Betternestedset talk - Jul 2007 - Display whole tree without requesting db for each node

Hi!
I?m wondering how I display the whole tree without having to request the 
db each time I use @node.level.
Thanks!
/Jonas

Hi,

Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
> I?m wondering how I display the whole tree without having to  
> request the
> db each time I use @node.level.
You have to cache the level in db, or simply compute it in code after  
you read your tree part.

Jean-Christophe Michel
--
symetrie.com

Better Nested Set for rails:
http://opensource.symetrie.com/trac/better_nested_set

This is something I''ve wondered also as it more or less cancels out any
speed gain from getting the full set in one query. Does betternestedset
provide the hooks to cache the level? Alternatively, the parent_id could
theoretically be used to calculate levels from a full set. 



-----Original Message-----
From: betternestedset-talk-bounces at rubyforge.org
[mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of
Jean-Christophe Michel
Sent: 23 July 2007 22:02
To: betternestedset-talk at rubyforge.org
Subject: Re: [Betternestedset-talk] Display whole tree without
requesting dbfor each node


Hi,

Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
> I?m wondering how I display the whole tree without having to
> request the
> db each time I use @node.level.
You have to cache the level in db, or simply compute it in code after  
you read your tree part.

Jean-Christophe Michel
--
symetrie.com

Better Nested Set for rails:
http://opensource.symetrie.com/trac/better_nested_set


_______________________________________________
Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
http://rubyforge.org/mailman/listinfo/betternestedset-talk

If you have this as an ongoing requirement, a "simple" solution might
be storing the level in the model itself in an after save call back.

It''s a bit of a hack, but you can only move the nodes through update
calls anyway... so it might work.  Then you have it automagically as
an instance method.

Regards

Mikel

On 7/25/07, Tekin Suleyman <tekin at raid.nu>
wrote:
>
> This is something I''ve wondered also as it more or less cancels
out any
> speed gain from getting the full set in one query. Does betternestedset
> provide the hooks to cache the level? Alternatively, the parent_id could
> theoretically be used to calculate levels from a full set.
>
>
>
> -----Original Message-----
> From: betternestedset-talk-bounces at rubyforge.org
> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of
> Jean-Christophe Michel
> Sent: 23 July 2007 22:02
> To: betternestedset-talk at rubyforge.org
> Subject: Re: [Betternestedset-talk] Display whole tree without
> requesting dbfor each node
>
>
> Hi,
>
> Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
> > I?m wondering how I display the whole tree without having to
> > request the
> > db each time I use @node.level.
>
> You have to cache the level in db, or simply compute it in code after
> you read your tree part.
>
> Jean-Christophe Michel
> --
> symetrie.com
>
> Better Nested Set for rails:
> http://opensource.symetrie.com/trac/better_nested_set
>
>
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
> _______________________________________________
> Betternestedset-talk mailing list
> Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>

Why didn''t I think of that! I''ll give it a try.

-----Original Message-----
From: betternestedset-talk-bounces at rubyforge.org
[mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Mikel
Lindsaar
Sent: 25 July 2007 00:20
To: betternestedset-talk at rubyforge.org
Subject: Re: [Betternestedset-talk] Display whole tree without
requestingdbfor each node


If you have this as an ongoing requirement, a "simple" solution might
be
storing the level in the model itself in an after save call back.

It''s a bit of a hack, but you can only move the nodes through update
calls anyway... so it might work.  Then you have it automagically as an
instance method.

Regards

Mikel

On 7/25/07, Tekin Suleyman <tekin at raid.nu>
wrote:
>
> This is something I''ve wondered also as it more or less cancels
out
> any speed gain from getting the full set in one query. Does 
> betternestedset provide the hooks to cache the level? Alternatively, 
> the parent_id could theoretically be used to calculate levels from a 
> full set.
>
>
>
> -----Original Message-----
> From: betternestedset-talk-bounces at rubyforge.org
> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of 
> Jean-Christophe Michel
> Sent: 23 July 2007 22:02
> To: betternestedset-talk at rubyforge.org
> Subject: Re: [Betternestedset-talk] Display whole tree without 
> requesting dbfor each node
>
>
> Hi,
>
> Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
> > I?m wondering how I display the whole tree without having to request
> > the db each time I use @node.level.
>
> You have to cache the level in db, or simply compute it in code after 
> you read your tree part.
>
> Jean-Christophe Michel
> --
> symetrie.com
>
> Better Nested Set for rails: 
> http://opensource.symetrie.com/trac/better_nested_set
>
>
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
_______________________________________________
Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
http://rubyforge.org/mailman/listinfo/betternestedset-talk

I?m a littlebit confused. But how do i accomplish that? Storing level 
inside db that is.

