revert #15125

pkg/expression/expr_to_pb.go

@@ -284,20 +284,13 @@ func (pc PbConverter) scalarFuncToPBExpr(expr *ScalarFunction) *tipb.Expr {
 		}
 	}
 
-	// put collation information into the RetType enforcedly and push it down to TiKV/MockTiKV
-	tp := *expr.RetType
-	if collate.NewCollationEnabled() {
-		_, str1 := expr.CharsetAndCollation()
-		tp.SetCollate(str1)
-	}
-
 	// Construct expression ProtoBuf.
 	return &tipb.Expr{
 		Tp:        tipb.ExprType_ScalarFunc,
 		Val:       encoded,
 		Sig:       pbCode,
 		Children:  children,
-		FieldType: ToPBFieldType(&tp),
+		FieldType: ToPBFieldType(expr.RetType),
 	}
 }
 

pkg/expression/expr_to_pb_test.go

@@ -1755,24 +1755,6 @@ func TestSortByItem2Pb(t *testing.T) {
 	require.Equal(t, "{\"expr\":{\"tp\":201,\"val\":\"gAAAAAAAAAE=\",\"sig\":0,\"field_type\":{\"tp\":5,\"flag\":0,\"flen\":-1,\"decimal\":-1,\"collate\":-63,\"charset\":\"binary\",\"array\":false},\"has_distinct\":false},\"desc\":true}", string(js))
 }
 
-func TestPushCollationDown(t *testing.T) {
-	ctx := mock.NewContext()
-	fc, err := NewFunction(ctx, ast.EQ, types.NewFieldType(mysql.TypeUnspecified), genColumn(mysql.TypeVarchar, 0), genColumn(mysql.TypeVarchar, 1))
-	require.NoError(t, err)
-	client := new(mock.Client)
-
-	tps := []*types.FieldType{types.NewFieldType(mysql.TypeVarchar), types.NewFieldType(mysql.TypeVarchar)}
-	for _, coll := range []string{charset.CollationBin, charset.CollationLatin1, charset.CollationUTF8, charset.CollationUTF8MB4} {
-		fc.SetCharsetAndCollation("binary", coll) // only collation matters
-		pbExpr, err := ExpressionsToPBList(ctx, []Expression{fc}, client)
-		require.NoError(t, err)
-		expr, err := PBToExpr(ctx, pbExpr[0], tps)
-		require.NoError(t, err)
-		_, eColl := expr.CharsetAndCollation()
-		require.Equal(t, coll, eColl)
-	}
-}
-
 func columnCollation(c *Column, chs, coll string) *Column {
 	c.RetType.SetCharset(chs)
 	c.RetType.SetCollate(coll)