add system variable tidb_opt_range_max_size (#11239) (#11921)

* add system variable tidb_opt_range_mem_quota * add example * fix code format * fix more code format * Update system-variables.md Co-authored-by: shichun-0415 <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * upd example * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md Co-authored-by: TomShawn <[email protected]> * Update system-variables.md * add toggle display * Update system-variables.md * Update system-variables.md Co-authored-by: xuyifan <[email protected]> Co-authored-by: shichun-0415 <[email protected]> Co-authored-by: Yifan Xu <[email protected]> Co-authored-by: shichun-0415 <[email protected]> Co-authored-by: TomShawn <[email protected]>
pingcap · Nov 8, 2022 · 13e8cb0 · 13e8cb0
1 parent 60fc57d
commit 13e8cb0
Showing 1 changed file with 13 additions and 0 deletions.
diff --git a/system-variables.md b/system-variables.md
@@ -2392,6 +2392,19 @@ explain select * from t where age=5;
 - 默认值：`OFF`
 - 指定是否允许优化器将 `Projection` 算子下推到 TiKV 或者 TiFlash。
 
+### `tidb_opt_range_max_size`
+
+> **警告：**
+>
+> 当前版本中该变量控制的功能尚未完全生效，请保留默认值。
+
+- 作用域：SESSION | GLOBAL
+- 是否持久化到集群：是
+- 默认值：`0`
+- 取值范围：`[0, 9223372036854775807]`
+- 单位：字节
+- 该变量用于指定优化器构造扫描范围的内存用量上限。当该变量为 `0` 时，表示对扫描范围没有内存限制。如果构造精确的扫描范围会超出内存用量限制，优化器会使用更宽松的扫描范围（例如 `[[NULL,+inf]]`）。如果执行计划中未使用精确的扫描范围，可以调大该变量的值让优化器构造精确的扫描范围。
+
 ### `tidb_opt_scan_factor`
 
 - 作用域：SESSION | GLOBAL