[rules-users] Does Drools Fusion support "Group By" clause ?

[Wolfgang Laun]

On 4 January 2011 11:15, Gabor Szokoli <szocske at gmail.com> wrote:

> Hi,
>
> Purely for educational purposes I am trying to figure out how this
> will work when multiple Sale instances share the same "type" string.
>
> It seems to me that under the default "identity" assertion mode of the
> Working Memory, as many SaleType instances would be maintained as
> there are unexpired Sale events. In the degenerate case of all n Sale
> instances sharing the same type string, rules that bind a SaleType
> variable on their LHS should fire n times more than expected.
>

This is n - 1 times :-)

The fix is simple:

when
     Sale( $type : type )
     not SaleType( type == $type )
then
     insertLogical( new SaleType( $type ) );

-W


> Am I missing something?
>
> On the other hand "declare" creates a constructor with parameters? Neat!
>
> On Mon, Jan 3, 2011 at 4:28 PM, Edson Tirelli <ed.tirelli at gmail.com>
> wrote:
> >
> > declare SaleType
> >    type : String
> > end
> >
> > rule "register types"
> > when
> >     Sale( $type : type )
> > then
> >     insertLogical( new SaleType( $type ) );
> > end
> >
>
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