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Add note box on cascade operations being performed in memory and reference to foreign key /database-level onDelete option for deleting associtions

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Benjamin Eberlei 2011-04-06 23:36:50 +02:00
parent a0b41feb72
commit f76728818b

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@ -413,8 +413,8 @@ Transitive persistence / Cascade Operations
------------------------------------------- -------------------------------------------
Persisting, removing, detaching and merging individual entities can Persisting, removing, detaching and merging individual entities can
become pretty cumbersome, especially when a large object graph become pretty cumbersome, especially when a highly interveawed object graph
with collections is involved. Therefore Doctrine 2 provides a is involved. Therefore Doctrine 2 provides a
mechanism for transitive persistence through cascading of these mechanism for transitive persistence through cascading of these
operations. Each association to another entity or a collection of operations. Each association to another entity or a collection of
entities can be configured to automatically cascade certain entities can be configured to automatically cascade certain
@ -431,6 +431,21 @@ The following cascade options exist:
- all : Cascades persist, remove, merge and detach operations to - all : Cascades persist, remove, merge and detach operations to
associated entities. associated entities.
.. note::
Cascade operations are performed in memory. That means collections and related entities
are fetched into memory, even if they are still marked as lazy when
the cascade operation is about to be performed. However this approach allows
entity lifecycle events to be performed for each of these operations.
However, pulling objects graph into memory on cascade can cause considerable performance
overhead, especially when cascading collections are large. Makes sure
to weigh the benefits and downsides of each cascade operation that you define.
To rely on the database level cascade operations for the delete operation instead, you can
configure each join column with the **onDelete** option. See the respective
mapping driver chapters for more information.
The following example is an extension to the User-Comment example The following example is an extension to the User-Comment example
of this chapter. Suppose in our application a user is created of this chapter. Suppose in our application a user is created
whenever he writes his first comment. In this case we would use the whenever he writes his first comment. In this case we would use the