fix(storage/mergeQuerier): copy the matcjers slice before passing it to queriers as

some of them may alter it.

Signed-off-by: machine424 <ayoubmrini424@gmail.com>

storage/merge.go

@@ -155,19 +155,16 @@ func (q *mergeGenericQuerier) Select(ctx context.Context, sortSeries bool, hints
 	for _, querier := range q.queriers {
 		// copy the matchers as some queriers may alter the slice.
 		// See https://github.com/prometheus/prometheus/issues/14723
-		// matchersCopy := make([]*labels.Matcher, len(matchers))
-		// copy(matchersCopy, matchers)
+		matchersCopy := make([]*labels.Matcher, len(matchers))
+		copy(matchersCopy, matchers)
 
 		wg.Add(1)
-		go func(qr genericQuerier) {
-			// go func(qr genericQuerier, m []*labels.Matcher) {
+		go func(qr genericQuerier, m []*labels.Matcher) {
 			defer wg.Done()
 
 			// We need to sort for NewMergeSeriesSet to work.
-			// seriesSetChan <- qr.Select(ctx, true, hints, m...)
-			seriesSetChan <- qr.Select(ctx, true, hints, matchers...)
-		}(querier)
-		// }(querier, matchersCopy)
+			seriesSetChan <- qr.Select(ctx, true, hints, m...)
+		}(querier, matchersCopy)
 	}
 	go func() {
 		wg.Wait()

tsdb/querier_test.go

@@ -3794,6 +3794,9 @@ func (m mockReaderOfLabels) Symbols() index.StringIter {
 func TestMergeQuerierConcurrentSelectMatchers(t *testing.T) {
 	block, err := OpenBlock(nil, createBlock(t, t.TempDir(), genSeries(1, 1, 0, 1)), nil)
 	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, block.Close())
+	}()
 	p, err := NewBlockQuerier(block, 0, 1)
 	require.NoError(t, err)
 
@@ -3808,7 +3811,10 @@ func TestMergeQuerierConcurrentSelectMatchers(t *testing.T) {
 	matchers := append([]*labels.Matcher{}, originalMatchers...)
 
 	mergedQuerier := storage.NewMergeQuerier([]storage.Querier{p}, []storage.Querier{s}, storage.ChainedSeriesMerge)
-	defer mergedQuerier.Close()
+	defer func() {
+		require.NoError(t, mergedQuerier.Close())
+	}()
+
 	mergedQuerier.Select(context.Background(), false, nil, matchers...)
 
 	require.Equal(t, originalMatchers, matchers)