/lib/Doctrine/ODM/MongoDB/UnitOfWork.php

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<?php

declare(strict_types=1);

namespace Doctrine\ODM\MongoDB;

use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\Common\EventManager;
use Doctrine\Common\NotifyPropertyChanged;
use Doctrine\Common\PropertyChangedListener;
use Doctrine\ODM\MongoDB\Hydrator\HydratorFactory;
use Doctrine\ODM\MongoDB\Mapping\ClassMetadata;
use Doctrine\ODM\MongoDB\Mapping\MappingException;
use Doctrine\ODM\MongoDB\PersistentCollection\PersistentCollectionException;
use Doctrine\ODM\MongoDB\PersistentCollection\PersistentCollectionInterface;
use Doctrine\ODM\MongoDB\Persisters\CollectionPersister;
use Doctrine\ODM\MongoDB\Persisters\PersistenceBuilder;
use Doctrine\ODM\MongoDB\Query\Query;
use Doctrine\ODM\MongoDB\Types\DateType;
use Doctrine\ODM\MongoDB\Types\Type;
use Doctrine\ODM\MongoDB\Utility\CollectionHelper;
use Doctrine\ODM\MongoDB\Utility\LifecycleEventManager;
use InvalidArgumentException;
use MongoDB\BSON\UTCDateTime;
use ProxyManager\Proxy\GhostObjectInterface;
use UnexpectedValueException;
use function array_filter;
use function count;
use function get_class;
use function in_array;
use function is_array;
use function is_object;
use function method_exists;
use function preg_match;
use function serialize;
use function spl_object_hash;
use function sprintf;

/**
 * The UnitOfWork is responsible for tracking changes to objects during an
 * "object-level" transaction and for writing out changes to the database
 * in the correct order.
 */
final class UnitOfWork implements PropertyChangedListener
{
    /**
     * A document is in MANAGED state when its persistence is managed by a DocumentManager.
     */
    public const STATE_MANAGED = 1;

    /**
     * A document is new if it has just been instantiated (i.e. using the "new" operator)
     * and is not (yet) managed by a DocumentManager.
     */
    public const STATE_NEW = 2;

    /**
     * A detached document is an instance with a persistent identity that is not
     * (or no longer) associated with a DocumentManager (and a UnitOfWork).
     */
    public const STATE_DETACHED = 3;

    /**
     * A removed document instance is an instance with a persistent identity,
     * associated with a DocumentManager, whose persistent state has been
     * deleted (or is scheduled for deletion).
     */
    public const STATE_REMOVED = 4;

    /**
     * The identity map holds references to all managed documents.
     *
     * Documents are grouped by their class name, and then indexed by the
     * serialized string of their database identifier field or, if the class
     * has no identifier, the SPL object hash. Serializing the identifier allows
     * differentiation of values that may be equal (via type juggling) but not
     * identical.
     *
     * Since all classes in a hierarchy must share the same identifier set,
     * we always take the root class name of the hierarchy.
     *
     * @var array
     */
    private $identityMap = [];

    /**
     * Map of all identifiers of managed documents.
     * Keys are object ids (spl_object_hash).
     *
     * @var array
     */
    private $documentIdentifiers = [];

    /**
     * Map of the original document data of managed documents.
     * Keys are object ids (spl_object_hash). This is used for calculating changesets
     * at commit time.
     *
     * @internal Note that PHPs "copy-on-write" behavior helps a lot with memory usage.
     *           A value will only really be copied if the value in the document is modified
     *           by the user.
     *
     * @var array
     */
    private $originalDocumentData = [];

    /**
     * Map of document changes. Keys are object ids (spl_object_hash).
     * Filled at the beginning of a commit of the UnitOfWork and cleaned at the end.
     *
     * @var array
     */
    private $documentChangeSets = [];

    /**
     * The (cached) states of any known documents.
     * Keys are object ids (spl_object_hash).
     *
     * @var array
     */
    private $documentStates = [];

    /**
     * Map of documents that are scheduled for dirty checking at commit time.
     *
     * Documents are grouped by their class name, and then indexed by their SPL
     * object hash. This is only used for documents with a change tracking
     * policy of DEFERRED_EXPLICIT.
     *
     * @var array
     */
    private $scheduledForSynchronization = [];

    /**
     * A list of all pending document insertions.
     *
     * @var array
     */
    private $documentInsertions = [];

    /**
     * A list of all pending document updates.
     *
     * @var array
     */
    private $documentUpdates = [];

    /**
     * A list of all pending document upserts.
     *
     * @var array
     */
    private $documentUpserts = [];

    /**
     * A list of all pending document deletions.
     *
     * @var array
     */
    private $documentDeletions = [];

    /**
     * All pending collection deletions.
     *
     * @var array
     */
    private $collectionDeletions = [];

    /**
     * All pending collection updates.
     *
     * @var array
     */
    private $collectionUpdates = [];

    /**
     * A list of documents related to collections scheduled for update or deletion
     *
     * @var array
     */
    private $hasScheduledCollections = [];

    /**
     * List of collections visited during changeset calculation on a commit-phase of a UnitOfWork.
     * At the end of the UnitOfWork all these collections will make new snapshots
     * of their data.
     *
     * @var array
     */
    private $visitedCollections = [];

    /**
     * The DocumentManager that "owns" this UnitOfWork instance.
     *
     * @var DocumentManager
     */
    private $dm;

