// This rule prints all objects in WM.
rule findObject
when
$o: Object()
then
System.out.println( "Object: " + $o );
end
Happily I get
Object: 42
Object: a String object
Object: org.drools.reteoo.InitialFactImpl@4dde85f0
Now the query way:
query object( Object o )
o := Object()
end
rule findObjectByQuery
when
object( $a ; )
then
System.out.println( "Object by query: " + $a );
end
Surprisingly, I get just one:
Object by query: org.drools.reteoo.InitialFactImpl@4dde85f0
A marvellous effect can be observed when the condition in rule
findObjectByQuery is modified to
when
Object()
object( $a ; )
then
I'd have guessed that the above result would appear repeatedly, once for
each Object in WM,
but that's not so. For N-1 facts the rule fires N*(N+1)/2 times, showing the
"initial object"
N times, the first inserted object N-1 times, the second one N-2 times and,
finally, the last one
once.
Object by query: 42
Object by query: org.drools.reteoo.InitialFactImpl@4dde85f0
Object by query: a String object
Object by query: 100
Object by query: 42
Object by query: org.drools.reteoo.InitialFactImpl@4dde85f0
Object by query: a String object
Object by query: org.drools.reteoo.InitialFactImpl@4dde85f0
Object by query: a String object
Object by query: org.drools.reteoo.InitialFactImpl@4dde85f0
-W
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