MongoDB-09-存储引擎模块-数据结构

1. 核心数据结构概览

存储引擎模块的数据结构设计实现了MongoDB的持久化存储功能，支持多种存储引擎（主要是WiredTiger）的统一抽象。数据结构按功能分为几个主要层次：

1.1 数据结构分类

存储引擎抽象层： StorageEngine、KVEngine
记录存储层： RecordStore、SeekableRecordCursor
事务管理层： RecoveryUnit、Change
索引存储层： SortedDataInterface、SortedDataBuilderInterface
目录管理层： KVCatalog、WiredTigerCatalog
缓存管理层： KVDrop pendings、SizeStorer

2. 核心类图

2.1 存储引擎抽象层类图

classDiagram
    class StorageEngine {
        <<abstract>>
        +loadCatalog(opCtx, stableTimestamp) void
        +listDatabases(out) void
        +createRecordStore(opCtx, nss, options) Status
        +getRecordStore(opCtx, nss, ident, options) unique_ptr~RecordStore~
        +createSortedDataInterface(opCtx, collOptions, ident, desc) Status
        +getSortedDataInterface(opCtx, collOptions, ident, desc) unique_ptr~SortedDataInterface~
        +newRecoveryUnit() unique_ptr~RecoveryUnit~
        +createCheckpoint(opCtx) Status
        +getStableTimestamp() Timestamp
        +setStableTimestamp(timestamp, force) void
        +beginBackup(opCtx) StatusWith~vector~string~~
        +endBackup(opCtx) void
        +isDurable() bool
        +isEphemeral() bool
        +supportsCappedCollections() bool
        +supportsDocLocking() bool
    }

    class KVEngine {
        <<abstract>>
        +getAllIdents(opCtx) vector~string~
        +recoverToStableTimestamp(opCtx) Status
        +cleanShutdown() void
        +flushAllFiles(opCtx, callerHoldsReadLock) Status
        +beginNonBlockingBackup(opCtx, options) StatusWith~StorageEngine::BackupInformation~
        +endNonBlockingBackup(opCtx) void
        +disableIncrementalBackup(opCtx) Status
        +getMetadata(opCtx, ident) BSONObj
        +setMetadata(opCtx, ident, metadata) Status
    }

    class WiredTigerKVEngine {
        -WT_CONNECTION* _conn
        -unique_ptr~WiredTigerSessionCache~ _sessionCache
        -unique_ptr~WiredTigerCatalog~ _catalog
        -string _canonicalName
        -string _path
        -bool _durable
        -bool _ephemeral
        -WiredTigerEventHandler _eventHandler
        -unique_ptr~WiredTigerSizeStorer~ _sizeStorer
        -mutable Mutex _dropPendingQueueMutex
        -WiredTigerDropPendingQueue _dropPendingQueue
        +WiredTigerKVEngine(canonicalName, path, cs, extraOpenOptions, cacheMB, maxHistoryFileSizeMB, ephemeral, repair)
        +loadCatalog(opCtx, stableTimestamp) void
        +createRecordStore(opCtx, nss, options) Status
        +getRecordStore(opCtx, nss, ident, options) unique_ptr~RecordStore~
        +createCheckpoint(opCtx) Status
        +flushAllFiles(opCtx, callerHoldsReadLock) Status
        +getConnection() WT_CONNECTION*
        +getSession(opCtx) WT_SESSION*
        +releaseSession(session) void
        -_initConnection(options) Status
        -_createIdent(nss, options) string
        -_postCreateCollection(opCtx, ident, metadata) void
    }

    class DevNullKVEngine {
        -map~string, shared_ptr~DevNullRecordStore~~ _recordStores
        -map~string, shared_ptr~DevNullSortedDataInterface~~ _sortedDataInterfaces
        -mutable Mutex _mutex
        +loadCatalog(opCtx, stableTimestamp) void
        +createRecordStore(opCtx, nss, options) Status
        +getRecordStore(opCtx, nss, ident, options) unique_ptr~RecordStore~
        +newRecoveryUnit() unique_ptr~RecoveryUnit~
        +isDurable() bool
        +isEphemeral() bool
    }

    StorageEngine <|-- KVEngine
    KVEngine <|-- WiredTigerKVEngine
    KVEngine <|-- DevNullKVEngine
    WiredTigerKVEngine --> WiredTigerCatalog : manages
    WiredTigerKVEngine --> WiredTigerSessionCache : uses

