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Re: Saving Images with Core Data (i.e., JPEG, TIFF, etc.)


On Apr 29, 2005, at 2:16 PM, mmalcolm crawford wrote:


On Apr 29, 2005, at 1:41 PM, Jim Correia wrote:


On Apr 29, 2005, at 2:37 PM, mmalcolm crawford wrote:

For example, if a Person entity should have a 'photo' attribute, then create a Photo entity with just a single attribute -- the data -- and if you care a relationship back to the Person (typically modeling relationships in both directions is a Good Thing). Then create a relationship from the Person to the Photo entity. This will mean that photo data is only loaded from the persistent store if you actually use it.

Watch out for many-many relationships. They can be a true performance killer.

Is this true in general (or at least for SQLite stores)? Relationships are loaded on demand, but attributes are loaded when the object is?

Faulting only applies to relationships (so in your example comments will be loaded along with the other attributes on fetch), and is only really relevant if you use a SQLite store since it can fetch data on an as-needed basis. The other stores -- XML and binary -- both load the whole persistent store into memory when they're accessed.

What about fetched properties? The docs imply a lazy fetch, but I have not had a chance to test.

On the other hand, I am not sure I grok when I would use a fetched property, as opposed to a stored fetch request. Is there an implicit "must be in a relatioship with the entity that the fetched property is a part of" condition on a fetched property, or some such?

Scott

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References: 
 >Saving Images with Core Data (i.e., JPEG, TIFF, etc.) (From: Marc Blatt <email@hidden>)
 >Re: Saving Images with Core Data (i.e., JPEG, TIFF, etc.) (From: mmalcolm crawford <email@hidden>)
 >Re: Saving Images with Core Data (i.e., JPEG, TIFF, etc.) (From: Jim Correia <email@hidden>)
 >Re: Saving Images with Core Data (i.e., JPEG, TIFF, etc.) (From: mmalcolm crawford <email@hidden>)



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