[rules-users] Buggy query behavior in drools 5.6 and 6.1-SNAPSHOT ??

[Esteban Aliverti]

Hi guys,
I was writing some rules using backward chaining and found a strange
behavior.
I managed to isolate the error in the test project I'm attaching.

In the project I have 2 classes: Parent and Child

Parent:
    * String id
    * String attribute1
    * String attribute2
    * List<Child> children

Child:
    * String parentId;
    * String name;
    * String value;


In the test I'm creating 1 Parent object with just 1 child and then
inserting the Parent object into a drools session:

        Parent p1 = new Parent();
        p1.setId("1");
        p1.setAttribute1("a1");
        p1.setAttribute2(null);

        Child c1p1 = new Child();
        c1p1.setName("n1");
        c1p1.setParentId(p1.getId());
        c1p1.setValue("v1.1");
        p1.addChild(c1p1);

        kSession.insert(p1);
        kSession.fireAllRules();


So far so good.
The rules I have in my session are the following:

declare Parent
    @propertyReactive
end

query getChildWithName(String $parentId, String $name, Child $child)
    $child:= Child(parentId == $parentId, name == $name)
end

rule "Insert Children"
when
    $p: Parent()    @watch(!*)
    $c: Child() from $p.children
then
    System.out.println("Inserting child "+$c);
    insert($c);
end

rule "Rule A"
when
    $p: Parent(attribute2 != null)
    ?getChildWithName($p.attribute2, "n1", $child;)
then
    System.out.println("FOUND: "+$child+". The attribute 'parentId' of this
object must have the value '"+$p.getAttribute2()+"'. Does it?
"+$child.getParentId()+" == "+$p.getAttribute2()+" ??");
    globalList.add($child);
end


rule "Copy Attribute1 into Attribute2"
when
    $p: Parent(attribute1 != null, attribute2 == null)
then
    modify($p){
        setAttribute2($p.getAttribute1())
    }
end

The important part here is 'Rule A' and 'Copy Attribute1 into Attribute2'.
The latter copies the value of attribute1 to attribute2 for any Parent
object present in the session. (Note that the parent I'm inserting has
attribute2 = null). 'Rule A' is then using a query to get a Child object
that has a parent with id = $p.attribute2 (where $p is a previously matched
Parent).
Given that I only have 1 Parent in my session and that its id is '1' I
don't expect 'Rule A' to be activated/executed. When I modify
parent.attribute2 in 'Copy Attribute1 into Attribute2' I'm setting its
value to 'a1'. 'Rule A' (via the query) should then look for a Child with
parentid = 'a1' and It shouldn't find anything.
Funny thing is that 'Rule A' activates and fires. The child object that is
'returned' by the query has a parentId of '1' so I don't know how this
behavior is possible. If you take a look at the System.out output you will
see that the activation makes no sense at all.

Am I doing something wrong in my project? Is this a bug? Is this the
expected behavior?

Regards,



XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Esteban Aliverti
- Blog @ http://ilesteban.wordpress.com
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