storage analyze

Author: y123456yz

image/单机模块化架构图.png

@@ -74,7 +74,9 @@ typedef BgInfoMap::const_iterator BgInfoMapIterator;
 
 // Static data for this file is never destroyed.
 stdx::mutex& m = *(new stdx::mutex());
+//当前真在后台加索引的库
 BgInfoMap& dbsInProg = *(new BgInfoMap());
+//当前真在后台加索引的表
 BgInfoMap& nsInProg = *(new BgInfoMap());
 
 void BgInfo::recordBegin() {

mongo/src/mongo/db/background.cpp

@@ -54,6 +54,7 @@
 #include "mongo/db/views/view.h"
 #include "mongo/util/scopeguard.h"
 
+//EmptyCapped::run->mongo::emptyCapped
 mongo::Status mongo::emptyCapped(OperationContext* opCtx, const NamespaceString& collectionName) {
     AutoGetDb autoDb(opCtx, collectionName.db(), MODE_X);
 

mongo/src/mongo/db/catalog/capped_utils.cpp

@@ -178,12 +178,13 @@ CollectionImpl::CollectionImpl(Collection* _this_init,
 
 void CollectionImpl::init(OperationContext* opCtx) {
     _magic = kMagicNumber;
-	//IndexCatalogImpl::init
+	//IndexCatalogImpl::init 获取该表下面的所有索引信息
     _indexCatalog.init(opCtx).transitional_ignore();
     if (isCapped())
         _recordStore->setCappedCallback(this);
 
 	//CollectionInfoCacheImpl::init
+	//初始化该集合的planCache IndexEntry
     _infoCache.init(opCtx);
 }
 
@@ -207,6 +208,7 @@ CollectionImpl::~CollectionImpl() {
     _magic = 0;
 }
 
+//除了system.indexes  system.namespaces   system.profile外的其他表都需要id索引
 bool CollectionImpl::requiresIdIndex() const {
     if (_ns.isVirtualized() || _ns.isOplog()) {
         // No indexes on virtual collections or the oplog.
@@ -223,6 +225,7 @@ bool CollectionImpl::requiresIdIndex() const {
     return true;
 }
 
+//获取SeekableRecordCursor游标
 std::unique_ptr<SeekableRecordCursor> CollectionImpl::getCursor(OperationContext* opCtx,
                                                                 bool forward) const {
     dassert(opCtx->lockState()->isCollectionLockedForMode(ns().toString(), MODE_IS));
@@ -726,6 +729,7 @@ RecordId CollectionImpl::updateDocument(OperationContext* opCtx,
     Status updateStatus = _recordStore->updateRecord(
         opCtx, oldLocation, newDoc.objdata(), newDoc.objsize(), _enforceQuota(enforceQuota), this);
 
+	//mmap才会有该错误状态码
     if (updateStatus == ErrorCodes::NeedsDocumentMove) {
         return uassertStatusOK(_updateDocumentWithMove(
             opCtx, oldLocation, oldDoc, newDoc, enforceQuota, opDebug, args, sid));
@@ -758,6 +762,7 @@ RecordId CollectionImpl::updateDocument(OperationContext* opCtx,
     return {oldLocation};
 }
 
+//mmap才会用到
 StatusWith<RecordId> CollectionImpl::_updateDocumentWithMove(OperationContext* opCtx,
                                                              const RecordId& oldLocation,
                                                              const Snapshotted<BSONObj>& oldDoc,
@@ -853,6 +858,7 @@ StatusWith<RecordData> CollectionImpl::updateDocumentWithDamages(
     return newRecStatus;
 }
 
+//针对mmapv1引擎，忽略
 bool CollectionImpl::_enforceQuota(bool userEnforeQuota) const {
     if (!userEnforeQuota)
         return false;
@@ -869,6 +875,7 @@ bool CollectionImpl::_enforceQuota(bool userEnforeQuota) const {
     return true;
 }
 
+//是否固定集合
 bool CollectionImpl::isCapped() const {
     return _cappedNotifier.get();
 }
@@ -918,7 +925,9 @@ uint64_t CollectionImpl::getIndexSize(OperationContext* opCtx, BSONObjBuilder* d
  * 2) drop indexes
  * 3) truncate record store
  * 4) re-write indexes
- */ //drop表数据，但是不drop索引
+ */ 
+//EmptyCapped::run->mongo::emptyCapped调用
+//drop表数据，但是不drop索引
 Status CollectionImpl::truncate(OperationContext* opCtx) {
     dassert(opCtx->lockState()->isCollectionLockedForMode(ns().toString(), MODE_X));
     BackgroundOperation::assertNoBgOpInProgForNs(ns());
@@ -953,6 +962,7 @@ Status CollectionImpl::truncate(OperationContext* opCtx) {
     return Status::OK();
 }
 
+//captrunc::run命令调用，测试使用
 void CollectionImpl::cappedTruncateAfter(OperationContext* opCtx, RecordId end, bool inclusive) {
     dassert(opCtx->lockState()->isCollectionLockedForMode(ns().toString(), MODE_X));
     invariant(isCapped());
@@ -1135,6 +1145,7 @@ namespace {
 
 using ValidateResultsMap = std::map<std::string, ValidateResults>;
 
+//CollectionImpl::validate调用
 void _validateRecordStore(OperationContext* opCtx,
                           RecordStore* recordStore,
                           ValidateCmdLevel level,
@@ -1155,6 +1166,7 @@ void _validateRecordStore(OperationContext* opCtx,
     }
 }
 
+//CollectionImpl::validate调用
 void _validateIndexes(OperationContext* opCtx,
                       IndexCatalog* indexCatalog,
                       BSONObjBuilder* keysPerIndex,
@@ -1206,6 +1218,7 @@ void _validateIndexes(OperationContext* opCtx,
     }
 }
 
