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database_impl.cpp
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database_impl.cpp
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/**
* Copyright (C) 2017 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kStorage
#include "mongo/platform/basic.h"
#include "mongo/db/catalog/database_impl.h"
#include <algorithm>
#include <boost/filesystem/operations.hpp>
#include <memory>
#include "mongo/base/init.h"
#include "mongo/db/audit.h"
#include "mongo/db/background.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/catalog/collection_catalog_entry.h"
#include "mongo/db/catalog/collection_options.h"
#include "mongo/db/catalog/database_catalog_entry.h"
#include "mongo/db/catalog/database_holder.h"
#include "mongo/db/catalog/drop_indexes.h"
#include "mongo/db/catalog/index_catalog.h"
#include "mongo/db/catalog/namespace_uuid_cache.h"
#include "mongo/db/catalog/uuid_catalog.h"
#include "mongo/db/clientcursor.h"
#include "mongo/db/commands/feature_compatibility_version_command_parser.h"
#include "mongo/db/concurrency/d_concurrency.h"
#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/curop.h"
#include "mongo/db/index/index_access_method.h"
#include "mongo/db/introspect.h"
#include "mongo/db/op_observer.h"
#include "mongo/db/query/collation/collator_factory_interface.h"
#include "mongo/db/repl/drop_pending_collection_reaper.h"
#include "mongo/db/repl/oplog.h"
#include "mongo/db/repl/replication_coordinator_global.h"
#include "mongo/db/s/operation_sharding_state.h"
#include "mongo/db/server_options.h"
#include "mongo/db/server_parameters.h"
#include "mongo/db/service_context.h"
#include "mongo/db/sessions_collection.h"
#include "mongo/db/stats/top.h"
#include "mongo/db/storage/recovery_unit.h"
#include "mongo/db/storage/storage_engine.h"
#include "mongo/db/storage/storage_options.h"
#include "mongo/db/system_index.h"
#include "mongo/db/views/view_catalog.h"
#include "mongo/platform/random.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/fail_point_service.h"
#include "mongo/util/log.h"
namespace mongo {
namespace {
//InitializeDatabaseFactory完成DatabaseImpl，真正在Database::makeImpl中执行
MONGO_INITIALIZER(InitializeDatabaseFactory)(InitializerContext* const) {
Database::registerFactory(
[](Database* const this_,
OperationContext* const opCtx,
const StringData name,
DatabaseCatalogEntry* const dbEntry) {
//真正在Database::makeImpl中执行
return stdx::make_unique<DatabaseImpl>(this_, opCtx, name, dbEntry);
}
);
return Status::OK();
}
MONGO_FP_DECLARE(hangBeforeLoggingCreateCollection);
} // namespace
using std::unique_ptr;
using std::endl;
using std::list;
using std::set;
using std::string;
using std::stringstream;
using std::vector;
//表中带有$的，不能做caller操作
void uassertNamespaceNotIndex(StringData ns, StringData caller) {
uassert(17320,
str::stream() << "cannot do " << caller << " on namespace with a $ in it: " << ns,
NamespaceString::normal(ns));
}
//DatabaseImpl::createCollection KVDatabaseCatalogEntryBase::createCollection中new该类
//该类结构最终保存在WiredTigerRecoveryUnit._changes
class DatabaseImpl::AddCollectionChange : public RecoveryUnit::Change {
public:
AddCollectionChange(OperationContext* opCtx, DatabaseImpl* db, StringData ns)
: _opCtx(opCtx), _db(db), _ns(ns.toString()) {}
virtual void commit() {
CollectionMap::const_iterator it = _db->_collections.find(_ns);
if (it == _db->_collections.end())
return;
// Ban reading from this collection on committed reads on snapshots before now.
auto replCoord = repl::ReplicationCoordinator::get(_opCtx);
auto snapshotName = replCoord->reserveSnapshotName(_opCtx);
it->second->setMinimumVisibleSnapshot(snapshotName);
}
virtual void rollback() {
CollectionMap::const_iterator it = _db->_collections.find(_ns);
if (it == _db->_collections.end())
return;
delete it->second;
_db->_collections.erase(it);
}
OperationContext* const _opCtx;
DatabaseImpl* const _db;
const std::string _ns;
};
class DatabaseImpl::RemoveCollectionChange : public RecoveryUnit::Change {
public:
// Takes ownership of coll (but not db).
