UnitOfWork through Doctrine Events. Slides from OroMeetup #7. Kharkiv

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Doctrine internals
UnitOfWork

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About me
https://www.facebook.com/yatsenco
https://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 trip
It 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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Doctrine Internals. UnitOfWork
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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Doctrine Internals. UnitOfWork
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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Doctrine Internals. UnitOfWork
2) Update
Object changes outside Doctrine.
● Direct changes
● Forms (PropertyAccessor)
● etc.

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Doctrine Internals. UnitOfWork
3) Flush
Sync changes with the Database

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Doctrine Internals. UnitOfWork
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
Fetch
Repo-> find|refresh|getReference|etc.
● (optional) sync data with DB
● Events::loadClassMetadata
○ If ! Events:onClassMetadataNotFound
● hydrate
● Events:postLoad

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

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Doctrine Internals. UnitOfWork
Remove
● Events::preRemove
● UOW->scheduleForDelete($entity)

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Doctrine Internals. UnitOfWork
Flush
● UOW->commit(null|object|array $entity)

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Doctrine Internals. UnitOfWork
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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Doctrine Internals. UnitOfWork
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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Doctrine Internals. UnitOfWork
Flush (5)
● Deletions
○ Persister->delete($entity)
○ Events::postRemove
■ nothing to update here

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

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Doctrine Internals. UnitOfWork
How to speed-up doctrine
● Cache
○ Metadata
○ Query
○ result

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Doctrine Internals. UnitOfWork
How to speed-up doctrine
● Control lazy-loading
○ Never eager load
○ Write select queries with joins to needed

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Doctrine Internals. UnitOfWork
How to speed-up doctrine
● Fetch less
○ getReference
○ {partial}

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Doctrine Internals. UnitOfWork
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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Doctrine Internals. UnitOfWork
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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Doctrine Internals. UnitOfWork
How to speed-up doctrine
● Optimize queries

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Doctrine Internals. UnitOfWork
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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