    /**
     * The EventManager used for dispatching events.
     *
     * @var EventManager
     */
    private $evm;

    /**
     * Additional documents that are scheduled for removal.
     *
     * @var array
     */
    private $orphanRemovals = [];

    /**
     * The HydratorFactory used for hydrating array Mongo documents to Doctrine object documents.
     *
     * @var HydratorFactory
     */
    private $hydratorFactory;

    /**
     * The document persister instances used to persist document instances.
     *
     * @var array
     */
    private $persisters = [];

    /**
     * The collection persister instance used to persist changes to collections.
     *
     * @var Persisters\CollectionPersister
     */
    private $collectionPersister;

    /**
     * The persistence builder instance used in DocumentPersisters.
     *
     * @var PersistenceBuilder|null
     */
    private $persistenceBuilder;

    /**
     * Array of parent associations between embedded documents.
     *
     * @var array
     */
    private $parentAssociations = [];

    /** @var LifecycleEventManager */
    private $lifecycleEventManager;

    /**
     * Array of embedded documents known to UnitOfWork. We need to hold them to prevent spl_object_hash
     * collisions in case already managed object is lost due to GC (so now it won't). Embedded documents
     * found during doDetach are removed from the registry, to empty it altogether clear() can be utilized.
     *
     * @var array
     */
    private $embeddedDocumentsRegistry = [];

    /** @var int */
    private $commitsInProgress = 0;

    /**
     * Initializes a new UnitOfWork instance, bound to the given DocumentManager.
     */
    public function __construct(DocumentManager $dm, EventManager $evm, HydratorFactory $hydratorFactory)
    {
        $this->dm                    = $dm;
        $this->evm                   = $evm;
        $this->hydratorFactory       = $hydratorFactory;
        $this->lifecycleEventManager = new LifecycleEventManager($dm, $this, $evm);
    }

    /**
     * Factory for returning new PersistenceBuilder instances used for preparing data into
     * queries for insert persistence.
     *
     * @internal
     */
    public function getPersistenceBuilder() : PersistenceBuilder
    {
        if (! $this->persistenceBuilder) {
            $this->persistenceBuilder = new PersistenceBuilder($this->dm, $this);
        }

        return $this->persistenceBuilder;
    }

    /**
     * Sets the parent association for a given embedded document.
     *
     * @internal
     */
    public function setParentAssociation(object $document, array $mapping, ?object $parent, string $propertyPath) : void
    {
        $oid                                   = spl_object_hash($document);
        $this->embeddedDocumentsRegistry[$oid] = $document;
        $this->parentAssociations[$oid]        = [$mapping, $parent, $propertyPath];
    }

    /**
     * Gets the parent association for a given embedded document.
     *
     *     <code>
     *     list($mapping, $parent, $propertyPath) = $this->getParentAssociation($embeddedDocument);
     *     </code>
     */
    public function getParentAssociation(object $document) : ?array
    {
        $oid = spl_object_hash($document);

        return $this->parentAssociations[$oid] ?? null;
    }

    /**
     * Get the document persister instance for the given document name
     */
    public function getDocumentPersister(string $documentName) : Persisters\DocumentPersister
    {
        if (! isset($this->persisters[$documentName])) {
            $class                           = $this->dm->getClassMetadata($documentName);
            $pb                              = $this->getPersistenceBuilder();
            $this->persisters[$documentName] = new Persisters\DocumentPersister($pb, $this->dm, $this, $this->hydratorFactory, $class);
        }

        return $this->persisters[$documentName];
    }

    /**
     * Get the collection persister instance.
     */
    public function getCollectionPersister() : CollectionPersister
    {
        if (! isset($this->collectionPersister)) {
            $pb                        = $this->getPersistenceBuilder();
            $this->collectionPersister = new Persisters\CollectionPersister($this->dm, $pb, $this);
        }

        return $this->collectionPersister;
    }

    /**
     * Set the document persister instance to use for the given document name
     *
     * @internal
     */
    public function setDocumentPersister(string $documentName, Persisters\DocumentPersister $persister) : void
    {
        $this->persisters[$documentName] = $persister;
    }

    /**
     * Commits the UnitOfWork, executing all operations that have been postponed
     * up to this point. The state of all managed documents will be synchronized with
     * the database.
     *
     * The operations are executed in the following order:
     *
     * 1) All document insertions
     * 2) All document updates
     * 3) All document deletions
     *
     * @param array $options Array of options to be used with batchInsert(), update() and remove()
     */
    public function commit(array $options = []) : void
    {
        // Raise preFlush
        if ($this->evm->hasListeners(Events::preFlush)) {
            $this->evm->dispatchEvent(Events::preFlush, new Event\PreFlushEventArgs($this->dm));
        }

        // Compute changes done since last commit.
        $this->computeChangeSets();

        if (! ($this->documentInsertions ||
            $this->documentUpserts ||
            $this->documentDeletions ||
            $this->documentUpdates ||
            $this->collectionUpdates ||
            $this->collectionDeletions ||
            $this->orphanRemovals)
        ) {
            return; // Nothing to do.
        }

        $this->commitsInProgress++;
        if ($this->commitsInProgress > 1) {
            throw MongoDBException::commitInProgress();
        }
        try {
            if ($this->orphanRemovals) {
                foreach ($this->orphanRemovals as $removal) {
                    $this->remove($removal);
                }
            }