RemoveCollectionChange(DatabaseImpl* db, Collection* coll) : _db(db), _coll(coll) {}
virtual void commit() {
delete _coll;
}
virtual void rollback() {
Collection*& inMap = _db->_collections[_coll->ns().ns()];
invariant(!inMap);
inMap = _coll;
}
DatabaseImpl* const _db;
Collection* const _coll;
};
DatabaseImpl::~DatabaseImpl() {
for (CollectionMap::const_iterator i = _collections.begin(); i != _collections.end(); ++i)
delete i->second;
}
//DatabaseHolderImpl::close调用
void DatabaseImpl::close(OperationContext* opCtx, const std::string& reason) {
// XXX? - Do we need to close database under global lock or just DB-lock is sufficient ?
invariant(opCtx->lockState()->isW());
// Clear cache of oplog Collection pointer.
repl::oplogCheckCloseDatabase(opCtx, this->_this);
if (BackgroundOperation::inProgForDb(_name)) {
log() << "warning: bg op in prog during close db? " << _name;
}
for (auto&& pair : _collections) {
auto* coll = pair.second;
coll->getCursorManager()->invalidateAll(opCtx, true, reason);
}
}
//库名有效性检查
Status DatabaseImpl::validateDBName(StringData dbname) {
if (dbname.size() <= 0)
return Status(ErrorCodes::BadValue, "db name is empty");
if (dbname.size() >= 64)
return Status(ErrorCodes::BadValue, "db name is too long");
if (dbname.find('.') != string::npos)
return Status(ErrorCodes::BadValue, "db name cannot contain a .");
if (dbname.find(' ') != string::npos)
return Status(ErrorCodes::BadValue, "db name cannot contain a space");
#ifdef _WIN32
static const char* windowsReservedNames[] = {
"con", "prn", "aux", "nul", "com1", "com2", "com3", "com4", "com5", "com6", "com7",
"com8", "com9", "lpt1", "lpt2", "lpt3", "lpt4", "lpt5", "lpt6", "lpt7", "lpt8", "lpt9"};
string lower(dbname.toString());
std::transform(lower.begin(), lower.end(), lower.begin(), ::tolower);
for (size_t i = 0; i < (sizeof(windowsReservedNames) / sizeof(char*)); ++i) {
if (lower == windowsReservedNames[i]) {
stringstream errorString;
errorString << "db name \"" << dbname.toString() << "\" is a reserved name";
return Status(ErrorCodes::BadValue, errorString.str());
}
}
#endif
return Status::OK();
}
//通过AutoGetCollection相关接口获取对应Collection，可以参考insertBatchAndHandleErrors
//初始化构造赋值见AutoGetCollection::AutoGetCollection,
//DatabaseImpl::_getOrCreateCollectionInstance AutoGetCollection::AutoGetCollection中调用获取collection
//DatabaseImpl::createCollection或者DatabaseImpl::init中调用_getOrCreateCollectionInstance真正生成collection信息
//查找collection类，找到直接返回，没找到构造一个新的collection类
//DatabaseImpl::createCollection DatabaseImpl::init 调用
Collection* DatabaseImpl::_getOrCreateCollectionInstance(OperationContext* opCtx,
const NamespaceString& nss) {
Collection* collection = getCollection(opCtx, nss);
if (collection) { //找到直接返回
return collection;
}
//DatabaseImpl._collections列表没用该collection，则从元数据_mdb_catalog.wt获取表信息
//没找到则构造一个新collection类
//KVDatabaseCatalogEntryBase::getCollectionCatalogEntry获取nss对应KVCollectionCatalogEntry
unique_ptr<CollectionCatalogEntry> cce(_dbEntry->getCollectionCatalogEntry(nss.ns()));
//获取uuid BSONCollectionCatalogEntry::getCollectionOptions
auto uuid = cce->getCollectionOptions(opCtx).uuid;
//KVDatabaseCatalogEntryBase::getRecordStore
//默认返回为StandardWiredTigerRecordStore类型
unique_ptr<RecordStore> rs(_dbEntry->getRecordStore(nss.ns()));
invariant(rs.get()); // if cce exists, so should this
// Not registering AddCollectionChange since this is for collections that already exist.
Collection* coll = new Collection(opCtx, nss.ns(), uuid, cce.release(), rs.release(), _dbEntry);
if (uuid) {
// We are not in a WUOW only when we are called from Database::init(). There is no need
// to rollback UUIDCatalog changes because we are initializing existing collections.