Tekin Suleyman skrev:
> Why didn''t I think of that! I''ll give it a try.
>
> -----Original Message-----
> From: betternestedset-talk-bounces at rubyforge.org
> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Mikel
> Lindsaar
> Sent: 25 July 2007 00:20
> To: betternestedset-talk at rubyforge.org
> Subject: Re: [Betternestedset-talk] Display whole tree without
> requestingdbfor each node
>
>
> If you have this as an ongoing requirement, a "simple" solution
might be
> storing the level in the model itself in an after save call back.
>
> It''s a bit of a hack, but you can only move the nodes through
update
> calls anyway... so it might work.  Then you have it automagically as an
> instance method.
>
> Regards
>
> Mikel
>
> On 7/25/07, Tekin Suleyman <tekin at raid.nu> wrote:
>   
>> This is something I''ve wondered also as it more or less
cancels out
>> any speed gain from getting the full set in one query. Does 
>> betternestedset provide the hooks to cache the level? Alternatively, 
>> the parent_id could theoretically be used to calculate levels from a 
>> full set.
>>
>>
>>
>> -----Original Message-----
>> From: betternestedset-talk-bounces at rubyforge.org
>> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of 
>> Jean-Christophe Michel
>> Sent: 23 July 2007 22:02
>> To: betternestedset-talk at rubyforge.org
>> Subject: Re: [Betternestedset-talk] Display whole tree without 
>> requesting dbfor each node
>>
>>
>> Hi,
>>
>> Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
>>     
>>> I?m wondering how I display the whole tree without having to
request
>>>       
>
>   
>>> the db each time I use @node.level.
>>>       
>> You have to cache the level in db, or simply compute it in code after 
>> you read your tree part.
>>
>> Jean-Christophe Michel
>> --
>> symetrie.com
>>
>> Better Nested Set for rails: 
>> http://opensource.symetrie.com/trac/better_nested_set
>>
>>
>> _______________________________________________
>> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
>> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>>
>> _______________________________________________
>> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
>> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>>
>>     
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
> _______________________________________________
> Betternestedset-talk mailing list
> Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
>

This isn''t actually as straight forward as it might seem. It
can''t be
done in an after_save call back as you end up in an infinite loop. I
thought you might be able to do it in a before_save, something like:

before_save :cache_level
alias_method :old_level, :level
def level() self.level_cache; end

private
def cache_level
  self.level_cache = self.old_level
End

And make sure you have a column in your table called level_cache. Now,
when you call object.level, it won''t make a db call to calculate the
level, it will simply return the level_cache attribute.

But I''m now not convinced it will exhibit correct behaviour - if
old_cache is called before the object is updated, it will cache the
current and not the new level, right?

Any thoughts?

Tekin



-----Original Message-----
From: betternestedset-talk-bounces at rubyforge.org
[mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Jonas
Arklint
Sent: 06 August 2007 09:29
To: betternestedset-talk at rubyforge.org
Subject: Re: [Betternestedset-talk] Display whole tree without
requestingdbfor each node


I?m a littlebit confused. But how do i accomplish that? Storing level 
inside db that is.

Tekin Suleyman skrev:
> Why didn''t I think of that! I''ll give it a try.
>
> -----Original Message-----
> From: betternestedset-talk-bounces at rubyforge.org
> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Mikel
> Lindsaar
> Sent: 25 July 2007 00:20
> To: betternestedset-talk at rubyforge.org
> Subject: Re: [Betternestedset-talk] Display whole tree without 
> requestingdbfor each node
>
>
> If you have this as an ongoing requirement, a "simple" solution
might
> be storing the level in the model itself in an after save call back.
>
> It''s a bit of a hack, but you can only move the nodes through
update
> calls anyway... so it might work.  Then you have it automagically as 
> an instance method.
>
> Regards
>
> Mikel
>
> On 7/25/07, Tekin Suleyman <tekin at raid.nu> wrote:
>   
>> This is something I''ve wondered also as it more or less
cancels out
>> any speed gain from getting the full set in one query. Does 
>> betternestedset provide the hooks to cache the level? Alternatively, 
>> the parent_id could theoretically be used to calculate levels from a 
>> full set.
>>
>>
>>
>> -----Original Message-----
>> From: betternestedset-talk-bounces at rubyforge.org
>> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of
>> Jean-Christophe Michel
>> Sent: 23 July 2007 22:02
>> To: betternestedset-talk at rubyforge.org
>> Subject: Re: [Betternestedset-talk] Display whole tree without 
>> requesting dbfor each node
>>
>>
>> Hi,
>>
>> Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
>>     
>>> I?m wondering how I display the whole tree without having to
request
>>>       
>
>   
>>> the db each time I use @node.level.
>>>       
>> You have to cache the level in db, or simply compute it in code after
>> you read your tree part.
>>
>> Jean-Christophe Michel
>> --
>> symetrie.com
>>
>> Better Nested Set for rails:
>> http://opensource.symetrie.com/trac/better_nested_set
>>
>>
>> _______________________________________________
>> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
>> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>>
>> _______________________________________________
>> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
>> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>>
>>     
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
>   
_______________________________________________
Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
http://rubyforge.org/mailman/listinfo/betternestedset-talk

I wrote an iterator that iterates through the nested set in a
pre-order traversal, yielding each node, it''s level, and the relative
level of the next node. It can be used to print out ordered lists of
the set using only one db access. Here it is:

