[rules-users] Using rules with database scenario

[hypnosat7]

Did you find any ideas to deal with a large data base system ?
Thanks


Joe Chuby wrote:
> 
> Thanks all for replying. 
> 
> We currently already have a layer of service (DAO) to retrieve data from
> the database. We were thinking along the line you suggested there, but
> somehow, we have the impression that it's not quite as efficient as we
> would like. 
> 
> If we were to load the data from the database so that Rules can pick those
> we wanted, we would have to load records in the range of hundreds of 
> thousands (or even more), which would kill our system there. It would be
> much less expensive to do this with a single query statement.
> 
> Right now, we are thinking along the line of, say, letting the rules
> generate
> a query statement on the fly, based on the result from firing the rules.
> But that's
> much more complicated to achieve that just writing the SQL directly.
> 
> Now, to make things more complicated (as per the business requirements), 
> if we use rules, we have to run parts of the rules first, retrieve parts
> of the 
> data, then run the second part of the rules (which use the first part of
> data 
> to make decision), then retrieve next part of data, and so on. This does
> not 
> seem like an efficient way though. With SQL, we could write a more or less
> complicated statement (with sub-queries and the usual suspect), and get 
> the final result in one shot.
> 
> The major issue we have with rules is that it assumes all data necessary
> for
> firing the rules are in memory. This works fine for small systems (and
> with small
> number of users). But right now, we couldn't figure out an efficient way
> to work
> with large amount of data already in the database.
> 
> Maybe we are are not thinking in the right line of reasoning. Please help
> to
> point out what's wrong.
> 
> If someone had experience dealing with large database system and is
> willing to
> share the experience, that would be really appreciated.
> 
> We are currently using Rules v3.0.5. Will try the v3.1.0.
> 
> Best,
> 
> Marcus Ilgner <marcus.ilgner at gmail.com> wrote:
> That's probably the best solution. Using the current version (3.1M1),
> you can use the FROM keyword to reference facts from List object
> returned from a method call on a service, for example.
> Something like this works very good in my current testing project:
> 
> rule foobar
> when
>   MyObject( someValue = "foobar" ) from MyObjectDAO.loadAll()
> then
> ...
> end
> 
> The DAO then uses Hibernate to load some objects and returns a
> List which can be used by Drools.
> As Uday already wrote, you could also write a DAO which retrieves
> arbitrary objects using a given HQL statement.
> 
> Best regards
> Marcus
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