auto&& uuidCatalog = UUIDCatalog::get(opCtx);
if (!opCtx->lockState()->inAWriteUnitOfWork()) {
//UUIDCatalog::registerUUIDCatalogEntry
uuidCatalog.registerUUIDCatalogEntry(uuid.get(), coll);
} else {
//UUIDCatalog::onCreateCollection
uuidCatalog.onCreateCollection(opCtx, coll, uuid.get());
}
}
return coll;
}
//DatabaseHolderImpl::openDb中调用
DatabaseImpl::DatabaseImpl(Database* const this_,
OperationContext* const opCtx,
const StringData name,
DatabaseCatalogEntry* const dbEntry)
: _name(name.toString()),
_dbEntry(dbEntry),
_profileName(_name + ".system.profile"),
_indexesName(_name + ".system.indexes"),
_viewsName(_name + "." + DurableViewCatalog::viewsCollectionName().toString()),
_durableViews(DurableViewCatalogImpl(this_)),
_views(&_durableViews),
_this(this_) {}
//初始化构造Database类的时候就会调用该init，参考database.h中的explicit inline Database
void DatabaseImpl::init(OperationContext* const opCtx) {
Status status = validateDBName(_name);
if (!status.isOK()) {
warning() << "tried to open invalid db: " << _name;
uasserted(10028, status.toString());
}
_profile = serverGlobalParams.defaultProfile;
list<string> collections;
//KVDatabaseCatalogEntryBase::getCollectionNamespaces
//从元数据文件_mdb_catalog.wt中获取所有的表信息
_dbEntry->getCollectionNamespaces(&collections);
//把从原数据文件_mdb_catalog.wt获取到的表信息全部添加到_collections数组
for (list<string>::const_iterator it = collections.begin(); it != collections.end(); ++it) {
const string ns = *it;
NamespaceString nss(ns);
//collection初始化，生成对应CollectionImpl
_collections[ns] = _getOrCreateCollectionInstance(opCtx, nss);
}
// At construction time of the viewCatalog, the _collections map wasn't initialized yet, so no
// system.views collection would be found. Now we're sufficiently initialized, signal a version
// change. Also force a reload, so if there are problems with the catalog contents as might be
// caused by incorrect mongod versions or similar, they are found right away.
_views.invalidate();
Status reloadStatus = _views.reloadIfNeeded(opCtx);
if (!reloadStatus.isOK()) {
warning() << "Unable to parse views: " << redact(reloadStatus)
<< "; remove any invalid views from the " << _viewsName
<< " collection to restore server functionality." << startupWarningsLog;
}
}
//清除该库下面所有的临时表
void DatabaseImpl::clearTmpCollections(OperationContext* opCtx) {
invariant(opCtx->lockState()->isDbLockedForMode(name(), MODE_X));
list<string> collections;
_dbEntry->getCollectionNamespaces(&collections);
for (list<string>::iterator i = collections.begin(); i != collections.end(); ++i) {
string ns = *i;
invariant(NamespaceString::normal(ns));
CollectionCatalogEntry* coll = _dbEntry->getCollectionCatalogEntry(ns);
CollectionOptions options = coll->getCollectionOptions(opCtx);
//不是临时表
if (!options.temp)
continue;
//清除这个临时表
try {
WriteUnitOfWork wunit(opCtx);
Status status = dropCollection(opCtx, ns, {});
if (!status.isOK()) {
warning() << "could not drop temp collection '" << ns << "': " << redact(status);
continue;
}
wunit.commit();
} catch (const WriteConflictException&) {
warning() << "could not drop temp collection '" << ns << "' due to "
"WriteConflictException";
opCtx->recoveryUnit()->abandonSnapshot();
}
}
}
//db.setProfilingLevel(2)命令设置，参考https://docs.mongodb.com/v3.6/reference/method/db.setProfilingLevel/
//创建慢日志表system.profile并设置日志打印级别
Status DatabaseImpl::setProfilingLevel(OperationContext* opCtx, int newLevel) {
if (_profile == newLevel) {
return Status::OK();
}
if (newLevel == 0) {
_profile = 0;
return Status::OK();
}
if (newLevel < 0 || newLevel > 2) {
return Status(ErrorCodes::BadValue, "profiling level has to be >=0 and <= 2");
}
Status status = createProfileCollection(opCtx, this->_this);
if (!status.isOK()) {
return status;
}
_profile = newLevel;
return Status::OK();
}
//设置删库标记
void DatabaseImpl::setDropPending(OperationContext* opCtx, bool dropPending) {
invariant(opCtx->lockState()->isDbLockedForMode(name(), MODE_X));
if (dropPending) {
uassert(ErrorCodes::DatabaseDropPending,
str::stream() << "Unable to drop database " << name()
<< " because it is already in the process of being dropped.",
!_dropPending);
_dropPending = true;
} else {
_dropPending = false;
}
}
//该库是否正在被删除
bool DatabaseImpl::isDropPending(OperationContext* opCtx) const {
invariant(opCtx->lockState()->isDbLockedForMode(name(), MODE_X));
return _dropPending;
}
//db.stats统计
void DatabaseImpl::getStats(OperationContext* opCtx, BSONObjBuilder* output, double scale) {
list<string> collections;
_dbEntry->getCollectionNamespaces(&collections);
long long nCollections = 0;
long long nViews = 0;
long long objects = 0;
long long size = 0;
long long storageSize = 0;
long long numExtents = 0;
long long indexes = 0;
long long indexSize = 0;