+//CollectionImpl::validate调用
 void _markIndexEntriesInvalid(ValidateResultsMap* indexNsResultsMap, ValidateResults* results) {
 
     // The error message can't be more specific because even though the index is
@@ -1221,6 +1234,7 @@ void _markIndexEntriesInvalid(ValidateResultsMap* indexNsResultsMap, ValidateRes
     results->valid = false;
 }
 
+//CollectionImpl::validate调用
 void _validateIndexKeyCount(OperationContext* opCtx,
                             IndexCatalog* indexCatalog,
                             RecordStore* recordStore,
@@ -1239,6 +1253,7 @@ void _validateIndexKeyCount(OperationContext* opCtx,
     }
 }
 
+//CollectionImpl::validate调用
 void _reportValidationResults(OperationContext* opCtx,
                               IndexCatalog* indexCatalog,
                               ValidateResultsMap* indexNsResultsMap,
@@ -1286,6 +1301,9 @@ void _reportValidationResults(OperationContext* opCtx,
 }
 }  // namespace
 
+//db.xx.validate()
+//https://docs.mongodb.com/v3.0/reference/command/validate/index.html
+//该命令验证表中数据结构是否符合要求，因为建表的时候可能指定了validator
 Status CollectionImpl::validate(OperationContext* opCtx,
                                 ValidateCmdLevel level,
                                 bool background,
@@ -1351,6 +1369,10 @@ Status CollectionImpl::validate(OperationContext* opCtx,
     return Status::OK();
 }
 
+//touch::run touch命令调用
+//db.runCommand({ touch: "records", data: true, index: true })
+//加载表的数据和索引到内存
+//参考https://docs.mongodb.com/v3.0/reference/command/touch/index.html
 Status CollectionImpl::touch(OperationContext* opCtx,
                              bool touchData,
                              bool touchIndexes,

mongo/src/mongo/db/catalog/collection_impl.cpp

@@ -218,6 +218,7 @@ void CollectionInfoCacheImpl::updatePlanCacheIndexEntries(OperationContext* opCt
 		//获取索引信息
         const IndexDescriptor* desc = ii.next();
         const IndexCatalogEntry* ice = ii.catalogEntry(desc);
+		//完成IndexEntry和IndexDescriptor的转换
         indexEntries.emplace_back(desc->keyPattern(),
                                   desc->getAccessMethodName(),
                                   desc->isMultikey(opCtx),
@@ -235,23 +236,27 @@ void CollectionInfoCacheImpl::updatePlanCacheIndexEntries(OperationContext* opCt
 }
 
 //CollectionImpl::init中调用
+//初始化该集合的planCache IndexEntry
 void CollectionInfoCacheImpl::init(OperationContext* opCtx) {
     // Requires exclusive collection lock.
     invariant(opCtx->lockState()->isCollectionLockedForMode(_collection->ns().ns(), MODE_X));
 
     const bool includeUnfinishedIndexes = false;
     IndexCatalog::IndexIterator ii =
         _collection->getIndexCatalog()->getIndexIterator(opCtx, includeUnfinishedIndexes);
-    while (ii.more()) {
+	//遍历该表的所有索引信息注册到_indexUsageTracker
+	while (ii.more()) {
         const IndexDescriptor* desc = ii.next();
         _indexUsageTracker.registerIndex(desc->indexName(), desc->keyPattern());
     }
 
+	//重新生产索引data 重新生成planCache的IndexEntry
     rebuildIndexData(opCtx);
 }
 
 //通过类似_collection->infoCache()->addedIndex(_opCtx, descriptorPtr);方式调用，参考IndexCatalogImpl::IndexBuildBlock::init()
 //IndexCatalogImpl::IndexBuildBlock::init()调用
+//新索引注册到_indexUsageTracker
 void CollectionInfoCacheImpl::addedIndex(OperationContext* opCtx, const IndexDescriptor* desc) {
     // Requires exclusive collection lock.
     invariant(opCtx->lockState()->isCollectionLockedForMode(_collection->ns().ns(), MODE_X));
@@ -263,6 +268,7 @@ void CollectionInfoCacheImpl::addedIndex(OperationContext* opCtx, const IndexDes
 }
 
 //IndexCatalogImpl::_dropIndex调用
+//从_indexUsageTracker中注销索引
 void CollectionInfoCacheImpl::droppedIndex(OperationContext* opCtx, StringData indexName) {
     // Requires exclusive collection lock.
     invariant(opCtx->lockState()->isCollectionLockedForMode(_collection->ns().ns(), MODE_X));
@@ -273,6 +279,7 @@ void CollectionInfoCacheImpl::droppedIndex(OperationContext* opCtx, StringData i
 
 //CollectionInfoCacheImpl::init   CollectionInfoCacheImpl::addedIndex   
 //CollectionInfoCacheImpl::droppedIndex调用
+//重新生成planCache的IndexEntry
 void CollectionInfoCacheImpl::rebuildIndexData(OperationContext* opCtx) {
 	//清除缓存的querycache
     clearQueryCache();

mongo/src/mongo/db/catalog/collection_info_cache_impl.cpp

@@ -111,6 +111,8 @@ struct CollectionOptions {
     // Collection UUID. Will exist if featureCompatibilityVersion >= 3.6.
     OptionalCollectionUUID uuid; //每个collection会对应一个uuid，见DatabaseImpl::createCollection，只有3.6以上版本有该uuid
     //说明是MongoDB固定集合（capped collection）
+    //可以通过下面的方式创建固定集合
+    //db.createCollection("xx",{capped:true, size: 1000000})
     bool capped = false;
     long long cappedSize = 0;
     long long cappedMaxDocs = 0;