FastRestore:Add comment for integrating with new backup format

fdbserver/RestoreLoader.actor.cpp

@@ -612,6 +612,11 @@ void _parseSerializedMutation(std::map<LoadingParam, VersionedMutationsMap>::ite
 }
 
 // Parsing the data blocks in a range file
+// kvOpsIter: saves the parsed versioned-mutations for the sepcific LoadingParam;
+// samplesIter: saves the sampled mutations from the parsed versioned-mutations;
+// bc: backup container to read the backup file
+// version: the version the parsed mutations should be at
+// asset: RestoreAsset about which backup data should be parsed
 ACTOR static Future<Void> _parseRangeFileToMutationsOnLoader(
     std::map<LoadingParam, VersionedMutationsMap>::iterator kvOpsIter,
     std::map<LoadingParam, MutationsVec>::iterator samplesIter, LoaderCounters* cc, Reference<IBackupContainer> bc,
@@ -691,9 +696,12 @@ ACTOR static Future<Void> _parseRangeFileToMutationsOnLoader(
 	return Void();
 }
 
-// Parse data blocks in a log file into a vector of <string, string> pairs. Each pair.second contains the mutations at a
-// version encoded in pair.first Step 1: decodeLogFileBlock into <string, string> pairs Step 2: Concatenate the
-// pair.second of pairs with the same pair.first.
+// Parse data blocks in a log file into a vector of <string, string> pairs.
+// Each pair.second contains the mutations at a version encoded in pair.first;
+// Step 1: decodeLogFileBlock into <string, string> pairs;
+// Step 2: Concatenate the second of pairs with the same pair.first.
+// pProcessedFileOffset: ensure each data block is processed in order exactly once;
+// pMutationMap: concatenated mutation list string at the mutation's commit version
 ACTOR static Future<Void> _parseLogFileToMutationsOnLoader(NotifiedVersion* pProcessedFileOffset,
                                                            SerializedMutationListMap* pMutationMap,
                                                            SerializedMutationPartMap* pMutationPartMap,

fdbserver/RestoreMaster.actor.cpp

@@ -276,6 +276,7 @@ ACTOR static Future<Version> processRestoreRequest(Reference<RestoreMasterData>
 	self->initBackupContainer(request.url);
 
 	// Get all backup files' description and save them to files
+	// TODO for Jingyu: Verify all backup files in new backup are collected
 	wait(collectBackupFiles(self->bc, &rangeFiles, &logFiles, cx, request));
 
 	std::sort(rangeFiles.begin(), rangeFiles.end());
@@ -284,6 +285,7 @@ ACTOR static Future<Version> processRestoreRequest(Reference<RestoreMasterData>
 		       std::tie(f2.endVersion, f2.beginVersion, f2.fileIndex, f2.fileName);
 	});
 
+	// TODO for Jingyu: Verify new backup files are grouped into correct version batches.
 	self->buildVersionBatches(rangeFiles, logFiles, &self->versionBatches); // Divide files into version batches
 	self->dumpVersionBatches(self->versionBatches);
 

fdbserver/RestoreRoleCommon.actor.h

@@ -51,6 +51,8 @@ struct RestoreMasterData;
 
 struct RestoreSimpleRequest;
 
+// VersionedMutationsMap: Key is the version of parsed backup mutations
+// Value MutationsVec is the vector of parsed backup mutations
 using VersionedMutationsMap = std::map<Version, MutationsVec>;
 
 ACTOR Future<Void> isSchedulable(Reference<RestoreRoleData> self, int actorBatchIndex, std::string name);