for (list<string>::const_iterator it = collections.begin(); it != collections.end(); ++it) {
const string ns = *it;
Collection* collection = getCollection(opCtx, ns);
if (!collection)
continue;
nCollections += 1;
objects += collection->numRecords(opCtx);
size += collection->dataSize(opCtx);
BSONObjBuilder temp;
storageSize += collection->getRecordStore()->storageSize(opCtx, &temp);
numExtents += temp.obj()["numExtents"].numberInt(); // XXX
indexes += collection->getIndexCatalog()->numIndexesTotal(opCtx);
indexSize += collection->getIndexSize(opCtx);
}
getViewCatalog()->iterate(opCtx, [&](const ViewDefinition& view) { nViews += 1; });
output->appendNumber("collections", nCollections);
output->appendNumber("views", nViews);
output->appendNumber("objects", objects);
output->append("avgObjSize", objects == 0 ? 0 : double(size) / double(objects));
output->appendNumber("dataSize", size / scale);
output->appendNumber("storageSize", storageSize / scale);
output->appendNumber("numExtents", numExtents);
output->appendNumber("indexes", indexes);
output->appendNumber("indexSize", indexSize / scale);
_dbEntry->appendExtraStats(opCtx, output, scale);
if (!opCtx->getServiceContext()->getGlobalStorageEngine()->isEphemeral()) {
boost::filesystem::path dbpath(storageGlobalParams.dbpath);
if (storageGlobalParams.directoryperdb) {
dbpath /= _name;
}
boost::system::error_code ec;
boost::filesystem::space_info spaceInfo = boost::filesystem::space(dbpath, ec);
if (!ec) {
output->appendNumber("fsUsedSize", (spaceInfo.capacity - spaceInfo.available) / scale);
output->appendNumber("fsTotalSize", spaceInfo.capacity / scale);
} else {
output->appendNumber("fsUsedSize", -1);
output->appendNumber("fsTotalSize", -1);
log() << "Failed to query filesystem disk stats (code: " << ec.value()
<< "): " << ec.message();
}
}
}
//view相关，先跳过，以后有空再分析
Status DatabaseImpl::dropView(OperationContext* opCtx, StringData fullns) {
Status status = _views.dropView(opCtx, NamespaceString(fullns));
Top::get(opCtx->getServiceContext()).collectionDropped(fullns);
return status;
}
//drop删表CmdDrop::errmsgRun->dropCollection会调用
//DatabaseImpl::clearTmpCollections调用
Status DatabaseImpl::dropCollection(OperationContext* opCtx,
StringData fullns,
repl::OpTime dropOpTime) {
//删除一个不存在的表直接当成功处理
if (!getCollection(opCtx, fullns)) {
// Collection doesn't exist so don't bother validating if it can be dropped.
return Status::OK();
}
NamespaceString nss(fullns);
{
//确定要删除的表是否属于该db库
verify(nss.db() == _name);
if (nss.isSystem()) {
//system.profile日志表删除前必须关闭日志profile记录
if (nss.isSystemDotProfile()) {
if (_profile != 0)
return Status(ErrorCodes::IllegalOperation,
"turn off profiling before dropping system.profile collection");
} else if (!(nss.isSystemDotViews() || nss.isHealthlog() ||
nss == SessionsCollection::kSessionsNamespaceString ||
nss == NamespaceString::kSystemKeysCollectionName)) {
//这几个system.xx以外的系统表不允许删除
return Status(ErrorCodes::IllegalOperation,
str::stream() << "can't drop system collection " << fullns);
}
}
}
return dropCollectionEvenIfSystem(opCtx, nss, dropOpTime);
}
//drop删表CmdDrop::errmsgRun->dropCollection->DatabaseImpl::dropCollectionEvenIfSystem
////drop删表CmdDrop::errmsgRun->dropCollection会调用
Status DatabaseImpl::dropCollectionEvenIfSystem(OperationContext* opCtx,
const NamespaceString& fullns,
repl::OpTime dropOpTime) {
invariant(opCtx->lockState()->isDbLockedForMode(name(), MODE_X));
LOG(1) << "dropCollection: " << fullns;
// A valid 'dropOpTime' is not allowed when writes are replicated.
if (!dropOpTime.isNull() && opCtx->writesAreReplicated()) {
return Status(
ErrorCodes::BadValue,
"dropCollection() cannot accept a valid drop optime when writes are replicated.");
}
//获取表信息
Collection* collection = getCollection(opCtx, fullns);
//表本来就不存在，直接返回OK
if (!collection) {
return Status::OK(); // Post condition already met.
}
//获取表对应uuid
auto uuid = collection->uuid();
auto uuidString = uuid ? uuid.get().toString() : "no UUID";
//$命名的表不能做删表操作
uassertNamespaceNotIndex(fullns.toString(), "dropCollection");
//正在后台加索引的表不能删除
BackgroundOperation::assertNoBgOpInProgForNs(fullns);
// Make sure no indexes builds are in progress.
// Use massert() to be consistent with IndexCatalog::dropAllIndexes().
auto numIndexesInProgress = collection->getIndexCatalog()->numIndexesInProgress(opCtx);
massert(40461,
str::stream() << "cannot drop collection " << fullns.ns() << " (" << uuidString
<< ") when "
<< numIndexesInProgress
<< " index builds in progress.",
numIndexesInProgress == 0);
//审计日志
audit::logDropCollection(&cc(), fullns.toString());
//删表后，需要清空该表的统计信息，从usage中移除
Top::get(opCtx->getServiceContext()).collectionDropped(fullns.toString());
// Drop unreplicated collections immediately.
