From 5db9fd8f97073e455964cb56a40957366f2b6753 Mon Sep 17 00:00:00 2001
From: time-and-fate <25057648+time-and-fate@users.noreply.github.com>
Date: Thu, 25 Jun 2026 01:35:53 +0800
Subject: [PATCH 1/2] update optimizer fix control 52869 default value
---
optimizer-fix-controls.md | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/optimizer-fix-controls.md b/optimizer-fix-controls.md
index b75d1033235be..9382625886f0e 100644
--- a/optimizer-fix-controls.md
+++ b/optimizer-fix-controls.md
@@ -103,7 +103,7 @@ SET SESSION tidb_opt_fix_control = '44262:ON,44389:ON';
### [`52869`](https://github.com/pingcap/tidb/issues/52869) New in v8.1.0
-- Default value: `OFF`
+- Default value: `ON`. Before v8.5.7, the default value is `OFF`; starting from v8.5.7, it is `ON`.
- 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.
From 7bf65ff4c972746c909dbc832d8e19adf7074a2e Mon Sep 17 00:00:00 2001
From: Grace Cai
Date: Thu, 25 Jun 2026 15:50:30 +0800
Subject: [PATCH 2/2] Update optimizer-fix-controls.md
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
---
optimizer-fix-controls.md | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/optimizer-fix-controls.md b/optimizer-fix-controls.md
index 9382625886f0e..dbe7e9126885d 100644
--- a/optimizer-fix-controls.md
+++ b/optimizer-fix-controls.md
@@ -103,7 +103,7 @@ SET SESSION tidb_opt_fix_control = '44262:ON,44389:ON';
### [`52869`](https://github.com/pingcap/tidb/issues/52869) New in v8.1.0
-- Default value: `ON`. Before v8.5.7, the default value is `OFF`; starting from v8.5.7, it is `ON`.
+- 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.