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@lists.jboss.org
[mailto:rules-users-bounces@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@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
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