            // Raise onFlush
            if ($this->evm->hasListeners(Events::onFlush)) {
                $this->evm->dispatchEvent(Events::onFlush, new Event\OnFlushEventArgs($this->dm));
            }

            foreach ($this->getClassesForCommitAction($this->documentUpserts) as $classAndDocuments) {
                [$class, $documents] = $classAndDocuments;
                $this->executeUpserts($class, $documents, $options);
            }

            foreach ($this->getClassesForCommitAction($this->documentInsertions) as $classAndDocuments) {
                [$class, $documents] = $classAndDocuments;
                $this->executeInserts($class, $documents, $options);
            }

            foreach ($this->getClassesForCommitAction($this->documentUpdates) as $classAndDocuments) {
                [$class, $documents] = $classAndDocuments;
                $this->executeUpdates($class, $documents, $options);
            }

            foreach ($this->getClassesForCommitAction($this->documentDeletions, true) as $classAndDocuments) {
                [$class, $documents] = $classAndDocuments;
                $this->executeDeletions($class, $documents, $options);
            }

            // Raise postFlush
            if ($this->evm->hasListeners(Events::postFlush)) {
                $this->evm->dispatchEvent(Events::postFlush, new Event\PostFlushEventArgs($this->dm));
            }

            // Clear up
            $this->documentInsertions          =
            $this->documentUpserts             =
            $this->documentUpdates             =
            $this->documentDeletions           =
            $this->documentChangeSets          =
            $this->collectionUpdates           =
            $this->collectionDeletions         =
            $this->visitedCollections          =
            $this->scheduledForSynchronization =
            $this->orphanRemovals              =
            $this->hasScheduledCollections     = [];
        } finally {
            $this->commitsInProgress--;
        }
    }

    /**
     * Groups a list of scheduled documents by their class.
     */
    private function getClassesForCommitAction(array $documents, bool $includeEmbedded = false) : array
    {
        if (empty($documents)) {
            return [];
        }

        $divided = [];
        $embeds  = [];
        foreach ($documents as $oid => $d) {
            $className = get_class($d);
            if (isset($embeds[$className])) {
                continue;
            }

            if (isset($divided[$className])) {
                $divided[$className][1][$oid] = $d;
                continue;
            }

            $class = $this->dm->getClassMetadata($className);
            if ($class->isEmbeddedDocument && ! $includeEmbedded) {
                $embeds[$className] = true;
                continue;
            }

            if ($class->isView()) {
                continue;
            }

            if (empty($divided[$class->name])) {
                $divided[$class->name] = [$class, [$oid => $d]];
            } else {
                $divided[$class->name][1][$oid] = $d;
            }
        }

        return $divided;
    }

    /**
     * Compute changesets of all documents scheduled for insertion.
     *
     * Embedded documents will not be processed.
     */
    private function computeScheduleInsertsChangeSets() : void
    {
        foreach ($this->documentInsertions as $document) {
            $class = $this->dm->getClassMetadata(get_class($document));
            if ($class->isEmbeddedDocument || $class->isView()) {
                continue;
            }

            $this->computeChangeSet($class, $document);
        }
    }

    /**
     * Compute changesets of all documents scheduled for upsert.
     *
     * Embedded documents will not be processed.
     */
    private function computeScheduleUpsertsChangeSets() : void
    {
        foreach ($this->documentUpserts as $document) {
            $class = $this->dm->getClassMetadata(get_class($document));
            if ($class->isEmbeddedDocument || $class->isView()) {
                continue;
            }

            $this->computeChangeSet($class, $document);
        }
    }

    /**
     * Gets the changeset for a document.
     *
     * @return array array('property' => array(0 => mixed|null, 1 => mixed|null))
     */
    public function getDocumentChangeSet(object $document) : array
    {
        $oid = spl_object_hash($document);

        return $this->documentChangeSets[$oid] ?? [];
    }

    /**
     * Sets the changeset for a document.
     *
     * @internal
     */
    public function setDocumentChangeSet(object $document, array $changeset) : void
    {
        $this->documentChangeSets[spl_object_hash($document)] = $changeset;
    }

    /**
     * Get a documents actual data, flattening all the objects to arrays.
     *
     * @internal
     *
     * @return array
     */
    public function getDocumentActualData(object $document) : array
    {
        $class      = $this->dm->getClassMetadata(get_class($document));
        $actualData = [];
        foreach ($class->reflFields as $name => $refProp) {
            $mapping = $class->fieldMappings[$name];
            // skip not saved fields
            if (isset($mapping['notSaved']) && $mapping['notSaved'] === true) {
                continue;
            }
            $value = $refProp->getValue($document);
            if ((isset($mapping['association']) && $mapping['type'] === 'many')
                && $value !== null && ! ($value instanceof PersistentCollectionInterface)) {
                // If $actualData[$name] is not a Collection then use an ArrayCollection.
                if (! $value instanceof Collection) {
                    $value = new ArrayCollection($value);
                }