2.2 记录存储层类图

classDiagram
    class RecordStore {
        <<abstract>>
        +insertRecord(opCtx, data, len, out) Status
        +insertRecords(opCtx, records, timestamps) Status
        +updateRecord(opCtx, recordId, data, len) Status
        +deleteRecord(opCtx, recordId) Status
        +dataFor(opCtx, recordId) RecordData
        +findRecord(opCtx, recordId, out) bool
        +getCursor(opCtx, forward) unique_ptr~SeekableRecordCursor~
        +numRecords(opCtx) int64_t
        +dataSize(opCtx) int64_t
        +storageSize(opCtx) int64_t
        +isCapped() bool
        +isOplog() bool
        +setCappedCallback(cb) void
        +validate(opCtx, results, output) Status
        +doDeleteRecord(opCtx, recordId) void
    }

    class WiredTigerRecordStore {
        -WiredTigerKVEngine* _kvEngine
        -string _nss
        -string _ident
        -string _tableURI
        -bool _isOplog
        -bool _isCapped
        -shared_ptr~CappedCallback~ _cappedCallback
        -mutable AtomicWord~long long~ _numRecords
        -mutable AtomicWord~long long~ _dataSize
        -unique_ptr~WiredTigerSizeStorer~ _sizeStorer
        -string _sizeStorerUri
        -AtomicWord~long long~ _nextRecordId
        +WiredTigerRecordStore(kvEngine, opCtx, nss, ident, isOplog, cappedCallback)
        +insertRecord(opCtx, data, len, out) Status
        +updateRecord(opCtx, recordId, data, len) Status
        +deleteRecord(opCtx, recordId) Status
        +dataFor(opCtx, recordId) RecordData
        +getCursor(opCtx, forward) unique_ptr~SeekableRecordCursor~
        +validate(opCtx, results, output) Status
        -_generateOplogRecordId(opCtx) RecordId
        -_nextRecordId() RecordId
        -_increaseDataSize(amount) void
        -_decreaseDataSize(amount) void
    }

    class DevNullRecordStore {
        -string _ns
        -mutable Mutex _recordsMutex
        -map~RecordId, string~ _records
        -AtomicWord~long long~ _nextRecordId
        +insertRecord(opCtx, data, len, out) Status
        +deleteRecord(opCtx, recordId) Status
        +dataFor(opCtx, recordId) RecordData
        +getCursor(opCtx, forward) unique_ptr~SeekableRecordCursor~
        +numRecords(opCtx) int64_t
        +isCapped() bool
        +isOplog() bool
    }

    class SeekableRecordCursor {
        <<abstract>>
        +next() boost::optional~Record~
        +seekExact(id) boost::optional~Record~
        +seekNear(id) boost::optional~Record~
        +save() void
        +restore() bool
        +detachFromOperationContext() void
        +reattachToOperationContext(opCtx) void
    }

    class WiredTigerRecordStoreCursor {
        -WiredTigerRecoveryUnit* _ru
        -string _uri
        -WT_CURSOR* _cursor
        -bool _forward
        -bool _positioned
        -RecordId _lastReturnedId
        +WiredTigerRecordStoreCursor(opCtx, rs, forward)
        +next() boost::optional~Record~
        +seekExact(id) boost::optional~Record~
        +save() void
        +restore() bool
        -_getNext() boost::optional~Record~
        -_skipToNext() void
    }

    class RecordData {
        -SharedBuffer _buffer
        -int _size
        +RecordData()
        +RecordData(data, size)
        +data() const char*
        +size() int
        +isNull() bool
        +getOwned() RecordData
        +toBson() BSONObj
    }

    class RecordId {
        -int64_t _id
        -string _str
        -Type _type
        +RecordId()
        +RecordId(id)
        +RecordId(str)
        +repr() int64_t
        +isLong() bool
        +isStr() bool
        +toString() string
        +compare(other) int
        +operator<(other) bool
        +operator==(other) bool
        +isValid() bool
    }

