From b08f6be9c07e2c90d0082b6b0ff81f0f2c4c2241 Mon Sep 17 00:00:00 2001
From: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
Date: Wed, 27 Jan 2021 10:34:23 +0800
Subject: [PATCH] expression: do not rewrite `like` to `=` if new collation is
 enabled (#21893) (#22531)

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
---
 planner/core/expression_rewriter.go | 4 ++--
 util/ranger/ranger_test.go          | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/planner/core/expression_rewriter.go b/planner/core/expression_rewriter.go
index f4f98ef224246..4b548211a6c6b 100644
--- a/planner/core/expression_rewriter.go
+++ b/planner/core/expression_rewriter.go
@@ -1449,8 +1449,8 @@ func (er *expressionRewriter) patternLikeToExpression(v *ast.PatternLikeExpr) {
 	var function expression.Expression
 	fieldType := &types.FieldType{}
 	isPatternExactMatch := false
-	// Treat predicate 'like' the same way as predicate '=' when it is an exact match.
-	if patExpression, ok := er.ctxStack[l-1].(*expression.Constant); ok {
+	// Treat predicate 'like' the same way as predicate '=' when it is an exact match and new collation is not enabled.
+	if patExpression, ok := er.ctxStack[l-1].(*expression.Constant); ok && !collate.NewCollationEnabled() {
 		patString, isNull, err := patExpression.EvalString(nil, chunk.Row{})
 		if err != nil {
 			er.err = err
diff --git a/util/ranger/ranger_test.go b/util/ranger/ranger_test.go
index 626963428ece5..db59755f59730 100644
--- a/util/ranger/ranger_test.go
+++ b/util/ranger/ranger_test.go
@@ -384,14 +384,14 @@ create table t(
 		{
 			indexPos:    0,
 			exprStr:     "a LIKE 'abc'",
-			accessConds: "[eq(test.t.a, abc)]",
+			accessConds: "[like(test.t.a, abc, 92)]",
 			filterConds: "[]",
 			resultStr:   "[[\"abc\",\"abc\"]]",
 		},
 		{
 			indexPos:    0,
 			exprStr:     `a LIKE "ab\_c"`,
-			accessConds: "[eq(test.t.a, ab_c)]",
+			accessConds: "[like(test.t.a, ab\\_c, 92)]",
 			filterConds: "[]",
 			resultStr:   "[[\"ab_c\",\"ab_c\"]]",
 		},
@@ -405,14 +405,14 @@ create table t(
 		{
 			indexPos:    0,
 			exprStr:     `a LIKE '\%a'`,
-			accessConds: "[eq(test.t.a, %a)]",
+			accessConds: "[like(test.t.a, \\%a, 92)]",
 			filterConds: "[]",
 			resultStr:   `[["%a","%a"]]`,
 		},
 		{
 			indexPos:    0,
 			exprStr:     `a LIKE "\\"`,
-			accessConds: "[eq(test.t.a, \\)]",
+			accessConds: "[like(test.t.a, \\, 92)]",
 			filterConds: "[]",
 			resultStr:   "[[\"\\\",\"\\\"]]",
 		},