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Doctrine internalsUnitOfWork

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About me

https://www.facebook.com/yatsencohttps://github.com/anyt

about me…

Andrey Yatsenco

● PHP Developer at Oro Inc.● 3 years with Symfony ● 6 years with PHP

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Doctrine Internals. UnitOfWork

Introduction● Doctrine is the bottleneck for many apps● You know how UnitOfWork is working, you

know how doctrine works

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Doctrine Internals. UnitOfWork

UnitOfWork track objects changes and commit them transactionally to the Database.Now you don’t manage object loading from the DataBase. UOW do.

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Doctrine Internals. UnitOfWork

UOW use IdentityMap to track objects changes and to avoid server round tripIt simple two level array storage● First level keys are ClassNames● Second level keys are object IDs.

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Doctrine Internals. UnitOfWork

Doctrine EntityManager is like all-in-one decorator on● Repository● UnitOfWork● MetadataFactory● ProxyFactory● etc.

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Doctrine Internals. UnitOfWork

EntityManager -> EntityRepository● find● findOneBy● findAll● customFindQueryWithHidration● etc.

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Doctrine Internals. UnitOfWork

EntityManager->UnitOfWork● persist● refresh● remove● flush ● etc.

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EntityManager->UnitOfWork● persist ● refresh ● remove● commit● etc.

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Doctrine Internals. UnitOfWork

Doctrine flow ● 1) Fetch entities from the database or

create new and persist ‘em (Repo|UOW)● 2) Update some of entities directly or using

wrapper like Form (uses PropertyAccess)● Remove some, if needed (Forms etc.)● 3) EM->flush() changes (UOW)

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1) Fetching entities from the DB● One entity:

○ find○ findOneBy

● Several entities:○ Lazy/Eager loading○ Find partial

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Doctrine Internals. UnitOfWork

1) Persist● Can be omitted if you fetched entities from

doctrine● Required only for newly created entities

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2) Update Object changes outside Doctrine.● Direct changes● Forms (PropertyAccessor)● etc.

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Doctrine Internals. UnitOfWork

3) FlushSync changes with the Database

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3) Flush Flow● Open DB transaction● Complute change-sets for update● Iterate over scheduled inserts, updates,

deletes● Delegate to entity persister SQL generation

and execution● Clear UOW on success● Close DB transaction

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Doctrine Internals. UnitOfWork

UnitOfWork through Doctrine Events● fetch● persist● remove● flush

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Doctrine Internals. UnitOfWork

FetchRepo-> find|refresh|getReference|etc.● (optional) sync data with DB● Events::loadClassMetadata

○ If ! Events:onClassMetadataNotFound● hydrate● Events:postLoad

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Persist● Events:prePersist● Entity ID isn’t exist at this time in most cases● UOW->scheduleForInsert($entity)

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Remove● Events::preRemove● UOW->scheduleForDelete($entity)

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Flush● UOW->commit(null|object|array $entity)

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Flush (1)● Events::preFlush

○ $em->flush() can be called safely● compute insert|update|delete changesets● If !changes

○ Events::onFlush○ Events::postFlush○ return

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Doctrine Internals. UnitOfWork

Flush (2)● Events::onFlush

○ UOW->getScheduledEntityInsertions()○ UOW->getScheduledEntityUpdates()○ UOW->getScheduledEntityDeletions()○ $em->persist() && UOW-

>computeChangeSet()● connection->beginTransaction

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Doctrine Internals. UnitOfWork

Flush (3)● Inserts

○ Persister->insert($entity)○ Events::postPersist

■ entity can’t be updated directly anymore■ UOW->scheduleExtraUpdate($entity, array $changeset)

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Flush (4)● Updates

○ Events::preUpdate■ Entity can’t be updated directly, update changeset using

PreUpdateEventArgs■ Relations changes not tracked too

○ UOW->recomputeSingleEntityChangeSet($class, $entity)○ Persister->update($entity)○ Events::postUpdate

■ Entity can’t be updated directly anymore■ UOW->scheduleExtraUpdate($entity, array $changeset)

● UOW->executeExtraUpdates()

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Flush (5)● Deletions

○ Persister->delete($entity)○ Events::postRemove

■ nothing to update here

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Flush (6)● connection->commit()● Events::postFlush

○ Never call $em->flush() here● UOW->clear();

○ Events::onClear● in case of errors

○ connection->rollback()That’s it.

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Let’s talk a little bit about performance and how to speed-up doctrine

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How to speed-up doctrine● Cache

○ Metadata○ Query○ result

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How to speed-up doctrine● Control lazy-loading

○ Never eager load○ Write select queries with joins to needed

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How to speed-up doctrine● Fetch less

○ getReference○ {partial}

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How to speed-up doctrine● Hydrate less

○ arrays instead of objects when you don’t need them or performance is important

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How to speed-up doctrine● Make flush cheaper

○ Mark entities as readOnly○ Chang tracking policy to

DEFERRED_EXPLICIT or NOTIFY○ Provide flush arguments (applies

objects and arrays)

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How to speed-up doctrine● Optimize queries

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Links:docs

● http://www.doctrine-project.org/api/orm/2.0/class-Doctrine.ORM.UnitOfWork.html● http://doctrine-orm.readthedocs.io/projects/doctrine-orm/

Patterns● http://martinfowler.com/eaaCatalog/unitOfWork.html● http://martinfowler.com/eaaCatalog/identityMap.html

Sergey Zhuravel presentation about Doctrine Events● http://www.slideshare.net/sergeyz/oro-meetups-doctrine-events?qid=7d9177e9-c41c-4642-

bdba-e1fa3060bb17&v=&b=&from_search=1

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