[rules-users] Drools - Query Problem

[Pavel Tavoda]

Another "simple" way will be to declare global variable like:
global List EBandRating;

and in then clause you can do:
EBandRating.add(r);

You don't have to make queries, no-loops, lock-on-active or other tricky stuff.

Pavel

2010/3/29 Esteban Aliverti <esteban.aliverti at gmail.com>:
> Hi,
> What Wolfgang is trying to say about "inform" the Drools engine about the
> update is that you need to use a modify statement in your RHS. Your rule
> should look like this:
> rule "for E band"
>         lock-on-active true
>         when
>                 r : Rating( rate == 1)
>         then
>                                 modify(r){
>                    setBand("EBand");
>                                 }
>                 System.out.println( "in E band" );
> end
> This is the way to inform Drools that your Fact is modified. But be careful,
> because when you modify a Fact, all the rules are evaluated again because
> the modification could activate another Rule. This will end in an infinite
> loop (just like Wolfgang mentioned), the "for E band" rule will be executed
> for ever. That's why you need to add the no-loop attribute (if the only rule
> that modifies a Rating is "for E band") or lock-on-active (if more than one
> rule could modify a Rating).
> On Mon, Mar 29, 2010 at 7:20 AM, Wolfgang Laun <wolfgang.laun at gmail.com>
> wrote:
>>
>> You have to inform the Drools engine about the update done with
>> r.setBand("..."), or else the query condition is still seeing the fact
>> state at insert time.
>>
>> You may have to add the no-loop option to your rules.
>>
>> (Also, comments and actions disagree, e.g. "D Band" vs. "EBand")
>>
>> -W
>>
>> On 3/29/10, Nilima R <nilima.r at tcs.com> wrote:
>> > Dear All,
>> >
>> > I have created simple rule file and created model in that rule file only
>> >
>> > package com.sample
>> >
>> > import java.lang.String;
>> >
>> > declare Rating
>> > rate : int
>> > band : String
>> > name : String
>> > end
>> >
>> > query "employee with band E"
>> > ratg : Rating(band == "EBand")
>> > end
>> >
>> > rule "for E band"
>> >
>> >         when
>> >                 r : Rating( rate == 1)
>> >         then
>> >                 r.setBand("EBand");
>> >                 System.out.println( "in E band" );
>> >
>> > end
>> >
>> > rule "for D band"
>> >
>> >         when
>> >                 r : Rating( rate == 2)
>> >         then
>> >                 r.setBand("EBand");
>> >                 System.out.println( "in E band" );
>> >
>> > end
>> >
>> > rule "for C band"
>> >
>> >         when
>> >                 r : Rating( rate == 3)
>> >         then
>> >                 r.setBand("EBand");
>> >                 System.out.println( "in E band" );
>> >
>> > end
>> >
>> > rule "for B band"
>> >
>> >         when
>> >                 r : Rating( rate == 4)
>> >         then
>> >                 r.setBand("EBand");
>> >                 System.out.println( "in E band" );
>> >
>> > end
>> >
>> >
>> > At the end I want to know how many employees have got E band and so have
>> > written query for it in the rule file .and obtained the query results as
>> > below
>> >
>> >
>> > FactType bandType = kbase.getFactType( "com.source", "Rating" );
>> >                         QueryResults results = ksession.getQueryResults(
>> > "employee with band E");
>> >                         System.out.println( "we have " + results.size()
>> > +
>> > "employee with band E" );
>> >                         System.out.println( "employee with band E:" );
>> >
>> >                         for (Iterator i = results.iterator();
>> > i.hasNext();) {
>> >                             QueryResultsRow row =
>> > (QueryResultsRow)i.next();
>> >                             Object ratg = row.get("rating");
>> >                             String name = (String) bandType.get( ratg,
>> > "name" );
>> >                             System.out.println(name);
>> >                          }
>> >
>> >
>> > But am getting the result of query as 0 records.
>> >
>> >
>> > i am inserting objects one by one ( this for testing just purpose ) to
>> > learn how query works.
>> >
>> >
>> > Can someone plz point out what is wrong.Its Urgent ................
>> >
>> >
>> > Thanks in advance.
>> > Nilu
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>
>
> --
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>
> Esteban Aliverti
>
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