// If 'dropOpTime' is provided, we should proceed to rename the collection.
// Under master/slave, collections are always dropped immediately. This is because drop-pending
// collections support the rollback process which is not applicable to master/slave.
auto replCoord = repl::ReplicationCoordinator::get(opCtx);
auto opObserver = opCtx->getServiceContext()->getOpObserver();
//一般表都是false
auto isOplogDisabledForNamespace = replCoord->isOplogDisabledFor(opCtx, fullns);
//不是复制集方式启动
auto isMasterSlave =
repl::ReplicationCoordinator::modeMasterSlave == replCoord->getReplicationMode();
//master slave方式启动
if ((dropOpTime.isNull() && isOplogDisabledForNamespace) || isMasterSlave) {
//真正的底层WT存储引擎相关表及其索引删除在这里
auto status = _finishDropCollection(opCtx, fullns, collection);
if (!status.isOK()) {
return status;
}
//OpObserverImpl::onDropCollection
opObserver->onDropCollection(opCtx, fullns, uuid);
return Status::OK();
}
// Replicated collections will be renamed with a special drop-pending namespace and dropped when
// the replica set optime reaches the drop optime.
if (dropOpTime.isNull()) {
// MMAPv1 requires that index namespaces are subject to the same length constraints as
// indexes in collections that are not in a drop-pending state. Therefore, we check if the
// drop-pending namespace is too long for any index names in the collection.
// These indexes are dropped regardless of the storage engine on the current node because we
// may still have nodes running MMAPv1 in the replica set.
// Compile a list of any indexes that would become too long following the drop-pending
// rename. In the case that this collection drop gets rolled back, this will incur a
// performance hit, since those indexes will have to be rebuilt from scratch, but data
// integrity is maintained.
//获取该集合对应的索引信息
std::vector<IndexDescriptor*> indexesToDrop;
//索引迭代器
auto indexIter = collection->getIndexCatalog()->getIndexIterator(opCtx, true);
// Determine which index names are too long. Since we don't have the collection drop optime
// at this time, use the maximum optime to check the index names.
auto longDpns = fullns.makeDropPendingNamespace(repl::OpTime::max());
//获取该表下面的所有索引信息长度超标的索引，存入indexesToDrop数组容器
while (indexIter.more()) {
auto index = indexIter.next();
//只记录长度超限的索引，这类索引需要提前删除
//其他的没有超限的索引在_finishDropCollection中的IndexCatalogImpl::dropAllIndexes删除
auto status = longDpns.checkLengthForRename(index->indexName().size());
if (!status.isOK()) {
indexesToDrop.push_back(index);
}
}
// Drop the offending indexes.
for (auto&& index : indexesToDrop) {
log() << "dropCollection: " << fullns << " (" << uuidString << ") - index namespace '"
<< index->indexNamespace()
<< "' would be too long after drop-pending rename. Dropping index immediately.";
//IndexCatalogImpl::dropIndex 删除索引
fassertStatusOK(40463, collection->getIndexCatalog()->dropIndex(opCtx, index));
//OpObserverImpl::onDropIndex 该索引删除对应的oplog记录，用于主从同步
opObserver->onDropIndex(
opCtx, fullns, collection->uuid(), index->indexName(), index->infoObj());
}
// Log oplog entry for collection drop and proceed to complete rest of two phase drop
// process.
//OpObserverImpl::onDropCollection 删表对应的oplog记录，用于主从同步
dropOpTime = opObserver->onDropCollection(opCtx, fullns, uuid);
// Drop collection immediately if OpObserver did not write entry to oplog.
// After writing the oplog entry, all errors are fatal. See getNextOpTime() comments in
// oplog.cpp.
if (dropOpTime.isNull()) {
log() << "dropCollection: " << fullns << " (" << uuidString
<< ") - no drop optime available for pending-drop. "
<< "Dropping collection immediately.";
//这里进行底层
fassertStatusOK(40462, _finishDropCollection(opCtx, fullns, collection));
return Status::OK();
}
} else {
// If we are provided with a valid 'dropOpTime', it means we are dropping this collection
// in the context of applying an oplog entry on a secondary.
// OpObserver::onDropCollection() should be returning a null OpTime because we should not be
// writing to the oplog.
