From 12c8658c85ecef9b1b4a3bdaead1d2df62c46185 Mon Sep 17 00:00:00 2001
From: Chao Wang <cclcwangchao@hotmail.com>
Date: Thu, 26 Sep 2024 05:39:24 +0800
Subject: [PATCH] make test stable

---
 pkg/expression/exprstatic/evalctx.go | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/pkg/expression/exprstatic/evalctx.go b/pkg/expression/exprstatic/evalctx.go
index 06cf461f0fa7a..5086143497a1c 100644
--- a/pkg/expression/exprstatic/evalctx.go
+++ b/pkg/expression/exprstatic/evalctx.go
@@ -496,11 +496,35 @@ func (ctx *EvalContext) currentTimeFuncFromStringVal(val string) func() (time.Ti
 
 func newSessionVarsWithSystemVariables(vars map[string]string) (*variable.SessionVars, error) {
 	sessionVars := variable.NewSessionVars(nil)
+	var cs, col []string
 	for name, val := range vars {
-		if err := sessionVars.SetSystemVar(name, val); err != nil {
+		switch strings.ToLower(name) {
+		// `charset_connection` and `collation_connection` will overwrite each other.
+		// To make the result more determinate, just set them at last step in order:
+		// `charset_connection` first, then `collation_connection`.
+		case variable.CharacterSetConnection:
+			cs = []string{name, val}
+		case variable.CollationConnection:
+			col = []string{name, val}
+		default:
+			if err := sessionVars.SetSystemVar(name, val); err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	if cs != nil {
+		if err := sessionVars.SetSystemVar(cs[0], cs[1]); err != nil {
 			return nil, err
 		}
 	}
+
+	if col != nil {
+		if err := sessionVars.SetSystemVar(col[0], col[1]); err != nil {
+			return nil, err
+		}
+	}
+
 	return sessionVars, nil
 }