diff --git a/lib/regexutil/regexutil.go b/lib/regexutil/regexutil.go
index 6bb69dca3..e056db8f0 100644
--- a/lib/regexutil/regexutil.go
+++ b/lib/regexutil/regexutil.go
@@ -158,6 +158,9 @@ func SimplifyRegex(expr string) (string, string) {
 	prefix, suffix := simplifyRegex(expr, true)
 	sre := mustParseRegexp(suffix)
 
+	if isDotOp(sre, syntax.OpStar) {
+		return prefix, ""
+	}
 	if sre.Op == syntax.OpConcat {
 		subs := sre.Sub
 		if prefix == "" {
diff --git a/lib/regexutil/regexutil_test.go b/lib/regexutil/regexutil_test.go
index 95ad50a5b..b9eb75653 100644
--- a/lib/regexutil/regexutil_test.go
+++ b/lib/regexutil/regexutil_test.go
@@ -5,6 +5,47 @@ import (
 	"testing"
 )
 
+func TestGetOrValuesRegex(t *testing.T) {
+	f := func(s string, valuesExpected []string) {
+		t.Helper()
+		values := GetOrValuesRegex(s)
+		if !reflect.DeepEqual(values, valuesExpected) {
+			t.Fatalf("unexpected values for s=%q; got %q; want %q", s, values, valuesExpected)
+		}
+	}
+
+	f("", []string{""})
+	f("foo", []string{"foo"})
+	f("^foo$", nil)
+	f("|foo", []string{"", "foo"})
+	f("|foo|", []string{"", "", "foo"})
+	f("foo.+", nil)
+	f("foo.*", nil)
+	f(".*", nil)
+	f("foo|.*", nil)
+	f("(fo((o)))|(bar)", []string{"bar", "foo"})
+	f("foobar", []string{"foobar"})
+	f("z|x|c", []string{"c", "x", "z"})
+	f("foo|bar", []string{"bar", "foo"})
+	f("(foo|bar)", []string{"bar", "foo"})
+	f("(foo|bar)baz", []string{"barbaz", "foobaz"})
+	f("[a-z][a-z]", nil)
+	f("[a-d]", []string{"a", "b", "c", "d"})
+	f("x[a-d]we", []string{"xawe", "xbwe", "xcwe", "xdwe"})
+	f("foo(bar|baz)", []string{"foobar", "foobaz"})
+	f("foo(ba[rz]|(xx|o))", []string{"foobar", "foobaz", "fooo", "fooxx"})
+	f("foo(?:bar|baz)x(qwe|rt)", []string{"foobarxqwe", "foobarxrt", "foobazxqwe", "foobazxrt"})
+	f("foo(bar||baz)", []string{"foo", "foobar", "foobaz"})
+	f("(a|b|c)(d|e|f|0|1|2)(g|h|k|x|y|z)", nil)
+	f("(?i)foo", nil)
+	f("(?i)(foo|bar)", nil)
+	f("^foo|bar$", nil)
+	f("^(foo|bar)$", nil)
+	f("^a(foo|b(?:a|r))$", nil)
+	f("^a(foo$|b(?:a$|r))$", nil)
+	f("^a(^foo|bar$)z$", nil)
+}
+
 func TestGetOrValuesPromRegex(t *testing.T) {
 	f := func(s string, valuesExpected []string) {
 		t.Helper()
@@ -46,6 +87,83 @@ func TestGetOrValuesPromRegex(t *testing.T) {
 	f("^a(^foo|bar$)z$", nil)
 }
 