//OpObserver::onDropCollection
auto opTime = opObserver->onDropCollection(opCtx, fullns, uuid);
if (!opTime.isNull()) {
severe() << "dropCollection: " << fullns << " (" << uuidString
<< ") - unexpected oplog entry written to the oplog with optime " << opTime;
fassertFailed(40468);
}
}
auto dpns = fullns.makeDropPendingNamespace(dropOpTime);
// Rename collection using drop-pending namespace generated from drop optime.
const bool stayTemp = true;
log() << "dropCollection: " << fullns << " (" << uuidString
<< ") - renaming to drop-pending collection: " << dpns << " with drop optime "
<< dropOpTime;
fassertStatusOK(40464, renameCollection(opCtx, fullns.ns(), dpns.ns(), stayTemp));
// Register this drop-pending namespace with DropPendingCollectionReaper to remove when the
// committed optime reaches the drop optime.
repl::DropPendingCollectionReaper::get(opCtx)->addDropPendingNamespace(dropOpTime, dpns);
return Status::OK();
}
//drop删表CmdDrop::errmsgRun->dropCollection->DatabaseImpl::dropCollectionEvenIfSystem->DatabaseImpl::_finishDropCollection
// ->DatabaseImpl::_finishDropCollection
//真正的底层WT存储引擎相关表及其索引删除在这里
Status DatabaseImpl::_finishDropCollection(OperationContext* opCtx,
const NamespaceString& fullns,
Collection* collection) {
LOG(1) << "dropCollection: " << fullns << " - dropAllIndexes start";
//先删除表下的所有索引
//IndexCatalogImpl::dropAllIndexes
collection->getIndexCatalog()->dropAllIndexes(opCtx, true);
invariant(collection->getCatalogEntry()->getTotalIndexCount(opCtx) == 0);
LOG(1) << "dropCollection: " << fullns << " - dropAllIndexes done";
// We want to destroy the Collection object before telling the StorageEngine to destroy the
// RecordStore.
////从DatabaseImpl._collections集合中把删除的集合去掉，以后就不能通过DatabaseImpl找到该集合了
_clearCollectionCache(
opCtx, fullns.toString(), "collection dropped", /*collectionGoingAway*/ true);
//获取集合uuid
auto uuid = collection->uuid();
auto uuidString = uuid ? uuid.get().toString() : "no UUID";
log() << "Finishing collection drop for " << fullns << " (" << uuidString << ").";
//KVDatabaseCatalogEntry::dropCollection
//真正的表文件相关底层删除在这里
return _dbEntry->dropCollection(opCtx, fullns.toString());
}
//drop删表CmdDrop::errmsgRun->dropCollection->DatabaseImpl::dropCollectionEvenIfSystem->DatabaseImpl::_finishDropCollection
//DatabaseImpl::_finishDropCollection中调用
//从DatabaseImpl._collections集合中把删除的集合去掉，以后就不能通过DatabaseImpl找到该集合了
void DatabaseImpl::_clearCollectionCache(OperationContext* opCtx,
StringData fullns,
const std::string& reason,
bool collectionGoingAway) {
verify(_name == nsToDatabaseSubstring(fullns));
CollectionMap::const_iterator it = _collections.find(fullns.toString());
if (it == _collections.end())
return;
// Takes ownership of the collection
opCtx->recoveryUnit()->registerChange(new RemoveCollectionChange(this, it->second));
it->second->getCursorManager()->invalidateAll(opCtx, collectionGoingAway, reason);
_collections.erase(it);
}
//DatabaseImpl::_getOrCreateCollectionInstance AutoGetCollection::AutoGetCollection中调用
Collection* DatabaseImpl::getCollection(OperationContext* opCtx, StringData ns) const {
NamespaceString nss(ns);
invariant(_name == nss.db());
return getCollection(opCtx, nss);
}
//DatabaseImpl::_getOrCreateCollectionInstance AutoGetCollection::AutoGetCollection中调用
//从_collections缓存中找出nss对应的表，DatabaseImpl::createCollection创建collection的时候添加到_collections数组
Collection* DatabaseImpl::getCollection(OperationContext* opCtx, const NamespaceString& nss) const {
dassert(!cc().getOperationContext() || opCtx == cc().getOperationContext());
CollectionMap::const_iterator it = _collections.find(nss.ns());
if (it != _collections.end() && it->second) {
Collection* found = it->second;
if (enableCollectionUUIDs) {
//更新NamespaceUUIDCache
NamespaceUUIDCache& cache = NamespaceUUIDCache::get(opCtx);
if (auto uuid = found->uuid())
cache.ensureNamespaceInCache(nss, uuid.get());
}
return found;
}
return NULL;
}
//集合重命名
Status DatabaseImpl::renameCollection(OperationContext* opCtx,
StringData fromNS,
StringData toNS,
bool stayTemp) {
//审计相关
audit::logRenameCollection(&cc(), fromNS, toNS);
invariant(opCtx->lockState()->isDbLockedForMode(name(), MODE_X));
