tsdb creation supports fingerprint overrides (#6178)

pkg/storage/stores/tsdb/builder.go

@@ -81,9 +81,14 @@ func (b *Builder) Build(
 	for _, s := range b.streams {
 		streams = append(streams, s)
 	}
+
+	// Use the supplied fingerprints instead of hashing labels for two reasons:
+	// 1) Correctness: fingerprints differ from label hashes because
+	// we add a synthesized __loki_tennat__ label, which is eventually compacted away.
+	// 2) Speed: No hashing required
 	sort.Slice(streams, func(i, j int) bool {
-		if a, b := streams[i].labels.Hash(), streams[j].labels.Hash(); a != b {
-			return a < b
+		if streams[i].fp != streams[j].fp {
+			return streams[i].fp < streams[j].fp
 		}
 		return labels.Compare(streams[i].labels, streams[j].labels) < 0
 	})

pkg/storage/stores/tsdb/index/index.go

@@ -446,7 +446,12 @@ func (w *Writer) AddSeries(ref storage.SeriesRef, lset labels.Labels, fp model.F
 		return err
 	}
 
+	// Put the supplied fingerprint instead of the calculated hash.
+	// This allows us to have a synthetic label (__loki_tenant__) in
+	// the pre-compacted TSDBs which map to fingerprints (and chunks)
+	// without this label in storage.
 	labelHash := uint64(fp)
+
 	lastHash := w.lastSeriesHash
 	// Ensure series are sorted by the priorities: [`hash(labels)`, `labels`]
 	if (labelHash < lastHash && len(w.lastSeries) > 0) || labelHash == lastHash && labels.Compare(lset, w.lastSeries) < 0 {