Default EOF behavior seems to assume that EOF objects are more valid
than those represented in the database. This attitude leads to
confusion for developers and makes the product harder to implement
efficiently.
>From the Tech Docs:
<...If a snapshot already exists with the same primary keys, EOF will
completely ignore the fetched row and just use the previous snapshot.
This appears to be undesirable since the new fetch might have updated
data. However, if the default was to always update the objects to the
latest fetched data, your objects might be updated at unknown and
invalid times. ...>
You are doing a fetch from the database -- I can't imagine a better time
to update changed objects. Why not set the default behavior to check
for changed snapshots and update EOFs accordingly? The
setRefreshesRefetchedObjects option is terribly inefficient as it causes
all snapshots (changed or not) to be updated.
<...The snapshots associated with an EOEditingContext is never
automatically released, even when the EOEditingContext is deallocated.
This means that as data is fetched from the database, the number of
snapshots, and hence your memory usage, will grow until you pull the
whole database into memory.
This is a known problem with EOF that will be addressed in future
releases....>
This is a direct result of mindset mentioned above. If you are not
going to trust the database to provide objects as they're needed, then
you have to keep every object you ever fetched -- in effect duplicating
the role of the database.
