[jboss-dev-forums] [Design of JBossCache] - Re: Possible optimization of CachedSetImpl
"genman" wrote : 1. I actually don't know the difference ... I may have
copied that from the original implementation. The tests seemed to pass. What's the
sematic difference?
attach/detach/find will go through the proper PojoCache interceptors (e.g., tx lock and
rollback). See pojocache-aop.xml for the corresponding stack.
anonymous wrote :
| 2. I'm not sure how this would work better?
|
| The need for offsetting the hashcode is to deal with a typically rare edge condition.
If the hash function is reasonably distributed, then the chances of hash code collision
(and therefore the need to do the hash code+1 trick) would be at best 1 in 2^32 and likely
only a few orders of magnitude worse otherwise.
|
| I think people expect hash collisions would happen more often, but that's because
in ordinary hash tables, collisions happen from evaluating (hash code % some small
number).
I am not talking about offsetting the hashcode. I like your implementation! What I was
referring to is the need to loop through the cache index consecutively, e.g., for
remove(), you have:
| for (int i = 0; i < size; i++)
| {
| Object key = toLong(hashCode, i);
| Object o2 = getNoUnmask(key);
| if (o2 == null)
| break;
| if (removed)
| {
| // move o2 to old key
| pCache_.detach(AopUtil.constructFqn(getFqn(), key));
| pCache_.attach(AopUtil.constructFqn(getFqn(), oldkey), o2);
| }
| if (o.equals(o2))
| {
| pCache_.detach(AopUtil.constructFqn(getFqn(), key));
| removed = true;
| }
| oldkey = key;
| }
| return removed;
|
insead of index looping, I could have like in pseudo code:
| // This is assumed to consist of only set objects.
| Collection list = cache.getNode(getFqn()).getChildren();
| for(Collection c: list)
| {
| // check if o is present
| Object o2 = cache.find(c);
| if(o == o2) cache.detach(c);
| return;
| }
|
This way, we don't maintain odered list of index.
BTW, the unit tests have some failure from the Set tests. I will probably need to look
into to see where they go wrong.
Thanks,
-Ben
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