    RecordStore <|-- WiredTigerRecordStore
    RecordStore <|-- DevNullRecordStore
    RecordStore --> SeekableRecordCursor : creates
    SeekableRecordCursor <|-- WiredTigerRecordStoreCursor
    RecordStore --> RecordData : returns
    RecordStore --> RecordId : uses
    WiredTigerRecordStore --> WiredTigerKVEngine : uses

2.3 事务管理层类图

classDiagram
    class RecoveryUnit {
        <<abstract>>
        +beginUnitOfWork(opCtx) void
        +commitUnitOfWork() void
        +abortUnitOfWork() void
        +waitUntilDurable(opCtx) bool
        +waitUntilUnjournaledWritesDurable(opCtx) bool
        +abandonSnapshot() void
        +setTimestamp(timestamp) Status
        +getTimestamp() Timestamp
        +registerChange(change) void
        +onRollback(callback) void
        +onCommit(callback) void
        +inUnitOfWork() bool
        +hasUncommittedWrites() bool
        +setReadOnce(readOnce) void
        +getReadOnce() bool
    }

    class WiredTigerRecoveryUnit {
        -WT_SESSION* _session
        -WiredTigerKVEngine* _kvEngine
        -WiredTigerSessionCache* _sessionCache
        -bool _inUnitOfWork
        -bool _hasUncommittedWrites
        -bool _isTimestamped
        -Timestamp _commitTimestamp
        -Timestamp _durableTimestamp
        -Timestamp _readAtTimestamp
        -bool _roundUpToIncludeEndOfBatch
        -vector~unique_ptr~Change~~ _changes
        -vector~function~void()~~ _onCommitCallbacks
        -vector~function~void()~~ _onRollbackCallbacks
        -map~string, WT_CURSOR*~ _cursors
        -int _myTransactionCount
        +WiredTigerRecoveryUnit(sessionCache, kvEngine)
        +beginUnitOfWork(opCtx) void
        +commitUnitOfWork() void
        +abortUnitOfWork() void
        +setTimestamp(timestamp) Status
        +getSession() WT_SESSION*
        +getCursor(uri, forRecordStore) WT_CURSOR*
        +waitUntilDurable(opCtx) bool
        -_isTimestamped() bool
        -_prepareForSnapshot(opCtx) void
        -_txnClose(commit) void
        -_getTransactionConfigString() string
    }

    class DevNullRecoveryUnit {
        -bool _inUnitOfWork
        -vector~unique_ptr~Change~~ _changes
        -vector~function~void()~~ _onCommitCallbacks
        -vector~function~void()~~ _onRollbackCallbacks
        +beginUnitOfWork(opCtx) void
        +commitUnitOfWork() void
        +abortUnitOfWork() void
        +waitUntilDurable(opCtx) bool
        +inUnitOfWork() bool
    }

    class Change {
        <<abstract>>
        +commit(commitTimestamp) void
        +rollback() void
    }

    class RecordStoreChange {
        -RecordStore* _rs
        -RecordId _recordId
        -ChangeType _type
        -string _oldData
        -string _newData
        +RecordStoreChange(rs, recordId, type, oldData, newData)
        +commit(commitTimestamp) void
        +rollback() void
    }

    class IndexChange {
        -SortedDataInterface* _interface
        -KeyString::Value _key
        -RecordId _recordId
        -ChangeType _type
        +IndexChange(interface, key, recordId, type)
        +commit(commitTimestamp) void
        +rollback() void
    }

    class OperationContext {
        -unique_ptr~RecoveryUnit~ _recoveryUnit
        -ServiceContext* _serviceContext
        -LogicalSessionId _lsid
        -TxnNumber _txnNumber
        -bool _inMultiDocumentTransaction
        -Timestamp _readTimestamp
        +getRecoveryUnit() RecoveryUnit*
        +setRecoveryUnit(ru, tokensToLinkFrom) void
        +writeConflictRetry(opStr, ns, f) auto
        +checkForInterrupt() void
        +getDeadline() Date_t
        +hasDeadline() bool
    }

    RecoveryUnit <|-- WiredTigerRecoveryUnit
    RecoveryUnit <|-- DevNullRecoveryUnit
    RecoveryUnit --> Change : manages
    Change <|-- RecordStoreChange
    Change <|-- IndexChange
    OperationContext --> RecoveryUnit : contains
    WiredTigerRecoveryUnit --> WiredTigerKVEngine : uses

