On 14/02/2011 18:10, Edson Tirelli wrote:

   The current version of Drools does not support dynamic changes in "type declarations" and I don't see this changing anytime soon. The reason is that not only the actual fact would require changes, but the actual knowledge base would require changes as several nodes might be referencing the old class.

   So, to update a fact type you need to recreate the knowledge base. This is the same, BTW, than changing one of your fact classes in your application jars... you need to recompile the knowledge base or you will end up with class cast exceptions, sooner or later.
Longer term there are two ways to achieve this
1) type declarations can only be modified if there is no data on them and the existing rules are still valid after the change, i.e. it will not effect the current state.

2) If ther eare existing facts a migration script must be provided that handles the mapping as all beans would need to be copied to the new type declaration.

Mark

    Edson

2011/2/14 delete <boyun.yuriy@gmail.com>

Hi.
I have such declaration of type
declare Contact
 firstName : String
end

then I want to add new property to this type. so the  next version is
declare Contact
 firstName : String
 newField : String
end

this type declaration is in separate drl file.
then I add this new type to current KnowledgeBase.
but when I execute knowledgeBase.getFactType("test.package", "Contact");
I get old version of Contact.

During debugging I found the place where is should be upgraded in the
KnowledgeBase.
org.drools.common.AbstractRuleBase.mergePackage
there is
// merge the type declarations
       if ( newPkg.getTypeDeclarations() != null ) {
           // add type declarations
           for ( TypeDeclaration type :
newPkg.getTypeDeclarations().values() ) {
               // @TODO should we allow overrides? only if the class is not
in use.
               if ( !pkg.getTypeDeclarations().containsKey(
type.getTypeName() ) ) {
                   // add to package list of type declarations
                   pkg.addTypeDeclaration( type );
               }
           }
       }

so according this comments it's not possible to upgrade Type on the fly.

Am I missing something?
Does someone had such problems or know the workaround.

Thanks in advance,
Yuriy

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--
  Edson Tirelli
  JBoss Drools Core Development
  JBoss by Red Hat @ www.jboss.com

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