Is a query on type User more expensive than querying on type Key?
In storing references to users of your application across multiple
Kinds, which is better the better approach assuming I don't need
locking for transactions?
a) store the "User" type (the actual User object) or
b) store a "Key" type (that was used as the Primary Key for a Kind
that stores user information)
For example, if the Kind AppUser is defined as...
@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class AppUser {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key key;
@Persistent
private User user;
...
}
and we're storing an image uploaded by that AppUser, is it better to
use:
Option (a)
@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class UploadedImage {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key key;
@Persistent
private User user;
...
}
or, Option (b)
@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class UploadedImage {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key key;
@Persistent
private Key appUserKey;
...
}
When retrieving 100s of images owned by the currentUser(), is option
(b) preferred even though it would require the initial lookup of the
AppUser before querying UploadedImage using appUserKey?
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