Limitations and Known Issues

Join-Columns with non-primary keys

It is not possible to use join columns pointing to non-primary keys. Doctrine will think these are the primary keys and create lazy-loading proxies with the data, which can lead to unexpected results. Doctrine can for performance reasons not validate the correctness of this settings at runtime but only through the Validate Schema command.

Mapping Arrays to a Join Table

Related to the previous limitation with "Foreign Keys as Identifier" you might be interested in mapping the same table structure as given above to an array. However this is not yet possible either. See the following example:

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CREATE TABLE product (
    id INTEGER,
    name VARCHAR,
    PRIMARY KEY(id)
);

CREATE TABLE product_attributes (
    product_id INTEGER,
    attribute_name VARCHAR,
    attribute_value VARCHAR,
    PRIMARY KEY (product_id, attribute_name)
);
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This schema should be mapped to a Product Entity as follows:

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class Product
{
    private $id;
    private $name;
    private $attributes = array();
}
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Where the attribute_name column contains the key and attribute_value contains the value of each array element in $attributes.

The feature request for persistence of primitive value arrays is described in the DDC-298 ticket.

Cascade Merge with Bi-directional Associations

There are two bugs now that concern the use of cascade merge in combination with bi-directional associations. Make sure to study the behavior of cascade merge if you are using it:

• DDC-875 Merge can sometimes add the same entity twice into a collection
• DDC-763 Cascade merge on associated entities can insert too many rows through "Persistence by Reachability"

Custom Persisters

A Persister in Doctrine is an object that is responsible for the hydration and write operations of an entity against the database. Currently there is no way to overwrite the persister implementation for a given entity, however there are several use-cases that can benefit from custom persister implementations:

• Add Upsert Support
• Evaluate possible ways in which stored-procedures can be used

Persist Keys of Collections

PHP Arrays are ordered hash-maps and so should be the Doctrine\Common\Collections\Collection interface. We plan to evaluate a feature that optionally persists and hydrates the keys of a Collection instance.

Ticket DDC-213

Mapping many tables to one entity

It is not possible to map several equally looking tables onto one entity. For example if you have a production and an archive table of a certain business concept then you cannot have both tables map to the same entity.

Behaviors

Doctrine ORM will never include a behavior system like Doctrine 1 in the core library. We don't think behaviors add more value than they cost pain and debugging hell. Please see the many different blog posts we have written on this topics:

• Doctrine2 "Behaviors" in a Nutshell
• A re-usable Versionable behavior for Doctrine2
• Write your own ORM on top of Doctrine2
• Doctrine ORM Behavioral Extensions

Doctrine ORM has enough hooks and extension points so that you can add whatever you want on top of it. None of this will ever become core functionality of Doctrine2 however, you will have to rely on third party extensions for magical behaviors.

Nested Set

NestedSet was offered as a behavior in Doctrine 1 and will not be included in the core of Doctrine ORM. However there are already two extensions out there that offer support for Nested Set with ORM:

• Doctrine2 Hierarchical-Structural Behavior
• Doctrine2 NestedSet

Using Traits in Entity Classes

The use of traits in entity or mapped superclasses, at least when they include mapping configuration or mapped fields, is currently not endorsed by the Doctrine project. The reasons for this are as follows.

Traits were added in PHP 5.4 more than 10 years ago, but at the same time more than two years after the initial Doctrine 2 release and the time where core components were designed.

In fact, this documentation mentions traits only in the context of overriding field association mappings in subclasses. Coverage of traits in test cases is practically nonexistent.

Thus, you should at least be aware that when using traits in your entity and mapped superclasses, you will be in uncharted terrain.

From a more technical point of view, traits basically work at the language level as if the code contained in them had been copied into the class where the trait is used, and even private fields are accessible by the using class. In addition to that, some precedence and conflict resolution rules apply.

When it comes to loading mapping configuration, the annotation and attribute drivers rely on PHP reflection to inspect class properties including their docblocks. As long as the results are consistent with what a solution without traits would have produced, this is probably fine.

However, to mention known limitations, it is currently not possible to use "class" level annotations or attributes on traits, and attempts to improve parser support for traits as here or there have been abandoned due to complexity.

XML mapping configuration probably needs to completely re-configure or otherwise copy-and-paste configuration for fields used from traits.

Identifier Quoting and Legacy Databases

For compatibility reasons between all the supported vendors and edge case problems Doctrine ORM does NOT do automatic identifier quoting. This can lead to problems when trying to get legacy-databases to work with Doctrine ORM.

• You can quote column-names as described in the Basic-Mapping section.
• You cannot quote join column names.
• You cannot use non [a-zA-Z0-9_]+ characters, they will break several SQL statements.

Having problems with these kind of column names? Many databases support all CRUD operations on views that semantically map to certain tables. You can create views for all your problematic tables and column names to avoid the legacy quoting nightmare.

Microsoft SQL Server and Doctrine "datetime"

Doctrine assumes that you use DateTime2 data-types. If your legacy database contains DateTime datatypes then you have to add your own data-type (see Basic Mapping for an example).

MySQL with MyISAM tables

Doctrine cannot provide atomic operations when calling EntityManager#flush() if one of the tables involved uses the storage engine MyISAM. You must use InnoDB or other storage engines that support transactions if you need integrity.