Re: [Boost-users] [Boost][multi_index] proper way to make a complex query

From: Sebastien Fortier (sebastien.fortier_at_[hidden])
Date: 2006-08-08 15:13:14

I will definetly try what you have suggested and get back to you, thank 
you for your quick reply!

JOAQUIN LOPEZ MU?Z wrote:

> [...]
>
>
>Hello Sebastien,
>
>I'm not sure I've fully understood all the details of your problem,
>but seems to me that composite keys ( http://tinyurl.com/hdf3q )
>might be of help here. A composite key accepts several attributes
>and presents the records sorted in lexicographical order
>with respect to them. In your particular case, suppose you've
>got an index (non-unique) whose key is
>
>composite_key<
>  meteo_record,
>  const_mem_fun<meteo_record,const 
>string&,&meteo_record::get_grid_type>,
>  const_mem_fun<meteo_record,const 
>string&,&meteo_record::get_var_name>,
>  const_mem_fun<meteo_record,float,&meteo_record::get_ip2>,
>  const_mem_fun<meteo_record,int,&meteo_record::get_ip1Kind>,
>  const_mem_fun<meteo_record,float,&meteo_record::get_ip1>
>  
>
>
>(where I've used some imaginary names for the attribute getters).
>This index sorts records lexicographically by
>
>  grid_type,var_name,ip2,ip1Kind,ip1
>
>which looks like what you're after, from what I understand about
>the description of your current query process. The different
>groups can be then traversed like follows (for simplicity I
>assume the composite key is used in index #0, you'll probably want
>to have it in an additional index):
>
>for(recordIter=set.begin();recordIter!=set.end();)
>{
>  recordIter2=set.upper_range(
>    boost::make_tuple(
>      it->get_grid_type(),
>      it->get_var_name(),
>      it->get_ip2(),
>      it->get_ipKind(),
>    )
>  );
>
>  // [recorditer1,recorditer2) is a range of elements with equal
>  // grid_type,var_name,ip2 and ipKind, sorted by ip1
>  process(recordIter1,recordIter2);
>  
>  recordIter1=recordIter2;
>}
>
>Is this what you were looking for? Thank you for using
>Boost.MultiIndex,
>
>Joaquín M López Muñoz
>Telefónica, Investigación y Desarrollo
>_______________________________________________
>Boost-users mailing list
>Boost-users_at_[hidden]
>http://lists.boost.org/mailman/listinfo.cgi/boost-users
>
>  
>

-- 
Sébastien Fortier
Analyste-Programmeur
Centre Météorologique Canadien
2121, voie de service nord, Trans-Canadienne
Dorval, QC
H9P 1J3
Tel: [phone]    Fax: [phone]
Courrier électronique:  _ Sebastien.Fortier_at_[hidden]_