[rules-users] Help with MatchesEvaluatorsDefinition that caches compiled regular expression patterns

[Edson Tirelli]

   Jared,

   Your idea is actually interesting. Although, we would need to take care
of a few edge scenarios:

* The actual evaluator instance is supposed to be a "fly weight"
implementation, and as so, it might be used by multiple threads. So, first
thing, the cache map implementation must be thread safe.

* We had problems in the past when using static caches like that in
JEE/Spring/OSGi environments where you have multiple modules being loaded by
different classloaders etc. So, I think best would be to have a non-static
map for each: the StringMatchesEvaluator and the StringNotMatchesEvaluator
inner classes.

* We need a way to clean up the cache for no-longer used expressions.
Easiest way would probably be to use an LRU map as cache. The size of the
cache would probably have to be a configuration on the
KnowledgeBaseConfiguration, with a given default value. This would avoid
memory leaks.

   Wanna try providing a patch for that?

   Thanks,
       Edson

2009/5/4 Jared Davis <sunray at davisprogramming.com>

> I need some help placing a cache of compiled regular expressions using the
> MatchesEvaluatorsDefinition as a starting point.
>
> Just for a test I placed a static map in the class:
>
> static Map<String,Pattern> uglyHack = new HashMap<String,Pattern>();
>
>
> Then in each of the evaluators I have different versions of:
>
>        Pattern p = uglyHack.get(value2);
>        if (p == null ) {
>            p = Pattern.compile(value2);
>            uglyHack.put(value2, p);
>        }
>        Matcher m = p.matcher(value1);
>        return m.matches();
>
> instead of
>
>
>        return value1.matches( value2 );
>
>
> The time elapsed to inserting objects into the workspace has been cut in
> half.
>
> .4 seconds -> .2
>
> Has someone already done this "optimization?" Where should the cache be
> stored?
>
>
>
>
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>



-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss, a division of Red Hat @ www.jboss.com
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