2.4 索引存储层类图

classDiagram
    class SortedDataInterface {
        <<abstract>>
        +insertKeys(opCtx, keys, dupsAllowed) Status
        +removeKeys(opCtx, keys, dupsAllowed) void
        +unindex(opCtx, key, recordId, dupsAllowed) void
        +newCursor(opCtx, forward) unique_ptr~Cursor~
        +newRandomCursor(opCtx) unique_ptr~Cursor~
        +makeBulkBuilder(opCtx, dupsAllowed) unique_ptr~BulkBuilder~
        +truncate(opCtx) Status
        +isEmpty(opCtx) bool
        +getSpaceUsedBytes(opCtx) long long
        +getFreeStorageBytes(opCtx) long long
        +fullValidate(opCtx, keysOut, sizeOut) Status
        +dupKeyCheck(opCtx, key) Status
        +isUnique() bool
        +getKeyStringVersion() KeyString::Version
        +getOrdering() Ordering
    }

    class WiredTigerIndexUnique {
        -WiredTigerKVEngine* _kvEngine
        -string _uri
        -string _tableURI
        -KeyString::Version _keyStringVersion
        -Ordering _ordering
        -string _indexName
        -BSONObj _keyPattern
        -BSONObj _collation
        +WiredTigerIndexUnique(opCtx, uri, desc, keyFormat, isLogged)
        +insertKeys(opCtx, keys, dupsAllowed) Status
        +removeKeys(opCtx, keys, dupsAllowed) void
        +newCursor(opCtx, forward) unique_ptr~Cursor~
        +makeBulkBuilder(opCtx, dupsAllowed) unique_ptr~BulkBuilder~
        +isUnique() bool
        -_keyExists(opCtx, key) bool
        -_insertKey(opCtx, key, recordId) Status
        -_removeKey(opCtx, key, recordId) void
    }

    class WiredTigerIndexStandard {
        -WiredTigerKVEngine* _kvEngine
        -string _uri
        -string _tableURI
        -KeyString::Version _keyStringVersion
        -Ordering _ordering
        +WiredTigerIndexStandard(opCtx, uri, desc, keyFormat, isLogged)
        +insertKeys(opCtx, keys, dupsAllowed) Status
        +removeKeys(opCtx, keys, dupsAllowed) void
        +newCursor(opCtx, forward) unique_ptr~Cursor~
        +makeBulkBuilder(opCtx, dupsAllowed) unique_ptr~BulkBuilder~
        +isUnique() bool
    }

    class SortedDataBuilderInterface {
        <<abstract>>
        +addKey(key, recordId) Status
        +commit(dupsAllowed) Status
        +numKeys() int64_t
    }

    class WiredTigerIndexBulkBuilder {
        -WiredTigerKVEngine* _kvEngine
        -WT_SESSION* _session
        -WT_CURSOR* _cursor
        -string _uri
        -bool _dupsAllowed
        -int64_t _keysInserted
        -Ordering _ordering
        +WiredTigerIndexBulkBuilder(kvEngine, uri, dupsAllowed, ordering)
        +addKey(key, recordId) Status
        +commit(dupsAllowed) Status
        +numKeys() int64_t
        -_insertKey(key, recordId) Status
    }

    class SortedDataCursor {
        <<abstract>>
        +setEndPosition(endKey, endKeyInclusive) void
        +seek(key, requestedInfo) boost::optional~IndexKeyEntry~
        +seekForPrev(key, requestedInfo) boost::optional~IndexKeyEntry~
        +next(requestedInfo) boost::optional~IndexKeyEntry~
        +prev(requestedInfo) boost::optional~IndexKeyEntry~
        +save() void
        +restore() void
        +detachFromOperationContext() void
        +reattachToOperationContext(opCtx) void
    }

    class WiredTigerIndexCursor {
        -WT_CURSOR* _cursor
        -WiredTigerKVEngine* _kvEngine
        -string _uri
        -bool _forward
        -bool _positioned
        -Ordering _ordering
        -KeyString::Version _keyStringVersion
        +WiredTigerIndexCursor(kvEngine, uri, forward, ordering, keyStringVersion)
        +seek(key, requestedInfo) boost::optional~IndexKeyEntry~
        +next(requestedInfo) boost::optional~IndexKeyEntry~
        +save() void
        +restore() void
        -_getNext(requestedInfo) boost::optional~IndexKeyEntry~
        -_skipToNext() void
    }

