Skip to content

release-8.5: optimizer: update default value of fix control 52869 #23142

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
time-and-fate wants to merge 2 commits into
base: release-8.5
Choose a base branch
from
+1 −1
Open

release-8.5: optimizer: update default value of fix control 52869 #23142

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
5db9fd8
update optimizer fix control 52869 default value
time-and-fate Jun 24, 2026
7bf65ff
Update optimizer-fix-controls.md
qiancai Jun 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
2 changes: 1 addition & 1 deletion optimizer-fix-controls.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@ SET SESSION tidb_opt_fix_control = '44262:ON,44389:ON';

### [`52869`](https://github.com/pingcap/tidb/issues/52869) <span class="version-mark">New in v8.1.0</span>

- Default value: `OFF`
- Default value: `ON`. Before v8.5.7, the default value is `OFF`.
- Possible values: `ON`, `OFF`
- As stated in the **Note** of [Explain Statements Using Index Merge](/explain-index-merge.md#examples), if the optimizer can choose the single index scan method (other than full table scan) for a query plan, the optimizer will not automatically use index merge.
- You can remove this limitation by enabling this fix control. Removing this limitation enables the optimizer to choose index merge automatically in more queries, but might cause the optimizer to ignore the optimal execution plans. Therefore, it is recommended to conduct sufficient tests on actual use cases before removing this limitation to make sure that it will not cause performance regressions.
Expand Down
Loading