Re: CoreData modeling a mutable attribute set for an entity
Re: CoreData modeling a mutable attribute set for an entity
- Subject: Re: CoreData modeling a mutable attribute set for an entity
- From: Jesse Grosjean <email@hidden>
- Date: Wed, 11 Jan 2006 14:01:44 -0500
I'm picking up this older thread with a new related question:
"CoreData modeling a mutable attribute set for an entity"
http://www.cocoabuilder.com/archive/message/cocoa/2006/1/3/153637
I'm looking for the best way to do AND queries on attributes that are
added to my Entry objects. My data model is generic in that it allows
users to add their own attributes to my entry objects. I'm now using
this basic design:
EntryClass
extendedAttributes (to many relationship)
ExtendedAttributeClass
entry (to one relationship)
name (string)
type (int)
stringValue (string)
numberValue (int/float/double/whatever)
dateValue (date)
dataValue (binary)
Each entry has a relationship to a collection of attributes. These
attributes have a key field and then a number of value fields, most
of which will be empty for any given attributes. So a typical
instance of this model would be:
MyEntry1
attribute key="name" stringValue="John"
attribute key="age" numberValue=29
MyEntry2
attribute key="name" stringValue="Jane"
attribute key="age" numberValue=29
... which represents two entries, each representing a different
person. To query this model I run my query on the
ExtendedAttributeClass and then iterate over the results following
the 'entry' relationship back to find the corresponding EntryClass
object. This all seems to be working, but I've run into one last
problem. What's the best way to run an AND query on this model? For
instance in the above example what query do I run if I want to find
the EntryClass who's name="John" AND age=29?
The only solution that I can come up with is to run a separate query
for each subpredicate of the AND clause and then do an intersection
of all the result sets. Ideally I would like to avoid the multiple
queries if possible, is there a better way to run AND queries on this
model that I'm not thinking about?
Thanks,
Jesse
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