Exactly, I also thought of generating an internal enum of attribute
keys. From there we can either use an EnumMap wrapper of object[] or
just the array.
Andrus
On Nov 30, 2009, at 12:23 PM, Tore Halset wrote:
Hello.
Would it be possible to have attributes within an entity as enum and
then use EnumMap? It uses an array for storage, so it does not need
the buly Map.Entry objects used in a normal HashMap.
- Tore.
On Nov 30, 2009, at 11:09 , Andrus Adamchik wrote:
Another possible "lightweight" design that would allow to reconcile
DO's and PO's is to use Object[] instead of either HashMap or ivars
to store values, with indexes in array corresponding to
ObjAttribute names sorted in alphabetic order. Will probably have
its own quirks I guess (e.g. how do we define the array size for a
generic object that can be mapped to different entities), however
it has some serious benefits:
* memory use very close to ivars
* access speed very close to ivars
* can be used with Faults
* can be used with generic objects
Andrus
On Nov 24, 2009, at 9:47 PM, Andrus Adamchik wrote:
True, but they are still user facing collections (or more
generally valueholders, as this also works for to-one), that get
inflated internally as needed. DO faults are singletons of this
type:
http://cayenne.apache.org/doc/api/org/apache/cayenne/Fault.html
So PO lazy relationship resolving goes like this:
1. on select, init lazy property with a "hollow" ValueHolder
2. on ValueHolder value access, inflate ValueHolder with the DB data
For DO it has an extra step:
1. on select, init lazy property with a singleton Fault of a type
corresponding to the relationship semantics
2. on property access, *replace* Fault with either a hollow
collection or a target DO (which can be hollow or resolved from
cache)
3. on collection or hollow DO value access, inflate them.
The difference may be subtle, but still essential. First, in DO
case there's no to-one ValueHolder. Target object is attached
directly. Also the user never sees the Fault object itself, so we
can replace it with another object when needed. Among other things
this allows a major memory optimization, as Fault instances are
singletons shared by all DOs.
So all in all, DO design seems more sound (and quite possibly that
whatever memory we save on using ivars in PO, is getting lost to
extra and more eager ValueHolders).
Andrus
On Nov 24, 2009, at 9:28 PM, Andrey Razumovsky wrote:
Actually, I don't understand :) PO arc properties are all faults
(classes
PersistentObject*)
2009/11/24 Andrus Adamchik <[email protected]>
On Nov 24, 2009, at 5:14 PM, Andrey Razumovsky wrote:
So ... another attempt at abstract analysis (or an attempt at
unwinding
my
memory...) IIRC the main difference between DO and PO is fault
handling -
we
can store a Fault instance in a map, but not in a typed ivar.
So PO's
have
no concepts of faults at all, and the lifecycle is different.
DO approach
is
more lazy (it won't try to create even a placeholder
collection until the
property is accessed), and I prefer it to PO's. Wonder if when
we
reconcile
that somehow, the rest will fall into place on its own??
(E.g. for PO's, we generate extra boolean "fault" properties
for each
relationship, that are checked on every property access?)
Nice idea, need to think about it. But anyways, this is
separate task
May or may not be a separate task. But definitely bigger in scope.
Andrus
--
Andrey
