feat: dont compile regex matcher if we know its a literal (#12434)

labels: dont compile regex matcher if we know its a literal

Signed-off-by: Michael Hoffmann <mhoffm@posteo.de>

Co-authored-by: Sharad <sharadgaur@gmail.com>

model/labels/matcher_test.go

@@ -102,12 +102,12 @@ func TestInverse(t *testing.T) {
 			expected: &Matcher{Type: MatchEqual, Name: "name2", Value: "value2"},
 		},
 		{
-			matcher:  &Matcher{Type: MatchRegexp, Name: "name3", Value: "value3"},
-			expected: &Matcher{Type: MatchNotRegexp, Name: "name3", Value: "value3"},
+			matcher:  &Matcher{Type: MatchRegexp, Name: "name3", Value: "value3.*"},
+			expected: &Matcher{Type: MatchNotRegexp, Name: "name3", Value: "value3.*"},
 		},
 		{
-			matcher:  &Matcher{Type: MatchNotRegexp, Name: "name4", Value: "value4"},
-			expected: &Matcher{Type: MatchRegexp, Name: "name4", Value: "value4"},
+			matcher:  &Matcher{Type: MatchNotRegexp, Name: "name4", Value: "value4.*"},
+			expected: &Matcher{Type: MatchRegexp, Name: "name4", Value: "value4.*"},
 		},
 	}
 
@@ -123,3 +123,13 @@ func BenchmarkMatchType_String(b *testing.B) {
 		_ = MatchType(i % int(MatchNotRegexp+1)).String()
 	}
 }
+
+func BenchmarkNewMatcher(b *testing.B) {
+	b.Run("regex matcher with literal", func(b *testing.B) {
+		b.ReportAllocs()
+		b.ResetTimer()
+		for i := 0; i <= b.N; i++ {
+			NewMatcher(MatchRegexp, "foo", "bar")
+		}
+	})
+}

model/labels/regexp.go

@@ -25,9 +25,16 @@ type FastRegexMatcher struct {
 	prefix   string
 	suffix   string
 	contains string
+
+	// shortcut for literals
+	literal bool
+	value   string
 }
 
 func NewFastRegexMatcher(v string) (*FastRegexMatcher, error) {
+	if isLiteral(v) {
+		return &FastRegexMatcher{literal: true, value: v}, nil
+	}
 	re, err := regexp.Compile("^(?:" + v + ")$")
 	if err != nil {
 		return nil, err
@@ -50,6 +57,9 @@ func NewFastRegexMatcher(v string) (*FastRegexMatcher, error) {
 }
 
 func (m *FastRegexMatcher) MatchString(s string) bool {
+	if m.literal {
+		return s == m.value
+	}
 	if m.prefix != "" && !strings.HasPrefix(s, m.prefix) {
 		return false
 	}
@@ -63,9 +73,16 @@ func (m *FastRegexMatcher) MatchString(s string) bool {
 }
 
 func (m *FastRegexMatcher) GetRegexString() string {
+	if m.literal {
+		return m.value
+	}
 	return m.re.String()
 }
 
+func isLiteral(re string) bool {
+	return regexp.QuoteMeta(re) == re
+}
+
 // optimizeConcatRegex returns literal prefix/suffix text that can be safely
 // checked against the label value before running the regexp matcher.
 func optimizeConcatRegex(r *syntax.Regexp) (prefix, suffix, contains string) {