    SortedDataInterface <|-- WiredTigerIndexUnique
    SortedDataInterface <|-- WiredTigerIndexStandard
    SortedDataInterface --> SortedDataBuilderInterface : creates
    SortedDataBuilderInterface <|-- WiredTigerIndexBulkBuilder
    SortedDataInterface --> SortedDataCursor : creates
    SortedDataCursor <|-- WiredTigerIndexCursor
    WiredTigerIndexUnique --> WiredTigerKVEngine : uses
    WiredTigerIndexStandard --> WiredTigerKVEngine : uses

2.5 目录管理层类图

classDiagram
    class KVCatalog {
        <<abstract>>
        +newEntry(opCtx, nss, ident, md) Status
        +putEntry(opCtx, nss, ident, md) Status
        +getEntry(nss) Entry
        +getAllEntries() vector~Entry~
        +dropEntry(opCtx, nss) Status
        +renameEntry(opCtx, fromNss, toNss, ident) Status
        +getIndexIdent(opCtx, nss, indexName) string
        +isCollectionIdent(ident) bool
        +isIndexIdent(ident) bool
        +getMetaData(opCtx, ns) BSONObj
        +setMetaData(opCtx, ns, md) Status
    }

    class WiredTigerCatalog {
        -WiredTigerKVEngine* _kvEngine
        -mutable Mutex _catalogLock
        -StringMap~Entry~ _catalog
        -string _catalogUri
        -bool _rand
        +WiredTigerCatalog(kvEngine, isLogged, isEphemeral, directoryPerDb)
        +init(opCtx) Status
        +newEntry(opCtx, nss, ident, md) Status
        +getEntry(nss) Entry
        +dropEntry(opCtx, nss) Status
        +getIndexIdent(opCtx, nss, indexName) string
        +isUserDataIdent(ident) bool
        +getMetaData(opCtx, ns) BSONObj
        +putMetaData(opCtx, ns, md) Status
        +getAllIdentsForDB(db) list~string~
        +getAllIdents() vector~string~
        -_loadCatalog(opCtx) Status
        -_saveCatalogToIndex(opCtx) Status
        -_generateNextIdent() string
    }

    class Entry {
        +string ident
        +BSONObj metadata
        +Entry()
        +Entry(ident, metadata)
    }

    class WiredTigerSizeStorer {
        -WiredTigerKVEngine* _kvEngine
        -string _uri
        -mutable Mutex _bufferMutex
        -map~string, SizeInfo~ _buffer
        -AtomicWord~long long~ _loadedFromDisk
        -unique_ptr~WiredTigerSession~ _session
        +WiredTigerSizeStorer(kvEngine, uri)
        +onCreate(uri, numRecords, dataSize) void
        +onDestroy(uri) void
        +store(uri, numRecords, dataSize) void
        +load(uri, numRecords, dataSize) void
        +flush() void
        +fillCache() void
        -_checkMagicNumber() void
        -_writeToBuffer(uri, numRecords, dataSize) void
    }

    class SizeInfo {
        +AtomicWord~long long~ numRecords
        +AtomicWord~long long~ dataSize
        +bool dirty
        +SizeInfo()
        +SizeInfo(numRecords, dataSize)
    }

    class WiredTigerDropPendingQueue {
        -mutable Mutex _mutex
        -condition_variable _condVar
        -bool _shuttingDown
        -list~WiredTigerDropPendingQueueEntry~ _dropPendingQueue
        +addDropPendingIdent(opTime, nss, ident) void
        +dropIdentsOlderThan(opCtx, ts) void
        +getAllDropPendingIdents() vector~string~
        +clearDropPendingState() void
        +getEarliestDropTimestamp() Timestamp
        -_dropIdent(opCtx, entry) void
    }

    KVCatalog <|-- WiredTigerCatalog
    WiredTigerCatalog --> Entry : manages
    WiredTigerCatalog --> WiredTigerKVEngine : uses
    WiredTigerKVEngine --> WiredTigerSizeStorer : uses
    WiredTigerSizeStorer --> SizeInfo : contains
    WiredTigerKVEngine --> WiredTigerDropPendingQueue : uses

