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Advanced Faulting

This section discusses the advanced faulting techniques available in Enterprise Objects.

In this section:

Deferred Faulting
Batch Faulting

Deferred Faulting

As described in “Faulting and Relationship Resolution,” Enterprise Objects uses faults to improve application performance. Fault creation is much faster than enterprise object creation and faults consume fewer resources than whole enterprise object instances. However, fault instantiation still takes time. To improve performance even further, Enterprise Objects uses deferred faults.

In an enterprise object class that can use deferred faulting, the object’s relationships are initialized as deferred faults. For a particular relationship, a single deferred fault is shared between all instances of an enterprise object class. This sharing can significantly reduce the number of faults that need to be created and usually reduces the overhead of fault creation during a fetch.

For example, consider a Listing entity that has an agent relationship. Assuming the worst case in which each Listing enterprise object has a different Agent enterprise object, without deferred faulting, a fetch of twenty Listing objects results in the creation of twenty faults for the agent relationship—a fault for each Listing. With deferred faulting, only one fault is created—a deferred fault that is shared by all the Listing objects.

If you use EOGenericRecord subclasses for your custom enterprise object classes as described in “Which Enterprise Object Class?,” those classes automatically use deferred faulting. If your custom enterprise object classes instead inherit from EOCustomObject and you want to enable deferred faulting in them, override the method usesDeferredFaultCreation to return true in those classes, as Listing 3-2 does. In those classes, you must also invoke willReadRelationship before accessing a relationship that might be a deferred fault.

Batch Faulting

Another advanced faulting feature is batch faulting. When a fault is fired, its data is fetched from the database. However, firing one fault has no effect on other faults—firing one fault just fetches the object or objects for the one fault. By batching fault firings together, you can more efficiently use the round trip to the database that is necessary when a single fault is fired.

For example, given an array of Employee enterprise objects, you can fetch all of the objects that are the destination of their department relationship with one round trip to the server. Without batch faulting, a round trip to the database is made to resolve each Employee’s department relationship.

There are a number of ways to implement batch faulting. You can configure batch faulting in three contexts: on entities, on relationships, and on relationships under certain circumstances.

You configure batch faulting for an entity in EOModeler in an entity’s advanced inspector, as shown in Figure 6-5. The integer you specify in the Batch Faulting Size field specifies the number of faults to fire the first time a fault is fired for any relationship in that entity. You can set this size programmatically using the method in EOEntity called setMaxNumberOfInstancesToBatchFetch.

You can also specify a batch faulting size for a particular relationship. The easiest and most common way to do this is in EOModeler using the advanced relationship inspector, which is shown in Figure 6-6. The batch size specifies the number of faults to fire when the first fault in the relationship is fired.

Finally, you can take more precise control of batch faulting by explicitly batching together faults for particular objects. When you specify the batch size in EOModeler for all of an entity’s relationships or for particular relationships, you don’t actually control which faults are fired. The method batchFetchRelationship in EODatabaseContext allows you to batch fetch all of the faults in a particular relationship. The method databaseContextShouldFetchArrayFault in EODatabaseContext.Delegate allows you to turn batch faulting on and off arbitrarily. See the API reference for EODatabaseContext and EODatabaseContext.Delegate for more details.

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