+func TestSimplifyRegex(t *testing.T) {
+	f := func(s, expectedPrefix, expectedSuffix string) {
+		t.Helper()
+		prefix, suffix := SimplifyRegex(s)
+		if prefix != expectedPrefix {
+			t.Fatalf("unexpected prefix for s=%q; got %q; want %q", s, prefix, expectedPrefix)
+		}
+		if suffix != expectedSuffix {
+			t.Fatalf("unexpected suffix for s=%q; got %q; want %q", s, suffix, expectedSuffix)
+		}
+	}
+
+	f("", "", "")
+	f(".*", "", "")
+	f(".*(.*).*", "", "")
+	f("foo.*", "foo", "")
+	f(".*foo.*", "", "foo")
+	f("^", "", "\\A")
+	f("$", "", "(?-m:$)")
+	f("^()$", "", "(?-m:\\A$)")
+	f("^(?:)$", "", "(?-m:\\A$)")
+	f("^foo|^bar$|baz", "", "(?-m:\\Afoo|\\Abar$|baz)")
+	f("^(foo$|^bar)$", "", "(?-m:\\A(?:foo$|\\Abar)$)")
+	f("^a(foo$|bar)$", "", "(?-m:\\Aa(?:foo$|bar)$)")
+	f("^a(^foo|bar$)z$", "", "(?-m:\\Aa(?:\\Afoo|bar$)z$)")
+	f("foobar", "foobar", "")
+	f("foo$|^foobar", "", "(?-m:foo$|\\Afoobar)")
+	f("^(foo$|^foobar)$", "", "(?-m:\\A(?:foo$|\\Afoobar)$)")
+	f("foobar|foobaz", "fooba", "[rz]")
+	f("(fo|(zar|bazz)|x)", "", "fo|zar|bazz|x")
+	f("(тестЧЧ|тест)", "тест", "ЧЧ|")
+	f("foo(bar|baz|bana)", "fooba", "[rz]|na")
+	f("^foobar|foobaz", "", "\\Afoobar|foobaz")
+	f("^foobar|^foobaz$", "", "(?-m:\\Afoobar|\\Afoobaz$)")
+	f("foobar|foobaz", "fooba", "[rz]")
+	f("(?:^foobar|^foobaz)aa.*", "", "(?:\\Afoobar|\\Afoobaz)aa")
+	f("foo[bar]+", "foo", "[abr]+")
+	f("foo[a-z]+", "foo", "[a-z]+")
+	f("foo[bar]*", "foo", "[abr]*")
+	f("foo[a-z]*", "foo", "[a-z]*")
+	f("foo[x]+", "foo", "x+")
+	f("foo[^x]+", "foo", "[^x]+")
+	f("foo[x]*", "foo", "x*")
+	f("foo[^x]*", "foo", "[^x]*")
+	f("foo[x]*bar", "foo", "x*bar")
+	f("fo\\Bo[x]*bar?", "fo", "\\Box*bar?")
+	f("foo.+bar", "foo", "(?s:.+bar)")
+	f("a(b|c.*).+", "a", "(?s:(?:b|c.*).+)")
+	f("ab|ac", "a", "[bc]")
+	f("(?i)xyz", "", "(?i:XYZ)")
+	f("(?i)foo|bar", "", "(?i:FOO|BAR)")
+	f("(?i)up.+x", "", "(?is:UP.+X)")
+	f("(?smi)xy.*z$", "", "(?ims:XY.*Z$)")
+
+	// test invalid regexps
+	f("a(", "a(", "")
+	f("a[", "a[", "")
+	f("a[]", "a[]", "")
+	f("a{", "a{", "")
+	f("a{}", "a{}", "")
+	f("invalid(regexp", "invalid(regexp", "")
+
+	// The transformed regexp mustn't match aba
+	f("a?(^ba|c)", "", "a?(?:\\Aba|c)")
+
+	// The transformed regexp mustn't match barx
+	f("(foo|bar$)x*", "", "(?-m:(?:foo|bar$)x*)")
+
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5297
+	f(".+;|;.+", "", "(?s:.+;|;.+)")
+	f("^(.+);|;(.+)$", "", "(?s-m:\\A.+;|;.+$)")
+	f("^(.+);$|^;(.+)$", "", "(?s-m:\\A.+;$|\\A;.+$)")
+	f(".*;|;.*", "", "(?s:.*;|;.*)")
+	f("^(.*);|;(.*)$", "", "(?s-m:\\A.*;|;.*$)")
+	f("^(.*);$|^;(.*)$", "", "(?s-m:\\A.*;$|\\A;.*$)")
+}
+
 func TestSimplifyPromRegex(t *testing.T) {
 	f := func(s, expectedPrefix, expectedSuffix string) {
 		t.Helper()