Hi John,
thanks for your reply!
I'm trying to rewrite my code with ibis::table, as you suggested, but
I still have some doubts. Below there is a minimal example that I have
tried to write:
int main (int argc, char * argv [])
{
const char * dir = "database/";
ibis::table * table = ibis::table::create (dir);
ibis::table * selected = 0;
selected = table -> select ("SRC_PORT, DST_PORT", "SRC_PORT>20");
selected -> orderby ("SRC_PORT, DST_PORT");
/* Print the results */
selected -> dump (cout);
delete selected;
delete table;
return 0;
}
How can I use the DISTINCT statment in this example? What functions
should I use? Is there a function that returns a table with only
distinct rows?
I need to access only the distinct rows and iterate over them.
Any tips is appreciated,
thanks,
Valeria Lorenzetti
2010/3/29 K. John Wu <[email protected]>
>
> Hi, Valeria,
>
> The second way (in thula.cpp) might be better in general. The
> ibis::query object has some trouble with "count(*)". If you use
> ibis::query directly, it is best to leave out "count(*)". You can get
> the same information from the function ibis::query::getNumHits.
>
> John
>
>
> On 3/29/2010 1:19 AM, Valeria Lorenzetti wrote:
> > Hi John,
> > I saw that there are many ways to access Fastbit-data and run a query.
> >
> > From ibis.cpp:
> > ibis::query aQuery(uid, tbl);
> > aQuery.setWhereClause(wstr);
> > aQuery.setSelectClause(sstr);
> > aQuery.evaluate();
> > num1 = aQuery.getNumHits();
> >
> > From thula.cpp
> > ibis::table *sel = 0;
> > sel = tbl.select(sstr, wstr);
> > n1 = tbl.nRows();
> >
> >
> > I'd like to know what is the best way (faster and more flexible) to
> > manage the results. I need to apply efficiently some functions on
> > these, like DISTINCT, ORDERBY, LIMIT, etc. Moreover, I need to access
> > the rows individually to print them in a customized way (e.g. with an
> > XML format).
> >
> > At this time, to run a query, I'm using the first method:
> >
> > ibis::part part (directory, static_cast<const char*>(0));
> > ibis::query q (name,&part);
> > q.setSelectClause (select_clause);
> > q.setWhereClause (where_clause);
> > q.evaluate();
> >
> > To access and manage every single row, I'm using:
> > ibis::bundle * b = ibis::bundle::create (q);
> >
> > and to access every single value (i,j) of the row, to build a
> > customized output, I'm using:
> > b.getUInt (row-id, col-id);
> >
> >
> > However, I'm pretty sure that this is not the best way to manage the
> > results.
> > Can you give me some advice on the functions to use?
> >
> > Thanks in advance,
> > Valeria Lorenzetti
> > _______________________________________________
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> > [email protected]
> > https://hpcrdm.lbl.gov/cgi-bin/mailman/listinfo/fastbit-users
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