Convert LIKE patterns to specific Go regexes (#817)

Convert LIKE patterns to specific Go regexes

Author: ajnavarro

sql/expression/like.go

@@ -68,11 +68,11 @@ func (l *Like) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
 		if err != nil {
 			return nil, err
 		}
-		right = patternToRegex(v.(string))
+		right = patternToGoRegex(v.(string))
 	}
 	// for non-cached regex every time create a new matcher
 	if !l.cached {
-		matcher, disposer, err = regex.New(regex.Default(), right)
+		matcher, disposer, err = regex.New("go", right)
 	} else {
 		if l.pool == nil {
 			l.pool = &sync.Pool{
@@ -115,8 +115,9 @@ func (l *Like) WithChildren(children ...sql.Expression) (sql.Expression, error)
 	return NewLike(children[0], children[1]), nil
 }
 
-func patternToRegex(pattern string) string {
+func patternToGoRegex(pattern string) string {
 	var buf bytes.Buffer
+	buf.WriteString("(?s)")
 	buf.WriteRune('^')
 	var escaped bool
 	for _, r := range strings.Replace(regexp.QuoteMeta(pattern), `\\`, `\`, -1) {

sql/expression/like_test.go

@@ -12,23 +12,23 @@ func TestPatternToRegex(t *testing.T) {
 	testCases := []struct {
 		in, out string
 	}{
-		{`__`, `^..$`},
-		{`_%_`, `^..*.$`},
-		{`%_`, `^.*.$`},
-		{`_%`, `^..*$`},
-		{`a_b`, `^a.b$`},
-		{`a%b`, `^a.*b$`},
-		{`a.%b`, `^a\..*b$`},
-		{`a\%b`, `^a%b$`},
-		{`a\_b`, `^a_b$`},
-		{`a\\b`, `^a\\b$`},
-		{`a\\\_b`, `^a\\_b$`},
-		{`(ab)`, `^\(ab\)$`},
+		{`__`, `(?s)^..$`},
+		{`_%_`, `(?s)^..*.$`},
+		{`%_`, `(?s)^.*.$`},
+		{`_%`, `(?s)^..*$`},
+		{`a_b`, `(?s)^a.b$`},
+		{`a%b`, `(?s)^a.*b$`},
+		{`a.%b`, `(?s)^a\..*b$`},
+		{`a\%b`, `(?s)^a%b$`},
+		{`a\_b`, `(?s)^a_b$`},
+		{`a\\b`, `(?s)^a\\b$`},
+		{`a\\\_b`, `(?s)^a\\_b$`},
+		{`(ab)`, `(?s)^\(ab\)$`},
 	}
 
 	for _, tt := range testCases {
 		t.Run(tt.in, func(t *testing.T) {
-			require.Equal(t, tt.out, patternToRegex(tt.in))
+			require.Equal(t, tt.out, patternToGoRegex(tt.in))
 		})
 	}
 }