[storm] Fwd: Re: Re: multiple join's

[alexrichardson at gmail.com]

> On Jan 14, 2009 4:41pm, Gordon Allott gordallott at gmail.com> wrote:
> > On Wed, 2009-01-14 at 16:18 -0700, Alex Richardson wrote:
> >
> > > On Wed, Jan 14, 2009 at 3:56 PM, Gordon Allott gordallott at gmail.com>  
wrote:
> >
> > > Gordon,
> >
> > >
> >
> > > There are two different topics that I think your posting touches on.
> >
> > >
> >
> > > First is the question of who to use a join in a query. The tutorial
> >
> > > code you refer to properly demonstrates this. And it sounds like you
> >
> > > don't have any trouble getting the table join to work.
> >
> > >
> >
> > > The second question is how to build a 'where' clause to select the
> >
> > > appropriate rows. In the simple example above, you could use the
> >
> > > following code to find the companies for Ben, Steve, and Jon:
> >
> > >
> >
> > > origin = [Company, Join(Employee, Employee.company_id == Company.id)]
> >
> > > result = store.using(*origin).find(Company,
> >
> > > (Employee.name.like(u"Ben%") | (Employee.name.like(u"Ben%") |
> >
> > > (Employee.name.like(u"Ben%") ) )
> >
> > >
> >
> > > Note that the pipe operator '|' is shorthand for the more
> >
> > > verbose/explicit use of the 'Or' method.
> >
> > >
> >
> > > result = store.using(*origin).find(Company,
> >
> > > Or(Employee.name.like(u"Ben%"), (Employee.name.like(u"Ben%"),
> >
> > > (Employee.name.like(u"Ben%") ) )
> >
> > >
> >
> > > The use of 'and', 'or' and 'in', to build more complex where clauses
> >
> > > is touched upon in the storm manual.
> >
> > > (https://storm.canonical.com/Manual)
> >
> > >
> >
> > > Alex Richardson
> >
> >
> >
> > yes, but this method seems not to work, At the moment I am building up a
> >
> > list that looks similar to: (like is not actually needed in my
> >
> > situation)
> >
> > employees = [Employee.name == u'Ben', Employee.name == u'Steeve',
> >
> > Employee.name == u'John']
> >
> >
> >
> > neither of the following work:
> >
> > store.using(*origin).find(Company, *employees)
> >
> > store.using(*origin).find(Company, And(employees))
> >
> >
> >
> > although the following does:
> >
> > store.using(*origin).find(Company, Employee.name == u'Ben')
> >
> > # u'Steeve' and u'John' would work on their own also.
> >
> > --
> >
> > Gordon Allott (gordallott at gmail.com)
> >

Gordon, yes, the examples you are providing would not work. You need to  
provide a single where clause, so your first example does not work.
> store.using(*origin).find(Company, *employees)

Your second example uses an 'And' which means you are trying to match an  
employee row where the name is 'Ben' AND ' Steeve' AND 'John'. An  
employee's ame can not match all three values, so it always fails and you  
get back 0 rows.

However, if you change to an 'Or' it should work. Then you are trying to  
match an employee row where the name is 'Ben' OR ' Steeve' OR 'John'.

So I would expect something along the following to work:

> store.using(*origin).find(Company, Or(*employees))

Alex

PS Accidently sent this response directly to Gordon. Forwarding it to the  
list so someone can correct me if I'm wrong.
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