Does the iterator returned by WorkingMemory.iterator support remove()? I checked the javadoc and the Drools manual, but may have missed it.

Please answer and augment documentation. - Godmar _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

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

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.

-----Original Message----- From: rules-users-bounces(a)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(a)codehaus.org&gt; 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(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/rules-users >> >> >> > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > > _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users ------------------------------------------------------------------------ _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

Excuse me if this would be best posted to the developer list... ...but let me undertstand: The Fact table maintained for a WorkingMemory is not thread safe(?); however WorkingMemories are thread safe - suggesting Shadow Facts and (excuse my vague terminolgy) Node Memories are the thread safe aspect of working memories - the Fact table containing references to the original inserted objects not the Shadows. So if a Fact is removed using my "unsafe" code it will cause Shadow Facts to become disconnected from their original non-shadowed Fact? Would using ThreadLocal storage for the Fact table (together with node memories and shadow facts) mean a complete thread-safe Drools? I don't mean this to become a tutorial in either Drools threading or general java thread safety!! (I don't think there's a category on the "how to have your emails ignored" listing for this). I just want to increase my awareness of (Drools) threading issues... and this proves a good example. On 05/10/2007, *Mark Proctor* <mproctor(a)codehaus.org <mailto:mproctor@codehaus.org>> wrote: 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(a)lists.jboss.org <mailto: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(a)codehaus.org&gt; <mailto: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 > <http://anonsvn.labs.jboss.com/labs/jbossrules/trunk/drools-core/src/main/... > a/org/drools/util/JavaIteratorAdapter.java > >>> Please answer and augment documentation. >>> >>> - Godmar >>> _______________________________________________ >>> rules-users mailing list >>> rules-users(a)lists.jboss.org <mailto:rules-users@lists.jboss.org> >>> https://lists.jboss.org/mailman/listinfo/rules-users >>> >>> >>> >> _______________________________________________ >> rules-users mailing list >> rules-users(a)lists.jboss.org <mailto:rules-users@lists.jboss.org> >> https://lists.jboss.org/mailman/listinfo/rules-users >> >> > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org <mailto:rules-users@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/rules-users > > ------------------------------------------------------------------------ > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org <mailto:rules-users@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/rules-users > _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org <mailto:rules-users@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/rules-users <https://lists.jboss.org/mailman/listinfo/rules-users> ------------------------------------------------------------------------ _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users