3. 会话和连接管理

3.1 会话管理类图

classDiagram
    class WiredTigerSessionCache {
        -WiredTigerKVEngine* _engine
        -WT_CONNECTION* _conn
        -mutable Mutex _sessionsMutex
        -vector~WiredTigerSession*~ _sessions
        -size_t _maxSessions
        -AtomicWord~int~ _currentSessions
        -mutable Mutex _tableCacheMutex
        -StringMap~uint64_t~ _tableCreationTime
        +WiredTigerSessionCache(conn, engine)
        +getSession() WiredTigerSession*
        +releaseSession(session) void
        +closeAll() void
        +shuttingDown() void
        +snapshotManager() SnapshotManager*
        +isEphemeral() bool
        -_getSession(opCtx) WiredTigerSession*
        -_closeExpiredIdleSessions(idleExpireAfterSeconds) void
    }

    class WiredTigerSession {
        -WT_SESSION* _session
        -WiredTigerSessionCache* _cache
        -uint64_t _epoch
        -mutable Mutex _cursorsMutex
        -StringMap~WT_CURSOR*~ _cursors
        -int _cursorsOut
        -bool _idle
        +WiredTigerSession(conn, cache, epoch)
        +getSession() WT_SESSION*
        +getCursor(uri, overwrite, config) WT_CURSOR*
        +releaseCursor(id, cursor) void
        +closeCursor(uri) void
        +closeAllCursors() void
        +getIdleExpireTime() uint64_t
        +markIdle() void
        +markActive() void
        -_openCursor(uri, overwrite, config) WT_CURSOR*
    }

    class WiredTigerSnapshotManager {
        -WiredTigerKVEngine* _engine
        -WT_CONNECTION* _conn
        -mutable Mutex _mutex
        -bool _inShutdown
        -map~Timestamp, WT_SESSION*~ _committedSnapshots
        +WiredTigerSnapshotManager(engine, conn)
        +setCommittedSnapshot(timestamp) void
        +cleanupUnneededSnapshots() void
        +getMinSnapshotForNextCommittedRead() Timestamp
        +takeGlobalLock(opCtx) void
        +shutdown() void
        -_makeSnapshot(session, timestamp) void
    }

    class WiredTigerOplogManager {
        -WiredTigerKVEngine* _engine
        -unique_ptr~WiredTigerRecordStore~ _oplogRecordStore
        -mutable Mutex _oplogReadTimestampMutex
        -Timestamp _oplogMaxAtStartup
        -Timestamp _oplogReadTimestamp
        -AtomicWord~unsigned long long~ _oplogCounter
        +WiredTigerOplogManager(engine)
        +start(opCtx, oplogNS) void
        +halt() void
        +getOplogReadTimestamp() Timestamp
        +setOplogReadTimestamp(timestamp) void
        +getOplogMaxAtStartup() Timestamp
        +isRunning() bool
        -_oplogJournalThreadLoop() void
        -_updateOplogReadTimestamp(opCtx) void
    }

    WiredTigerKVEngine --> WiredTigerSessionCache : contains
    WiredTigerSessionCache --> WiredTigerSession : manages
    WiredTigerKVEngine --> WiredTigerSnapshotManager : uses
    WiredTigerKVEngine --> WiredTigerOplogManager : uses
    WiredTigerRecoveryUnit --> WiredTigerSession : uses

4. 存储特性和配置

4.1 存储配置类图

classDiagram
    class CollectionOptions {
        +bool capped
        +long long cappedSize
        +long long cappedMaxDocs
        +BSONObj storageEngine
        +BSONObj indexOptionDefaults
        +ValidationOptions validator
        +bool autoIndexId
        +BSONObj collation
        +boost::optional~UUID~ uuid
        +BSONObj encryptionInformation
        +CollectionOptions()
        +toBSON() BSONObj
        +fromBSON(obj) CollectionOptions
        +getStorageEngineOptions(engineName) BSONObj
    }

    class CappedCallback {
        <<abstract>>
        +aboutToDeleteCapped(opCtx, recordId, dataPtr) bool
        +cappedTruncateAfter(opCtx, recordId, inclusive) void
    }

    class RemoveSaver {
        -string _root
        -string _file
        -boost::filesystem::path _path
        -unique_ptr~boost::filesystem::ofstream~ _out
        +RemoveSaver(type, ns, why)
        +goingToDelete(obj) void
        +~RemoveSaver()
        -_findFileName() void
    }

