TSDB: don't process exemplars older than minValidTime during WAL replay

Signed-off-by: Patryk Prus <p@trykpr.us>

tsdb/head_wal.go

@@ -142,10 +142,6 @@ func (h *Head) loadWAL(r *wlog.Reader, syms *labels.SymbolTable, multiRef map[ch
 				missingSeries[e.Ref] = struct{}{}
 				continue
 			}
-
-			if e.T < h.minValidTime.Load() {
-				continue
-			}
 			// At the moment the only possible error here is out of order exemplars, which we shouldn't see when
 			// replaying the WAL, so lets just log the error if it's not that type.
 			err = h.exemplars.AddExemplar(ms.labels(), exemplar.Exemplar{Ts: e.T, Value: e.V, Labels: e.Labels})
@@ -334,6 +330,9 @@ Outer:
 			h.wlReplaytStonesPool.Put(v)
 		case []record.RefExemplar:
 			for _, e := range v {
+				if e.T < h.minValidTime.Load() {
+					continue
+				}
 				if r, ok := multiRef[e.Ref]; ok {
 					e.Ref = r
 				}