Skip to content

add doc for tidb_opt_index_join_max_scan_rows_ratio #21629

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
guo-shaoge wants to merge 4 commits into
base: master
Choose a base branch
from
+10 −0
Open

add doc for tidb_opt_index_join_max_scan_rows_ratio #21629

Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
7becbd0
add doc for tidb_opt_index_join_max_scan_rows_ratio
guo-shaoge May 12, 2026
7ea074e
Apply suggestion from @qiancai
guo-shaoge May 25, 2026
0566047
Revert "Apply suggestion from @qiancai"
guo-shaoge May 25, 2026
7769cd5
update
guo-shaoge May 25, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 10 additions & 0 deletions system-variables.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3734,6 +3734,16 @@ v5.0 后，用户仍可以单独修改以上系统变量（会有废弃警告）
- 默认值：`1.5`
- 表示 TiDB 往临时磁盘读写一个字节数据的 I/O 开销。该变量是[代价模型](/cost-model.md)内部使用的变量，**不建议**修改该变量的值。

### `tidb_opt_index_join_max_scan_rows_ratio` <span class="version-mark">从 v9.0.0 版本开始引入</span>

- 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
- 类型：浮点数
- 范围：`[0, 18446744073709551615]`
- 默认值：`0`
- 控制优化器在处理 Join 查询时限制选择 IndexJoin 算子的阈值。优化器会估算 IndexJoin 和 HashJoin 分别需要扫描的行数，并计算 IndexJoin 要扫描的行数与 HashJoin 要扫描的行数的比值。如果该比值大于或等于该变量的值，优化器会避免选择 IndexJoin。默认值 `0` 表示关闭该限制。

### `tidb_opt_distinct_agg_push_down`

- 作用域：SESSION
Expand Down
Loading