                // Inject PersistentCollection
                $coll = $this->dm->getConfiguration()->getPersistentCollectionFactory()->create($this->dm, $mapping, $value);
                $coll->setOwner($document, $mapping);
                $coll->setDirty(! $value->isEmpty());
                $class->reflFields[$name]->setValue($document, $coll);
                $actualData[$name] = $coll;
            } else {
                $actualData[$name] = $value;
            }
        }

        return $actualData;
    }

    /**
     * Computes the changes that happened to a single document.
     *
     * Modifies/populates the following properties:
     *
     * {@link originalDocumentData}
     * If the document is NEW or MANAGED but not yet fully persisted (only has an id)
     * then it was not fetched from the database and therefore we have no original
     * document data yet. All of the current document data is stored as the original document data.
     *
     * {@link documentChangeSets}
     * The changes detected on all properties of the document are stored there.
     * A change is a tuple array where the first entry is the old value and the second
     * entry is the new value of the property. Changesets are used by persisters
     * to INSERT/UPDATE the persistent document state.
     *
     * {@link documentUpdates}
     * If the document is already fully MANAGED (has been fetched from the database before)
     * and any changes to its properties are detected, then a reference to the document is stored
     * there to mark it for an update.
     */
    public function computeChangeSet(ClassMetadata $class, object $document) : void
    {
        if (! $class->isInheritanceTypeNone()) {
            $class = $this->dm->getClassMetadata(get_class($document));
        }

        // Fire PreFlush lifecycle callbacks
        if (! empty($class->lifecycleCallbacks[Events::preFlush])) {
            $class->invokeLifecycleCallbacks(Events::preFlush, $document, [new Event\PreFlushEventArgs($this->dm)]);
        }

        $this->computeOrRecomputeChangeSet($class, $document);
    }

    /**
     * Used to do the common work of computeChangeSet and recomputeSingleDocumentChangeSet
     */
    private function computeOrRecomputeChangeSet(ClassMetadata $class, object $document, bool $recompute = false) : void
    {
        if ($class->isView()) {
            return;
        }

        $oid           = spl_object_hash($document);
        $actualData    = $this->getDocumentActualData($document);
        $isNewDocument = ! isset($this->originalDocumentData[$oid]);
        if ($isNewDocument) {
            // Document is either NEW or MANAGED but not yet fully persisted (only has an id).
            // These result in an INSERT.
            $this->originalDocumentData[$oid] = $actualData;
            $changeSet                        = [];
            foreach ($actualData as $propName => $actualValue) {
                /* At this PersistentCollection shouldn't be here, probably it
                 * was cloned and its ownership must be fixed
                 */
                if ($actualValue instanceof PersistentCollectionInterface && $actualValue->getOwner() !== $document) {
                    $actualData[$propName] = $this->fixPersistentCollectionOwnership($actualValue, $document, $class, $propName);
                    $actualValue           = $actualData[$propName];
                }
                // ignore inverse side of reference relationship
                if (isset($class->fieldMappings[$propName]['reference']) && $class->fieldMappings[$propName]['isInverseSide']) {
                    continue;
                }
                $changeSet[$propName] = [null, $actualValue];
            }
            $this->documentChangeSets[$oid] = $changeSet;
        } else {
            if ($class->isReadOnly) {
                return;
            }
            // Document is "fully" MANAGED: it was already fully persisted before
            // and we have a copy of the original data
            $originalData           = $this->originalDocumentData[$oid];
            $isChangeTrackingNotify = $class->isChangeTrackingNotify();
            if ($isChangeTrackingNotify && ! $recompute && isset($this->documentChangeSets[$oid])) {
                $changeSet = $this->documentChangeSets[$oid];
            } else {
                $changeSet = [];
            }

            $gridFSMetadataProperty = null;

            if ($class->isFile) {
                try {
                    $gridFSMetadata         = $class->getFieldMappingByDbFieldName('metadata');
                    $gridFSMetadataProperty = $gridFSMetadata['fieldName'];
                } catch (MappingException $e) {
                }
            }

            foreach ($actualData as $propName => $actualValue) {
                // skip not saved fields
                if ((isset($class->fieldMappings[$propName]['notSaved']) && $class->fieldMappings[$propName]['notSaved'] === true) ||
                    ($class->isFile && $propName !== $gridFSMetadataProperty)) {
                    continue;
                }

                $orgValue = $originalData[$propName] ?? null;

                // skip if value has not changed
                if ($orgValue === $actualValue) {
                    if (! $actualValue instanceof PersistentCollectionInterface) {
                        continue;
                    }

                    if (! $actualValue->isDirty() && ! $this->isCollectionScheduledForDeletion($actualValue)) {
                        // consider dirty collections as changed as well
                        continue;
                    }
                }

                // if relationship is a embed-one, schedule orphan removal to trigger cascade remove operations
                if (isset($class->fieldMappings[$propName]['embedded']) && $class->fieldMappings[$propName]['type'] === 'one') {
                    if ($orgValue !== null) {
                        $this->scheduleOrphanRemoval($orgValue);
                    }
                    $changeSet[$propName] = [$orgValue, $actualValue];
                    continue;
                }

                // if owning side of reference-one relationship
                if (isset($class->fieldMappings[$propName]['reference']) && $class->fieldMappings[$propName]['type'] === 'one' && $class->fieldMappings[$propName]['isOwningSide']) {
                    if ($orgValue !== null && $class->fieldMappings[$propName]['orphanRemoval']) {
                        $this->scheduleOrphanRemoval($orgValue);
                    }