    class IndexDescriptor {
        -BSONObj _keyPattern
        -BSONObj _infoObj
        -string _indexName
        -bool _isIdIndex
        -bool _isSparse
        -bool _isUnique
        -bool _isPartial
        -IndexVersion _version
        +IndexDescriptor(collection, accessMethodName, infoObj)
        +keyPattern() BSONObj
        +indexName() string
        +unique() bool
        +sparse() bool
        +partial() bool
        +getAccessMethodName() string
        +getEntry() IndexCatalogEntry*
        +areIndexOptionsEquivalent(other) bool
    }

    class WiredTigerKVEngineOptions {
        +bool directoryPerDB
        +bool journalCompressor
        +string engineConfig
        +string collectionConfig
        +string indexConfig
        +int cacheSizeGB
        +int maxCacheOverflowSizeGB
        +bool ephemeral
        +bool repair
        +WiredTigerKVEngineOptions()
        +setDirectoryPerDB(directoryPerDB) void
        +setCacheSizeGB(cacheSizeGB) void
        +getConfigString() string
    }

    class WiredTigerFileVersion {
        +enum Version
        +static const Version kLatestVersion
        +static hasStartupWarningsLogged() bool
        +static startupWarningsLogged() void
        +static shouldLog(warnType) bool
        +static getMinimumIndexVersion() IndexVersion
    }

    WiredTigerKVEngine --> CollectionOptions : uses
    RecordStore --> CappedCallback : uses
    WiredTigerKVEngine --> WiredTigerKVEngineOptions : configured by
    SortedDataInterface --> IndexDescriptor : uses
    WiredTigerKVEngine --> WiredTigerFileVersion : validates

5. 字段映射和约束

5.1 主要数据结构字段映射

数据结构	主要字段	数据类型	约束条件	说明
WiredTigerKVEngine	_conn	WT_CONNECTION*	非空	WiredTiger数据库连接
WiredTigerRecordStore	_tableURI	string	非空，格式"table:xxx"	WiredTiger表URI
RecordId	_id	int64_t	> 0或特殊值	记录唯一标识符
RecoveryUnit	_inUnitOfWork	bool	-	是否在事务中
WiredTigerSession	_session	WT_SESSION*	非空	WiredTiger会话句柄
CollectionOptions	cappedSize	long long	>= 0	固定集合大小限制

5.2 存储引擎约束

组件	约束类型	限制值	说明
WiredTiger	最大文档大小	16MB	单个BSON文档最大大小
WiredTiger	最大键长度	1024字节	索引键最大长度
WiredTiger	最大集合数	无限制	理论上无限制
RecordStore	固定集合大小	最小4KB	固定集合最小大小
Transaction	最大事务大小	256MB	单个事务最大修改数据量
SessionCache	最大会话数	1000	默认最大会话缓存数量

5.3 内存使用模式

组件	内存模式	默认大小	扩展策略
WiredTiger缓存	固定+动态	50%可用内存	自动调整
会话缓存	对象池	按需分配	LRU淘汰
游标缓存	线程本地	按需创建	生命周期管理
元数据缓存	固定大小	64MB	不扩展

MongoDB-09-存储引擎模块-数据结构#

1. 核心数据结构概览#

1.1 数据结构分类#

2. 核心类图#

2.1 存储引擎抽象层类图#

2.2 记录存储层类图#

2.3 事务管理层类图#

2.4 索引存储层类图#

2.5 目录管理层类图#

3. 会话和连接管理#

3.1 会话管理类图#

4. 存储特性和配置#

4.1 存储配置类图#

5. 字段映射和约束#

5.1 主要数据结构字段映射#

5.2 存储引擎约束#

5.3 内存使用模式#

MongoDB-09-存储引擎模块-数据结构

1. 核心数据结构概览

1.1 数据结构分类

2. 核心类图

2.1 存储引擎抽象层类图

2.2 记录存储层类图

2.3 事务管理层类图

2.4 索引存储层类图

2.5 目录管理层类图

3. 会话和连接管理

3.1 会话管理类图

4. 存储特性和配置

4.1 存储配置类图

5. 字段映射和约束

5.1 主要数据结构字段映射

5.2 存储引擎约束

5.3 内存使用模式