BackgroundOperation::assertNoBgOpInProgForNs(fromNS);
BackgroundOperation::assertNoBgOpInProgForNs(toNS);
NamespaceString fromNSS(fromNS);
NamespaceString toNSS(toNS);
{ // remove anything cached
//查找该db下面是否有该collection
Collection* coll = getCollection(opCtx, fromNS);
if (!coll)
return Status(ErrorCodes::NamespaceNotFound, "collection not found to rename");
string clearCacheReason = str::stream() << "renamed collection '" << fromNS << "' to '"
<< toNS << "'";
IndexCatalog::IndexIterator ii = coll->getIndexCatalog()->getIndexIterator(opCtx, true);
while (ii.more()) {
IndexDescriptor* desc = ii.next();
_clearCollectionCache(
opCtx, desc->indexNamespace(), clearCacheReason, /*collectionGoingAway*/ true);
}
//从db中清除from和to的collection信息
_clearCollectionCache(opCtx, fromNS, clearCacheReason, /*collectionGoingAway*/ true);
_clearCollectionCache(opCtx, toNS, clearCacheReason, /*collectionGoingAway*/ false);
//统计中清除from集合
Top::get(opCtx->getServiceContext()).collectionDropped(fromNS.toString());
}
//KVDatabaseCatalogEntry::renameCollection 存储引擎层从命名集合
Status s = _dbEntry->renameCollection(opCtx, fromNS, toNS, stayTemp);
opCtx->recoveryUnit()->registerChange(new AddCollectionChange(opCtx, this, toNS));
//新的集合名添加到_collections[]数组
_collections[toNS] = _getOrCreateCollectionInstance(opCtx, toNSS);
return s;
}
//获取collection信息，没用则创建
Collection* DatabaseImpl::getOrCreateCollection(OperationContext* opCtx,
const NamespaceString& nss) {
Collection* c = getCollection(opCtx, nss);
if (!c) {
c = createCollection(opCtx, nss.ns());
}
return c;
}
//检测是否可以创建集合
void DatabaseImpl::_checkCanCreateCollection(OperationContext* opCtx,
const NamespaceString& nss,
const CollectionOptions& options) {
massert(17399,
str::stream() << "Cannot create collection " << nss.ns()
<< " - collection already exists.",
getCollection(opCtx, nss) == nullptr);
uassertNamespaceNotIndex(nss.ns(), "createCollection");
uassert(14037,
"can't create user databases on a --configsvr instance",
serverGlobalParams.clusterRole != ClusterRole::ConfigServer || nss.isOnInternalDb());
// This check only applies for actual collections, not indexes or other types of ns.
uassert(17381,
str::stream() << "fully qualified namespace " << nss.ns() << " is too long "
<< "(max is "
<< NamespaceString::MaxNsCollectionLen
<< " bytes)",
!nss.isNormal() || nss.size() <= NamespaceString::MaxNsCollectionLen);
uassert(17316, "cannot create a blank collection", nss.coll() > 0);
uassert(28838, "cannot create a non-capped oplog collection", options.capped || !nss.isOplog());
uassert(ErrorCodes::DatabaseDropPending,
str::stream() << "Cannot create collection " << nss.ns()
<< " - database is in the process of being dropped.",
!_dropPending);
}
Status DatabaseImpl::createView(OperationContext* opCtx,
StringData ns,
const CollectionOptions& options) {
invariant(opCtx->lockState()->isDbLockedForMode(name(), MODE_X));
invariant(options.isView());
NamespaceString nss(ns);
NamespaceString viewOnNss(nss.db(), options.viewOn);
_checkCanCreateCollection(opCtx, nss, options);
audit::logCreateCollection(&cc(), ns);
if (nss.isOplog())
return Status(ErrorCodes::InvalidNamespace,
str::stream() << "invalid namespace name for a view: " + nss.toString());
return _views.createView(opCtx, nss, viewOnNss, BSONArray(options.pipeline), options.collation);
}
//AutoGetDb::AutoGetDb或者AutoGetOrCreateDb::AutoGetOrCreateDb->DatabaseHolderImpl::get从DatabaseHolderImpl._dbs数组查找获取Database
//DatabaseImpl::createCollection创建collection的表全部添加到_collections数组中
//AutoGetCollection::AutoGetCollection从UUIDCatalog._catalog数组通过查找uuid可以获取collection表信息
//手动建表流程：CmdCreate::run->createCollection->mongo::userCreateNSImpl->
//直接写入数据的时候会建表流程：insertBatchAndHandleErrors->makeCollection->mongo::userCreateNS
// ->mongo::userCreateNSImpl->DatabaseImpl::createCollection
//insertBatchAndHandleErrors->makeCollection->mongo::userCreateNS->mongo::userCreateNSImpl->DatabaseImpl::createCollection
//在wiredtiger创建集合和索引
Collection* DatabaseImpl::createCollection(OperationContext* opCtx,
StringData ns,
const CollectionOptions& options,
bool createIdIndex,
const BSONObj& idIndex) {
//注意这里检查锁，建集合必须是MODE_X锁
