[rules-users] does WorkingMemory.iterator support remove()?

[Mark Proctor]

Anstis, Michael (M.) wrote:
> Wouldn't the best approach be to get the FactHandles iterator and retact
> them from working memory rather than removing them through the iterator?
>
> Iterator itr = wm.iterateFactHandles();
> While(itr.next()) {
> 	FactHandle h = itr.next();
> 	wm.retract(h);
> }
>
> This would ensure truth maintenance is preserved.
>   
Actually I'm not sure that would be safe.... the objects and the handles 
are in the same hashtable. Those internal data structures where built 
for performance and lightweightness, not thread safeness and mutability. 
If you actually look we have an internal, fast, iterator which we simple 
adapt to a slower java.util.Iterator. At the moment none of our 
iterators are thread safe, but I do see a valid use case here, we will 
have to think on it for the next major release - cleam implementation 
patch welcome with unit tests :) I'm less concerned about the iterator 
adapter performance, but I cannot compromise on the performance of our 
internal iterators.

    public static class HashTableIterator
        implements
        Iterator {

        private static final long serialVersionUID = 400L;

        private AbstractHashTable hashTable;
        private Entry[]           table;
        private int               row;
        private int               length;
        private Entry             entry;

        public HashTableIterator(final AbstractHashTable hashTable) {
            this.hashTable = hashTable;
        }

        /* (non-Javadoc)
         * @see org.drools.util.Iterator#next()
         */
        public Object next() {
            if ( this.entry == null ) {
                // keep skipping rows until we come to the end, or find 
one that is populated
                while ( this.entry == null ) {
                    this.row++;
                    if ( this.row == this.length ) {
                        return null;
                    }
                    this.entry = this.table[this.row];
                }
            } else {
                this.entry = this.entry.getNext();
                if ( this.entry == null ) {
                    this.entry = (Entry) next();
                }
            }

            return this.entry;
        }

        /* (non-Javadoc)
         * @see org.drools.util.Iterator#reset()
         */
        public void reset() {
            this.table = this.hashTable.getTable();
            this.length = this.table.length;
            this.row = -1;
            this.entry = null;
        }
    }
> -----Original Message-----
> From: rules-users-bounces at lists.jboss.org
> [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Godmar Back
> Sent: 05 October 2007 16:40
> To: Rules Users List
> Subject: Re: [rules-users] does WorkingMemory.iterator support remove()?
>
> Thanks - consider supporting it for efficiency. (Otherwise, removing a
> set of facts from working memory requires a temporary container to
> hold the facts to be removed.)
>
>  - Godmar
>
> On 10/5/07, Mark Proctor <mproctor at codehaus.org> wrote:
>   
>> Godmar Back wrote:
>>     
>>> Does the iterator returned by WorkingMemory.iterator support remove()?
>>>
>>> I checked the javadoc and the Drools manual, but may have missed it.
>>>
>>>       
>> If you try it you'll get an exception thrown
>>     
> "UnsupportedOperationException"
>   
> http://anonsvn.labs.jboss.com/labs/jbossrules/trunk/drools-core/src/main/jav
> a/org/drools/util/JavaIteratorAdapter.java
>   
>>> Please answer and augment documentation.
>>>
>>>  - Godmar
>>> _______________________________________________
>>> rules-users mailing list
>>> rules-users at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/rules-users
>>>
>>>
>>>       
>> _______________________________________________
>> rules-users mailing list
>> rules-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>>     
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>   
> ------------------------------------------------------------------------
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>   

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-users/attachments/20071005/8ac8dbdc/attachment.html