[jboss-jira] [JBoss JIRA] (DROOLS-651) Duplicate method call inside patterns

[Marc Dzaebel (JIRA)]

Marc Dzaebel created DROOLS-651:
-----------------------------------

             Summary: Duplicate method call inside patterns
                 Key: DROOLS-651
                 URL: https://issues.jboss.org/browse/DROOLS-651
             Project: Drools
          Issue Type: Bug
    Affects Versions: 6.2.0.Beta3
         Environment: Win7, Drools 6.2.0 Beta3 (probably all Drools versions)
            Reporter: Marc Dzaebel
            Assignee: Mark Proctor
            Priority: Minor


Create sample Drools project, add following method to the Message class:
{noformat}   public List<String> list() { 
      System.out.println("Call!");
      return Arrays.asList("one", "two"); 
   } {noformat}

sample.drl:
{noformat}
package com.sample
import com.sample.DroolsTest.Message;
import java.util.List;
import java.util.ArrayList;
 
rule ""
    when m : Message(L : list(), L.size>0)
    then System.out.println("L:"+L);
end
{noformat}
Running the project will result in the following output:
{noformat}
Call!
Call!
L:[one, two]
{noformat}

So _list()_ is called *two* times (duplicate). This may be due to the replacement of "L" with _list()_ in the second constraint. This is ok for simple +getters+ as here HotSpot optimizes this away. However, long running methods will produce unnecessary overhead, especially if further constraints on "L" are added (which I verified produce additional calls to list()). So at least methods with one or more arguments should be saved in temporary variables that should be used in further constraints. A fix of this problem will certainly accelerate Drools performance on similar patterns. If this is not feasible, at least a comment should be added to the documentation.



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