable_cascades_planner
 
 > **Warning:**