Revert "[dbnode] Remove allocation per series ID when streaming block…

… from disk (#3093)"

This reverts commit 5b4f793.

src/dbnode/network/server/tchannelthrift/node/service.go

@@ -808,14 +808,12 @@ func (s *service) fetchReadEncoded(ctx context.Context,
 	// Re-use reader and id for more memory-efficient processing of
 	// tags from doc.Metadata
 	reader := docs.NewEncodedDocumentReader()
+	id := ident.NewReusableBytesID()
 	for _, entry := range results.Map().Iter() {
 		idx := i
 		i++
 
-		// NB(r): Use a bytes ID here so that this ID doesn't need to be
-		// copied by the blockRetriever in the streamRequest method when
-		// it checks if the ID is finalizeable or not with IsNoFinalize.
-		id := ident.BytesID(entry.Key())
+		id.Reset(entry.Key())
 
 		d := entry.Value()
 		metadata, err := docs.MetadataFromDocument(d, reader)

src/dbnode/persist/fs/retriever.go

@@ -575,17 +575,9 @@ func (r *blockRetriever) streamRequest(
 		return false, err
 	}
 	req.shard = shard
-
-	// NB(r): If the ID is a ident.BytesID then we can just hold
-	// onto this ID.
-	seriesID := id
-	if !seriesID.IsNoFinalize() {
-		// NB(r): Clone the ID as we're not positive it will stay valid throughout
-		// the lifecycle of the async request.
-		seriesID = r.idPool.Clone(id)
-	}
-
-	req.id = seriesID
+	// NB(r): Clone the ID as we're not positive it will stay valid throughout
+	// the lifecycle of the async request.
+	req.id = r.idPool.Clone(id)
 	req.start = startTime
 	req.blockSize = r.blockSize