lib/storage: fix matching against tag filter with empty name

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/137

lib/storage/index_db.go

@@ -1430,7 +1430,7 @@ func matchTagFilters(mn *MetricName, tfs []*tagFilter, kb *bytesutil.ByteBuffer)
 				continue
 			}
 
-			// Found the matching tag name. Match for the value.
+			// Found the matching tag name. Match the value.
 			b := tag.Marshal(kb.B)
 			kb.B = b[:len(kb.B)]
 			ok, err := matchTagFilter(b, tf)
@@ -1443,7 +1443,7 @@ func matchTagFilters(mn *MetricName, tfs []*tagFilter, kb *bytesutil.ByteBuffer)
 			tagMatched = true
 			break
 		}
-		if !tagMatched {
+		if !tagMatched && !tf.isNegative {
 			// Matching tag name wasn't found.
 			return false, nil
 		}

lib/storage/index_db_test.go

@@ -804,8 +804,8 @@ func TestMatchTagFilters(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected error: %s", err)
 	}
-	if ok {
+	if !ok {
-		t.Fatalf("Shouldn't match")
+		t.Fatalf("Should match")
 	}
 	tfs.Reset(mn.AccountID, mn.ProjectID)
 	if err := tfs.Add([]byte("non-existing-tag"), []byte("foob.+metric"), true, true); err != nil {
@@ -815,8 +815,19 @@ func TestMatchTagFilters(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected error: %s", err)
 	}
-	if ok {
+	if !ok {
-		t.Fatalf("Shouldn't match")
+		t.Fatalf("Should match")
+	}
+	tfs.Reset(mn.AccountID, mn.ProjectID)
+	if err := tfs.Add([]byte("non-existing-tag"), []byte(".+"), true, true); err != nil {
+		t.Fatalf("cannot add regexp, negative filter: %s", err)
+	}
+	ok, err = matchTagFilters(&mn, toTFPointers(tfs.tfs), &bb)
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+	if !ok {
+		t.Fatalf("Should match")
 	}
 
 	// Negative match by existing tag
@@ -910,6 +921,17 @@ func TestMatchTagFilters(t *testing.T) {
 	if !ok {
 		t.Fatalf("Should match")
 	}
+	tfs.Reset(mn.AccountID, mn.ProjectID)
+	if err := tfs.Add([]byte("key 3"), []byte(""), true, false); err != nil {
+		t.Fatalf("cannot add regexp, negative filter: %s", err)
+	}
+	ok, err = matchTagFilters(&mn, toTFPointers(tfs.tfs), &bb)
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+	if !ok {
+		t.Fatalf("Should match")
+	}
 
 	// Positive match by multiple tags and MetricGroup
 	tfs.Reset(mn.AccountID, mn.ProjectID)

lib/storage/tag_filters_test.go

@@ -308,6 +308,62 @@ func TestTagFilterMatchSuffix(t *testing.T) {
 		mismatch("bar")
 		match("xhttpbar")
 	})
+	t.Run("non-empty-string-regexp-negative-match", func(t *testing.T) {
+		value := ".+"
+		isNegative := true
+		isRegexp := true
+		expectedPrefix := tvNoTrailingTagSeparator("")
+		init(value, isNegative, isRegexp, expectedPrefix)
+		if len(tf.orSuffixes) != 0 {
+			t.Fatalf("unexpected non-zero number of or suffixes: %d; %q", len(tf.orSuffixes), tf.orSuffixes)
+		}
+
+		match("")
+		mismatch("x")
+		mismatch("foo")
+	})
+	t.Run("non-empty-string-regexp-match", func(t *testing.T) {
+		value := ".+"
+		isNegative := false
+		isRegexp := true
+		expectedPrefix := tvNoTrailingTagSeparator("")
+		init(value, isNegative, isRegexp, expectedPrefix)
+		if len(tf.orSuffixes) != 0 {
+			t.Fatalf("unexpected non-zero number of or suffixes: %d; %q", len(tf.orSuffixes), tf.orSuffixes)
+		}
+
+		mismatch("")
+		match("x")
+		match("foo")
+	})
+	t.Run("match-all-regexp-negative-match", func(t *testing.T) {
+		value := ".*"
+		isNegative := true
+		isRegexp := true
+		expectedPrefix := tvNoTrailingTagSeparator("")
+		init(value, isNegative, isRegexp, expectedPrefix)
+		if len(tf.orSuffixes) != 0 {
+			t.Fatalf("unexpected non-zero number of or suffixes: %d; %q", len(tf.orSuffixes), tf.orSuffixes)
+		}
+
+		mismatch("")
+		mismatch("x")
+		mismatch("foo")
+	})
+	t.Run("match-all-regexp-match", func(t *testing.T) {
+		value := ".*"
+		isNegative := false
+		isRegexp := true
+		expectedPrefix := tvNoTrailingTagSeparator("")
+		init(value, isNegative, isRegexp, expectedPrefix)
+		if len(tf.orSuffixes) != 0 {
+			t.Fatalf("unexpected non-zero number of or suffixes: %d; %q", len(tf.orSuffixes), tf.orSuffixes)
+		}
+
+		match("")
+		match("x")
+		match("foo")
+	})
 }
 
 func TestGetOrValues(t *testing.T) {