                    $changeSet[$propName] = [$orgValue, $actualValue];
                    continue;
                }

                if ($isChangeTrackingNotify) {
                    continue;
                }

                // ignore inverse side of reference relationship
                if (isset($class->fieldMappings[$propName]['reference']) && $class->fieldMappings[$propName]['isInverseSide']) {
                    continue;
                }

                // Persistent collection was exchanged with the "originally"
                // created one. This can only mean it was cloned and replaced
                // on another document.
                if ($actualValue instanceof PersistentCollectionInterface && $actualValue->getOwner() !== $document) {
                    $actualValue = $this->fixPersistentCollectionOwnership($actualValue, $document, $class, $propName);
                }

                // if embed-many or reference-many relationship
                if (isset($class->fieldMappings[$propName]['type']) && $class->fieldMappings[$propName]['type'] === 'many') {
                    $changeSet[$propName] = [$orgValue, $actualValue];
                    /* If original collection was exchanged with a non-empty value
                     * and $set will be issued, there is no need to $unset it first
                     */
                    if ($actualValue && $actualValue->isDirty() && CollectionHelper::usesSet($class->fieldMappings[$propName]['strategy'])) {
                        continue;
                    }
                    if ($orgValue !== $actualValue && $orgValue instanceof PersistentCollectionInterface) {
                        $this->scheduleCollectionDeletion($orgValue);
                    }
                    continue;
                }

                // skip equivalent date values
                if (isset($class->fieldMappings[$propName]['type']) && $class->fieldMappings[$propName]['type'] === 'date') {
                    /** @var DateType $dateType */
                    $dateType      = Type::getType('date');
                    $dbOrgValue    = $dateType->convertToDatabaseValue($orgValue);
                    $dbActualValue = $dateType->convertToDatabaseValue($actualValue);

                    $orgTimestamp    = $dbOrgValue instanceof UTCDateTime ? $dbOrgValue->toDateTime()->getTimestamp() : null;
                    $actualTimestamp = $dbActualValue instanceof UTCDateTime ? $dbActualValue->toDateTime()->getTimestamp() : null;

                    if ($orgTimestamp === $actualTimestamp) {
                        continue;
                    }
                }

                // regular field
                $changeSet[$propName] = [$orgValue, $actualValue];
            }
            if ($changeSet) {
                $this->documentChangeSets[$oid] = isset($this->documentChangeSets[$oid])
                    ? $changeSet + $this->documentChangeSets[$oid]
                    : $changeSet;

                $this->originalDocumentData[$oid] = $actualData;
                $this->scheduleForUpdate($document);
            }
        }

        // Look for changes in associations of the document
        $associationMappings = array_filter(
            $class->associationMappings,
            static function ($assoc) {
                return empty($assoc['notSaved']);
            }
        );

        foreach ($associationMappings as $mapping) {
            $value = $class->reflFields[$mapping['fieldName']]->getValue($document);

            if ($value === null) {
                continue;
            }

            $this->computeAssociationChanges($document, $mapping, $value);

            if (isset($mapping['reference'])) {
                continue;
            }

            $values = $mapping['type'] === ClassMetadata::ONE ? [$value] : $value->unwrap();

            foreach ($values as $obj) {
                $oid2 = spl_object_hash($obj);

                if (isset($this->documentChangeSets[$oid2])) {
                    if (empty($this->documentChangeSets[$oid][$mapping['fieldName']])) {
                        // instance of $value is the same as it was previously otherwise there would be
                        // change set already in place
                        $this->documentChangeSets[$oid][$mapping['fieldName']] = [$value, $value];
                    }

                    if (! $isNewDocument) {
                        $this->scheduleForUpdate($document);
                    }

                    break;
                }
            }
        }
    }

    /**
     * Computes all the changes that have been done to documents and collections
     * since the last commit and stores these changes in the _documentChangeSet map
     * temporarily for access by the persisters, until the UoW commit is finished.
     */
    public function computeChangeSets() : void
    {
        $this->computeScheduleInsertsChangeSets();
        $this->computeScheduleUpsertsChangeSets();

        // Compute changes for other MANAGED documents. Change tracking policies take effect here.
        foreach ($this->identityMap as $className => $documents) {
            $class = $this->dm->getClassMetadata($className);
            if ($class->isEmbeddedDocument || $class->isView()) {
                /* we do not want to compute changes to embedded documents up front
                 * in case embedded document was replaced and its changeset
                 * would corrupt data. Embedded documents' change set will
                 * be calculated by reachability from owning document.
                 */
                continue;
            }

            // If change tracking is explicit or happens through notification, then only compute
            // changes on document of that type that are explicitly marked for synchronization.
            switch (true) {
                case $class->isChangeTrackingDeferredImplicit():
                    $documentsToProcess = $documents;
                    break;

                case isset($this->scheduledForSynchronization[$className]):
                    $documentsToProcess = $this->scheduledForSynchronization[$className];
                    break;

                default:
                    $documentsToProcess = [];
            }

            foreach ($documentsToProcess as $document) {
                // Ignore uninitialized proxy objects
                if ($document instanceof GhostObjectInterface && ! $document->isProxyInitialized()) {
                    continue;
                }
                // Only MANAGED documents that are NOT SCHEDULED FOR INSERTION, UPSERT OR DELETION are processed here.
                $oid = spl_object_hash($document);
                if (isset($this->documentInsertions[$oid])
                    || isset($this->documentUpserts[$oid])
                    || isset($this->documentDeletions[$oid])
                    || ! isset($this->documentStates[$oid])
                ) {
                    continue;
                }

