Rip, I'm still not persuaded that this is not a bug. Regarding this -
> "s.last.name" the query is updated with #last, so now the query is
> like this: User.all(:order => [:age.asc]).last => which is like
> User.all(:order => [:age.asc]).update(:limit => 1, :order =>
> [:age.desc])
I agree with your description of what the query required to retrieve
the last element looks like, but there's nothing in the API
documentation to suggest that #last modifies its receiver in the
process. Rather it says that it *returns* the "last resource in the
entries of this collection, or a new collection whose query has been
merged". This is contrast to the documentation for #update which
states explicitly that it returns 'self'.
I agree that #last does seem to be modifying the query associated with
the collection it is called on, but I don't see any reason that this
would be the intended behavior.
On Mar 3, 7:56 pm, RipTheJacker <kab...@gmail.com> wrote:
> It's calling an extra query and leaving it there:
>
> "first query
> ~ (0.000097) SELECT "id", "age", "name" FROM "users" ORDER BY "age"
> ["Jill", "Mary", "Bob", "Jack"]
> "Jack"
> ["Jill", "Mary", "Bob", "Jack"]
> second query
> ~ (0.000081) SELECT "id", "age", "name" FROM "users" ORDER BY "age"
> DESC LIMIT 1
> "Jack"
> ~ (0.000078) SELECT "id", "age", "name" FROM "users" ORDER BY "age"
> DESC
> ["Bob", "Mary", "Jill", "Jack"]"
>
> I don't think it is a bug, here's how it works:
>
> "s = User.all(:order => [:age.asc])"
> "s" is just a DataMapper::Query until you call something on it.
> "s.map{|r| r.name}" <- now you've called something so the query
> executes here.
> "s" is now a reference to a DataMapper::Collection, because you called
> the query
> "s.last.name" -> #last is calling DataMapper::Collection#last
>
> In the second part:
> "s = User.all(:order => [:age.asc])"
> "s" again is just a query at this point
> "s.last.name" the query is updated with #last, so now the query is
> like this: User.all(:order => [:age.asc]).last => which is like
> User.all(:order => [:age.asc]).update(:limit => 1, :order =>
> [:age.desc]) because DM will give you the "last result in users sorted
> by age asc" which is the same as saying the "first result in users
> sorted by age desc"
>
> Here's how it -might- be a bug... (in the second example)
> "s" is a reference to an updated query as opposed to a single User
> instance, or it might be a collection, I don't know here...
> "s.map{|r| r.name}" #map is being called on the updated query
>
> On Feb 28, 11:01 pm, MarkMT <mark.thom...@ieee.org> wrote:
>
> > Sorry, I pasted the url for another gist I had been looking at from a
> > different thread. This is the one I meant to refer to -
>
> >http://gist.github.com/318072
>
> > On Feb 28, 10:57 pm, MarkMT <mark.thom...@ieee.org> wrote:
>
> > > I've run into a problem that seems like it might be a bug...
>
> > > If I retrieve a set of records using the ':order' option and then call
> > > 'last' on the resulting collection, the collection seems to end up
> > > being mis-ordered. The problem only seems to manifest itself if I
> > > haven't made an attempt to do anything with the ordered collection
> > > prior to calling 'last'.
>
> > > Here's a gist that illustrates -http://gist.github.com/305019.
>
> > > This is with dm 0.10.2. Am I misunderstanding how this should work?
>
> > > Mark.
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