Le 4/27/12 2:09 PM, Selcuk AYA a écrit :
Hi,
On Thu, Apr 26, 2012 at 4:52 PM, Emmanuel Lécharny<[email protected]> wrote:
Hi guys,
currently, we can replace an existing value when its associated key exists
in the BTree. What I'd like to do is to replace both key and value in this
case.
The rational is that the key mau contain some extra information that are not
used to find the key, like the nbChildren/nbDescendant for a ParentIdAndrdn
key in the RdnIndex.
Is there an easy way to do that with JDBM, or should we extend the API it
offers ?
as I understand you are trying to store some auxiliary information per
key?
Yep.
With JDBM we can:
- provide<K, aux> tuple as the key and pass the key comparator to
be the comparator for the actual keys.
- change JDBM code to update key inside when replacing an entry.
however, in general, I do not think we can expect a key/value store to
update the key when replacing an entry. So I am not sure it is a good
idea to do this kind of thing.
The pb is that those auxiliary informations are not part of the compare
being done. Ie, two keys may be seen as equals, but the auxiliary
information might be different. In this very case, I'd like the new
version of the key replaced.
It may be very specific to my need, and we can also consider that the
value might cary those extra informations, too, instead of storing them
in the key.
So for the <ParentIdAndRdn, ID> tuple, where the data structure is :
ParentIdAndRdn :
{
ID parentId,
Rdn[] rdns,
int nbChildren,
int nbDescendant
}
we could inject the two ints after having read the value if this value
structure was :
AugmentedID
{
ID id
int nbChildren,
int nbDescendant
}
and serializing the ParentIdAndRdn ID and Rdn[] only.
That may work...
thoughts ?
--
Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com