                $this->computeChangeSet($class, $document);
            }
        }
    }

    /**
     * Computes the changes of an association.
     *
     * @param mixed $value The value of the association.
     *
     * @throws InvalidArgumentException
     */
    private function computeAssociationChanges(object $parentDocument, array $assoc, $value) : void
    {
        $isNewParentDocument   = isset($this->documentInsertions[spl_object_hash($parentDocument)]);
        $class                 = $this->dm->getClassMetadata(get_class($parentDocument));
        $topOrExistingDocument = ( ! $isNewParentDocument || ! $class->isEmbeddedDocument);

        if ($value instanceof GhostObjectInterface && ! $value->isProxyInitialized()) {
            return;
        }

        if ($value instanceof PersistentCollectionInterface && $value->isDirty() && $value->getOwner() !== null && ($assoc['isOwningSide'] || isset($assoc['embedded']))) {
            if ($topOrExistingDocument || CollectionHelper::usesSet($assoc['strategy'])) {
                $this->scheduleCollectionUpdate($value);
            }

            $topmostOwner                                               = $this->getOwningDocument($value->getOwner());
            $this->visitedCollections[spl_object_hash($topmostOwner)][] = $value;
            if (! empty($assoc['orphanRemoval']) || isset($assoc['embedded'])) {
                $value->initialize();
                foreach ($value->getDeletedDocuments() as $orphan) {
                    $this->scheduleOrphanRemoval($orphan);
                }
            }
        }

        // Look through the documents, and in any of their associations,
        // for transient (new) documents, recursively. ("Persistence by reachability")
        // Unwrap. Uninitialized collections will simply be empty.
        $unwrappedValue = $assoc['type'] === ClassMetadata::ONE ? [$value] : $value->unwrap();

        $count = 0;
        foreach ($unwrappedValue as $key => $entry) {
            if (! is_object($entry)) {
                throw new InvalidArgumentException(
                    sprintf('Expected object, found "%s" in %s::%s', $entry, get_class($parentDocument), $assoc['name'])
                );
            }

            $targetClass = $this->dm->getClassMetadata(get_class($entry));

            $state = $this->getDocumentState($entry, self::STATE_NEW);

            // Handle "set" strategy for multi-level hierarchy
            $pathKey = ! isset($assoc['strategy']) || CollectionHelper::isList($assoc['strategy']) ? $count : $key;
            $path    = $assoc['type'] === 'many' ? $assoc['name'] . '.' . $pathKey : $assoc['name'];

            $count++;

            switch ($state) {
                case self::STATE_NEW:
                    if (! $assoc['isCascadePersist']) {
                        throw new InvalidArgumentException('A new document was found through a relationship that was not'
                            . ' configured to cascade persist operations: ' . $this->objToStr($entry) . '.'
                            . ' Explicitly persist the new document or configure cascading persist operations'
                            . ' on the relationship.');
                    }

                    $this->persistNew($targetClass, $entry);
                    $this->setParentAssociation($entry, $assoc, $parentDocument, $path);
                    $this->computeChangeSet($targetClass, $entry);
                    break;

                case self::STATE_MANAGED:
                    if ($targetClass->isEmbeddedDocument) {
                        [, $knownParent ] = $this->getParentAssociation($entry);
                        if ($knownParent && $knownParent !== $parentDocument) {
                            $entry = clone $entry;
                            if ($assoc['type'] === ClassMetadata::ONE) {
                                $class->setFieldValue($parentDocument, $assoc['fieldName'], $entry);
                                $this->setOriginalDocumentProperty(spl_object_hash($parentDocument), $assoc['fieldName'], $entry);
                                $poid = spl_object_hash($parentDocument);
                                if (isset($this->documentChangeSets[$poid][$assoc['fieldName']])) {
                                    $this->documentChangeSets[$poid][$assoc['fieldName']][1] = $entry;
                                }
                            } else {
                                // must use unwrapped value to not trigger orphan removal
                                $unwrappedValue[$key] = $entry;
                            }
                            $this->persistNew($targetClass, $entry);
                        }
                        $this->setParentAssociation($entry, $assoc, $parentDocument, $path);
                        $this->computeChangeSet($targetClass, $entry);
                    }
                    break;

                case self::STATE_REMOVED:
                    // Consume the $value as array (it's either an array or an ArrayAccess)
                    // and remove the element from Collection.
                    if ($assoc['type'] === ClassMetadata::MANY) {
                        unset($value[$key]);
                    }
                    break;

                case self::STATE_DETACHED:
                    // Can actually not happen right now as we assume STATE_NEW,
                    // so the exception will be raised from the DBAL layer (constraint violation).
                    throw new InvalidArgumentException('A detached document was found through a '
                        . 'relationship during cascading a persist operation.');

                default:
                    // MANAGED associated documents are already taken into account
                    // during changeset calculation anyway, since they are in the identity map.
            }
        }
    }