invariant(opCtx->lockState()->isDbLockedForMode(name(), MODE_X));
invariant(!options.isView());
NamespaceString nss(ns);
//是否允许隐式创建集合
uassert(ErrorCodes::CannotImplicitlyCreateCollection,
"request doesn't allow collection to be created implicitly",
OperationShardingState::get(opCtx).allowImplicitCollectionCreation());
CollectionOptions optionsWithUUID = options;
bool generatedUUID = false;
//默认开启
//每个collection会对应一个uuid，见DatabaseImpl::createCollection，只有3.6以上版本有该uuid
if (enableCollectionUUIDs && !optionsWithUUID.uuid &&
serverGlobalParams.featureCompatibility.isSchemaVersion36()) {
auto coordinator = repl::ReplicationCoordinator::get(opCtx);
bool fullyUpgraded = serverGlobalParams.featureCompatibility.getVersion() ==
ServerGlobalParams::FeatureCompatibility::Version::kFullyUpgradedTo36;
bool canGenerateUUID =
//单机方式启动
(coordinator->getReplicationMode() != repl::ReplicationCoordinator::modeReplSet) ||
//复制集方式，是否可以写，如果主在就可以 或者 慢日志表
coordinator->canAcceptWritesForDatabase(opCtx, nss.db()) || nss.isSystemDotProfile();
if (fullyUpgraded && !canGenerateUUID) {
std::string msg = str::stream() << "Attempted to create a new collection " << nss.ns()
<< " without a UUID";
severe() << msg;
uasserted(ErrorCodes::InvalidOptions, msg);
}
//每个表对应一个uuid
if (canGenerateUUID) {
//也就是UUID::gen()，生成唯一UUID
optionsWithUUID.uuid.emplace(CollectionUUID::gen());
generatedUUID = true;
}
}
//检查相关参数是否有效，如集合名最大长度等
_checkCanCreateCollection(opCtx, nss, optionsWithUUID);
audit::logCreateCollection(&cc(), ns);
//createCollection: test.test with generated UUID: 43e959f4-7bb4-4cd1-ba10-5075df67fa44
if (optionsWithUUID.uuid) {
log() << "createCollection: " << ns << " with "
<< (generatedUUID ? "generated" : "provided")
<< " UUID: " << optionsWithUUID.uuid.get(); //OptionalCollectionUUID
} else {
log() << "createCollection: " << ns << " with no UUID.";
}
//KVDatabaseCatalogEntryBase::createCollection
//通知wiredtiger创建collection对应的目录文件
massertStatusOK(
//对应KVDatabaseCatalogEntryBase::createCollection
//调用KV层的元数据管理模块
_dbEntry->createCollection(opCtx, ns, optionsWithUUID, true /*allocateDefaultSpace*/));
//wiredtiger对应WiredTigerRecoveryUnit::registerChange
opCtx->recoveryUnit()->registerChange(new AddCollectionChange(opCtx, this, ns));
//查找collection类，找到直接返回，没找到构造一个新的collection类
Collection* collection = _getOrCreateCollectionInstance(opCtx, nss);
invariant(collection);
//保存到_collections数组
_collections[ns] = collection; //ns集合对应collection
BSONObj fullIdIndexSpec;
//id索引创建
if (createIdIndex) {
if (collection->requiresIdIndex()) {
if (optionsWithUUID.autoIndexId == CollectionOptions::YES ||
optionsWithUUID.autoIndexId == CollectionOptions::DEFAULT) {
const auto featureCompatibilityVersion =
serverGlobalParams.featureCompatibility.getVersion();
IndexCatalog* ic = collection->getIndexCatalog();
//IndexCatalogImpl::createIndexOnEmptyCollection
//建id索引
fullIdIndexSpec = uassertStatusOK(ic->createIndexOnEmptyCollection(
opCtx,
!idIndex.isEmpty() ? idIndex
: ic->getDefaultIdIndexSpec(featureCompatibilityVersion)));
}
}
//如锅集合是"system.X"相关的索引
if (nss.isSystem()) { //wiredtiger创建普通索引文件
createSystemIndexes(opCtx, collection);
}
}
MONGO_FAIL_POINT_PAUSE_WHILE_SET(hangBeforeLoggingCreateCollection);
opCtx->getServiceContext()->getOpObserver()->onCreateCollection(
opCtx, collection, nss, optionsWithUUID, fullIdIndexSpec);
return collection;
}
const DatabaseCatalogEntry* DatabaseImpl::getDatabaseCatalogEntry() const {
return _dbEntry;
}
//drop_database.cpp中的dropDatabase和DatabaseImpl::dropDatabase dropDatabaseImpl什么区别？需要进一步分析
//区别如下：drop_database.cpp中的dropDatabase会通过_finishDropDatabase调用DatabaseImpl::dropDatabase
//drop_database.cpp中的dropDatabase删库及其库下面的表，DatabaseImpl::dropDatabase只删库
//删库dropDatabase->_finishDropDatabase调用
void DatabaseImpl::dropDatabase(OperationContext* opCtx, Database* db) {
invariant(db);
// Store the name so we have if for after the db object is deleted
const string name = db->name();
LOG(1) << "dropDatabase " << name;
invariant(opCtx->lockState()->isDbLockedForMode(name, MODE_X));
//检查是否有在创建后台索引等
BackgroundOperation::assertNoBgOpInProgForDb(name);
audit::logDropDatabase(opCtx->getClient(), name);