From f4b775445191e1b9bb31801e4170f92723a9a9f9 Mon Sep 17 00:00:00 2001
From: toutdesuite <guizhiluo2014@163.com>
Date: Thu, 9 Apr 2020 19:56:44 +0800
Subject: [PATCH] reference/performance: specify index name of primary key for
 USE_INDEX_MERGE (#2221)

---
 reference/performance/optimizer-hints.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/reference/performance/optimizer-hints.md b/reference/performance/optimizer-hints.md
index a501d9b2536dd..f75b4399e0a50 100644
--- a/reference/performance/optimizer-hints.md
+++ b/reference/performance/optimizer-hints.md
@@ -190,6 +190,10 @@ The `USE_INDEX_MERGE(t1_name, idx1_name [, idx2_name ...])` hint tells the optim
 select /*+ USE_INDEX_MERGE(t1, idx_a, idx_b, idx_c) */ * from t t1 where t1.a > 10 or t1.b > 10;
 ```
 
+> **Note:**
+>
+> The parameters of `USE_INDEX_MERGE` refer to index names, rather than column names. The index name of the primary key is `primary`.
+
 ### NO_INDEX_MERGE()
 
 The `NO_INDEX_MERGE()` hint disables the index merge feature of the optimizer.