Fix bug in lbl!~".+" shortcut (#15684)

We were appending to the wrong slice, so instead of removing values, we
were adding them.

Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

tsdb/querier.go

@@ -271,7 +271,7 @@ func PostingsForMatchers(ctx context.Context, ix IndexReader, ms ...*labels.Matc
 			its = append(its, it)
 		case m.Type == labels.MatchNotRegexp && m.Value == ".+":
 			// .+ regexp matches any non-empty string: get postings for all label values and remove them.
-			its = append(notIts, ix.PostingsForAllLabelValues(ctx, m.Name))
+			notIts = append(notIts, ix.PostingsForAllLabelValues(ctx, m.Name))
 
 		case labelMustBeSet[m.Name]:
 			// If this matcher must be non-empty, we can be smarter.

tsdb/querier_test.go

@@ -3017,6 +3017,15 @@ func TestPostingsForMatchers(t *testing.T) {
 			matchers: []*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, "n", "1"), labels.MustNewMatcher(labels.MatchNotRegexp, "i", "^.*$")},
 			exp:      []labels.Labels{},
 		},
+		// Test shortcut i!~".+"
+		{
+			matchers: []*labels.Matcher{labels.MustNewMatcher(labels.MatchRegexp, "n", ".*"), labels.MustNewMatcher(labels.MatchNotRegexp, "i", ".+")},
+			exp: []labels.Labels{
+				labels.FromStrings("n", "1"),
+				labels.FromStrings("n", "2"),
+				labels.FromStrings("n", "2.5"),
+			},
+		},
 	}
 
 	ir, err := h.Index()