[infinispan-dev] keySet(), values() and entrySet() not implemented

[Manik Surtani]

On 4 Jun 2009, at 10:12, Mircea Markus wrote:

> Galder Zamarreno wrote:
>> Hi,
>>
>> keySet(), values(), entrySet() do not seem to be implemented at the  
>> moment:
>>
>>   public Set<K> keySet() {
>>      throw new UnsupportedOperationException("TODO implement  
>> me"); // TODO implement me
>>   }
>>
>>   public Collection<V> values() {
>>      throw new UnsupportedOperationException("TODO implement  
>> me"); // TODO implement me
>>   }
>>
>>   public Set<Map.Entry<K, V>> entrySet() {
>>      throw new UnsupportedOperationException("TODO implement  
>> me"); // TODO implement me
>>   }
>>
>> We should be implementing these methods, shouldn't we? Users might  
>> want to iterate the map for example to print the contents or to  
>> verify it contains what they put on it...etc.
>>
>> I can't see a JIRA for it, so I'll open one so that this gets  
>> implemented for Beta1 unless someone has any objections.
>>
>> On IRC, Mircea said it might very costly, specially for dist, but  
>> we still need it regardless, otherwise we're not fully implementing  
>> the ConcurrentMap interface and these are commonly used methods.
> for DIST these might be implemented as follows:
> -the node broadcasts a 'GetKeys' command to all others nodes in the  
> cluster
> - on remote nodes locks are acquired for all keys (not sure this  
> mandatory though)
> - each node responds with the set of keys
> - calling node puts them together and returns them to the user
>
> for entrySet this is even more costly, as all cluster state shall be  
> transfered to the calling node.
> Now, what worries me is the fact that users might overuse these  
> methods, without being aware of the performance consequences.

I think such consequences should be clearly Javadoc'd, as well as  
mentioned in FAQs.

> A possible way to enforce the users to acknowledge that these  
> operations are costly, is to disable them by default and allow a  
> config element to enable them.

Not sure if I like this approach - since it breaks the ConcurrentMap  
contract by default.

Cheers
--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org