    /**
     * Computes the changeset of an individual document, independently of the
     * computeChangeSets() routine that is used at the beginning of a UnitOfWork#commit().
     *
     * The passed document must be a managed document. If the document already has a change set
     * because this method is invoked during a commit cycle then the change sets are added.
     * whereby changes detected in this method prevail.
     *
     * @throws InvalidArgumentException If the passed document is not MANAGED.
     */
    public function recomputeSingleDocumentChangeSet(ClassMetadata $class, object $document) : void
    {
        // Ignore uninitialized proxy objects
        if ($document instanceof GhostObjectInterface && ! $document->isProxyInitialized()) {
            return;
        }

        $oid = spl_object_hash($document);

        if (! isset($this->documentStates[$oid]) || $this->documentStates[$oid] !== self::STATE_MANAGED) {
            throw new InvalidArgumentException('Document must be managed.');
        }

        if (! $class->isInheritanceTypeNone()) {
            $class = $this->dm->getClassMetadata(get_class($document));
        }

        $this->computeOrRecomputeChangeSet($class, $document, true);
    }

    /**
     * @throws InvalidArgumentException If there is something wrong with document's identifier.
     */
    private function persistNew(ClassMetadata $class, object $document) : void
    {
        $this->lifecycleEventManager->prePersist($class, $document);
        $oid    = spl_object_hash($document);
        $upsert = false;
        if ($class->identifier) {
            $idValue = $class->getIdentifierValue($document);
            $upsert  = ! $class->isEmbeddedDocument && $idValue !== null;

            if ($class->generatorType === ClassMetadata::GENERATOR_TYPE_NONE && $idValue === null) {
                throw new InvalidArgumentException(sprintf(
                    '%s uses NONE identifier generation strategy but no identifier was provided when persisting.',
                    get_class($document)
                ));
            }

            if ($class->generatorType === ClassMetadata::GENERATOR_TYPE_AUTO && $idValue !== null && ! preg_match('#^[0-9a-f]{24}$#', (string) $idValue)) {
                throw new InvalidArgumentException(sprintf(
                    '%s uses AUTO identifier generation strategy but provided identifier is not a valid ObjectId.',
                    get_class($document)
                ));
            }

            if ($class->generatorType !== ClassMetadata::GENERATOR_TYPE_NONE && $idValue === null && $class->idGenerator !== null) {
                $idValue = $class->idGenerator->generate($this->dm, $document);
                $idValue = $class->getPHPIdentifierValue($class->getDatabaseIdentifierValue($idValue));
                $class->setIdentifierValue($document, $idValue);
            }

            $this->documentIdentifiers[$oid] = $idValue;
        } else {
            // this is for embedded documents without identifiers
            $this->documentIdentifiers[$oid] = $oid;
        }

        $this->documentStates[$oid] = self::STATE_MANAGED;

        if ($upsert) {
            $this->scheduleForUpsert($class, $document);
        } else {
            $this->scheduleForInsert($class, $document);
        }
    }

    /**
     * Executes all document insertions for documents of the specified type.
     */
    private function executeInserts(ClassMetadata $class, array $documents, array $options = []) : void
    {
        $persister = $this->getDocumentPersister($class->name);

        foreach ($documents as $oid => $document) {
            $persister->addInsert($document);
            unset($this->documentInsertions[$oid]);
        }

        $persister->executeInserts($options);

        foreach ($documents as $document) {
            $this->lifecycleEventManager->postPersist($class, $document);
        }
    }

    /**
     * Executes all document upserts for documents of the specified type.
     */
    private function executeUpserts(ClassMetadata $class, array $documents, array $options = []) : void
    {
        $persister = $this->getDocumentPersister($class->name);

        foreach ($documents as $oid => $document) {
            $persister->addUpsert($document);
            unset($this->documentUpserts[$oid]);
        }

        $persister->executeUpserts($options);

        foreach ($documents as $document) {
            $this->lifecycleEventManager->postPersist($class, $document);
        }
    }

    /**
     * Executes all document updates for documents of the specified type.
     */
    private function executeUpdates(ClassMetadata $class, array $documents, array $options = []) : void
    {
        if ($class->isReadOnly) {
            return;
        }

        $className = $class->name;
        $persister = $this->getDocumentPersister($className);

        foreach ($documents as $oid => $document) {
            $this->lifecycleEventManager->preUpdate($class, $document);

            if (! empty($this->documentChangeSets[$oid]) || $this->hasScheduledCollections($document)) {
                $persister->update($document, $options);
            }

            unset($this->documentUpdates[$oid]);

            $this->lifecycleEventManager->postUpdate($class, $document);
        }
    }

    /**
     * Executes all document deletions for documents of the specified type.
     */
    private function executeDeletions(ClassMetadata $class, array $documents, array $options = []) : void
    {
        $persister = $this->getDocumentPersister($class->name);

        foreach ($documents as $oid => $document) {
            if (! $class->isEmbeddedDocument) {
                $persister->delete($document, $options);
            }
            unset(
                $this->documentDeletions[$oid],
                $this->documentIdentifiers[$oid],
                $this->originalDocumentData[$oid]
            );

            // Clear snapshot information for any referenced PersistentCollection
            // http://www.doctrine-project.org/jira/browse/MODM-95
            foreach ($class->associationMappings as $fieldMapping) {
                if (! isset($fieldMapping['type']) || $fieldMapping['type'] !== ClassMetadata::MANY) {
                    continue;
                }

                $value = $class->reflFields[$fieldMapping['fieldName']]->getValue($document);
                if (! ($value instanceof PersistentCollectionInterface)) {
                    continue;
                }

                $value->clearSnapshot();
            }

            // Document with this $oid after deletion treated as NEW, even if the $oid
            // is obtained by a new document because the old one went out of scope.
            $this->documentStates[$oid] = self::STATE_NEW;

            $this->lifecycleEventManager->postRemove($class, $document);
        }
    }

    /**
     * Schedules a document for insertion into the database.
     * If the document already has an identifier, it will be added to the
     * identity map.
     *
     * @internal
     *
     * @throws InvalidArgumentException
     */
    public function scheduleForInsert(ClassMetadata $class, object $document) : void
    {
        $oid = spl_object_hash($document);

        if (isset($this->documentUpdates[$oid])) {
            throw new InvalidArgumentException('Dirty document can not be scheduled for insertion.');
        }
        if (isset($this->documentDeletions[$oid])) {
            throw new InvalidArgumentException('Removed document can not be scheduled for insertion.');
        }
        if (isset($this->documentInsertions[$oid])) {
            throw new InvalidArgumentException('Document can not be scheduled for insertion twice.');
        }

        $this->documentInsertions[$oid] = $document;

        if (! isset($this->documentIdentifiers[$oid])) {
            return;
        }

        $this->addToIdentityMap($document);
    }

    /**
     * Schedules a document for upsert into the database and adds it to the
     * identity map
     *
     * @internal
     *
     * @throws InvalidArgumentException
     */
    public function scheduleForUpsert(ClassMetadata $class, object $document) : void
    {
        $oid = spl_object_hash($document);

        if ($class->isEmbeddedDocument) {
            throw new InvalidArgumentException('Embedded document can not be scheduled for upsert.');
        }
        if (isset($this->documentUpdates[$oid])) {
            throw new InvalidArgumentException('Dirty document can not be scheduled for upsert.');
        }
        if (isset($this->documentDeletions[$oid])) {
            throw new InvalidArgumentException('Removed document can not be scheduled for upsert.');
        }
        if (isset($this->documentUpserts[$oid])) {
            throw new InvalidArgumentException('Document can not be scheduled for upsert twice.');
        }

        $this->documentUpserts[$oid]     = $document;
        $this->documentIdentifiers[$oid] = $class->getIdentifierValue($document);
        $this->addToIdentityMap($document);
    }

    /**
     * Checks whether a document is scheduled for insertion.
     */
    public function isScheduledForInsert(object $document) : bool
    {
        return isset($this->documentInsertions[spl_object_hash($document)]);
    }

    /**
     * Checks whether a document is scheduled for upsert.
     */
    public function isScheduledForUpsert(object $document) : bool
    {
        return isset($this->documentUpserts[spl_object_hash($document)]);
    }

    /**
     * Schedules a document for being updated.
     *
     * @internal
     *
     * @throws InvalidArgumentException
     */
    public function scheduleForUpdate(object $document) : void
    {
        $oid = spl_object_hash($document);
        if (! isset($this->documentIdentifiers[$oid])) {
            throw new InvalidArgumentException('Document has no identity.');
        }

        if (isset($this->documentDeletions[$oid])) {
            throw new InvalidArgumentException('Document is removed.');
        }

        if (isset($this->documentUpdates[$oid])
            || isset($this->documentInsertions[$oid])
            || isset($this->documentUpserts[$oid])) {
            return;
        }

        $this->documentUpdates[$oid] = $document;
    }

    /**
     * Checks whether a document is registered as dirty in the unit of work.
     * Note: Is not very useful currently as dirty documents are only registered
     * at commit time.
     */
    public function isScheduledForUpdate(object $document) : bool
    {
        return isset($this->documentUpdates[spl_object_hash($document)]);
    }

    /**
     * Checks whether a document is registered to be checked in the unit of work.
     */
    public function isScheduledForSynchronization(object $document) : bool
    {
        $class = $this->dm->getClassMetadata(get_class($document));

        return isset($this->scheduledForSynchronization[$class->name][spl_object_hash($document)]);
    }

    /**
     * Schedules a document for deletion.
     *
     * @internal
     */
    public function scheduleForDelete(object $document, bool $isView = false) : void
    {
        $oid = spl_object_hash($document);

        if (isset($this->documentInsertions[$oid])) {
            if ($this->isInIdentityMap($document)) {
                $this->removeFromIdentityMap($document);
            }
            unset($this->documentInsertions[$oid]);

            return; // document has not been persisted yet, so nothing more to do.
        }

        if (! $this->isInIdentityMap($document)) {
            return; // ignore
        }

        $this->removeFromIdentityMap($document);
        $this->documentStates[$oid] = self::STATE_REMOVED;

        if (isset($this->documentUpdates[$oid])) {
            unset($this->documentUpdates[$oid]);
        }
        if (isset($this->documentDeletions[$oid])) {
            return;
        }

        if ($isView) {
            return;
        }

        $this->documentDeletions[$oid] = $document;
    }

    /**
     * Checks whether a document is registered as removed/deleted with the unit
     * of work.
     */
    public function isScheduledForDelete(object $document) : bool
    {
        return isset($this->documentDeletions[spl_object_hash($document)]);
    }

    /**
     * Checks whether a document is scheduled for insertion, update or deletion.
     *
     * @internal
     */
    public function isDocument…