  # traverse {|current_node, level, relative_level_of_next| block }
  #
  # Iterates through the nodes in the nested set rooted at the
receiver, in a pre-order
  # traversal. For each node visited, it yields that node, its level,
and the relative level
  # of the next node to be visited. The values returned by successive
block executions are
  # accumulated (in an array by default) and returned at the end
  #
  # The receiver always has a level of 0.
  #
  # If relative_level_of_next is 1, the next node is guaranteed to be
the first (i.e. leftmost) child
  # of the current node
  # If it is 0, the next node is the next sibling of the the current node
  # Otherwise, relative level is a negative integer, indicating how
many levels above the current node
  # the next node is
  def traverse(accum = [])
    level = 0
    pre_order_array = full_set
    (pre_order_array.size - 1).times do |i|
      curr_node = pre_order_array[i]
      next_node = pre_order_array[i + 1]
      distance = next_node.lft - curr_node.lft
      relative_level_of_next = -1 * (distance - 2)
      accum << yield(curr_node, level, relative_level_of_next)
      level += relative_level_of_next
    end
    # Last node is handled differently to the rest: since there is no next node,
    # the relative_level_of_next is the number of levels back up to
the root level
    relative_level_of_next =  - 1 * (pre_order_array.first.rgt -
pre_order_array.last.rgt)
    accum << yield(pre_order_array.last, level, relative_level_of_next)
  end

Hope it helps.

Brian

On 8/6/07, Tekin Suleyman <tekin at raid.nu>
wrote:
>
> This isn''t actually as straight forward as it might seem. It
can''t be
> done in an after_save call back as you end up in an infinite loop. I
> thought you might be able to do it in a before_save, something like:
>
> before_save :cache_level
> alias_method :old_level, :level
> def level() self.level_cache; end
>
> private
> def cache_level
>   self.level_cache = self.old_level
> End
>
> And make sure you have a column in your table called level_cache. Now,
> when you call object.level, it won''t make a db call to calculate
the
> level, it will simply return the level_cache attribute.
>
> But I''m now not convinced it will exhibit correct behaviour - if
> old_cache is called before the object is updated, it will cache the
> current and not the new level, right?
>
> Any thoughts?
>
> Tekin
>
>
>
> -----Original Message-----
> From: betternestedset-talk-bounces at rubyforge.org
> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Jonas
> Arklint
> Sent: 06 August 2007 09:29
> To: betternestedset-talk at rubyforge.org
> Subject: Re: [Betternestedset-talk] Display whole tree without
> requestingdbfor each node
>
>
> I?m a littlebit confused. But how do i accomplish that? Storing level
> inside db that is.
>
> Tekin Suleyman skrev:
> > Why didn''t I think of that! I''ll give it a try.
> >
> > -----Original Message-----
> > From: betternestedset-talk-bounces at rubyforge.org
> > [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of
Mikel
>
> > Lindsaar
> > Sent: 25 July 2007 00:20
> > To: betternestedset-talk at rubyforge.org
> > Subject: Re: [Betternestedset-talk] Display whole tree without
> > requestingdbfor each node
> >
> >
> > If you have this as an ongoing requirement, a "simple"
solution might
> > be storing the level in the model itself in an after save call back.
> >
> > It''s a bit of a hack, but you can only move the nodes through
update
> > calls anyway... so it might work.  Then you have it automagically as
> > an instance method.
> >
> > Regards
> >
> > Mikel
> >
> > On 7/25/07, Tekin Suleyman <tekin at raid.nu> wrote:
> >
> >> This is something I''ve wondered also as it more or less
cancels out
> >> any speed gain from getting the full set in one query. Does
> >> betternestedset provide the hooks to cache the level?
Alternatively,
> >> the parent_id could theoretically be used to calculate levels from
a
> >> full set.
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: betternestedset-talk-bounces at rubyforge.org
> >> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf
Of
> >> Jean-Christophe Michel
> >> Sent: 23 July 2007 22:02
> >> To: betternestedset-talk at rubyforge.org
> >> Subject: Re: [Betternestedset-talk] Display whole tree without
> >> requesting dbfor each node
> >>
> >>
> >> Hi,
> >>
> >> Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
> >>
> >>> I?m wondering how I display the whole tree without having to
request
> >>>
> >
> >
> >>> the db each time I use @node.level.
> >>>
> >> You have to cache the level in db, or simply compute it in code
after
> >> you read your tree part.
> >>
> >> Jean-Christophe Michel
> >> --
> >> symetrie.com
> >>
> >> Better Nested Set for rails:
> >> http://opensource.symetrie.com/trac/better_nested_set
> >>
> >>
> >> _______________________________________________
> >> Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> >> http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >>
> >> _______________________________________________
> >> Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> >> http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >>
> >>
> > _______________________________________________
> > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >
> > _______________________________________________
> > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >
> >
>
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
> _______________________________________________
> Betternestedset-talk mailing list
> Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>

Cheers, that looks fantastic!
I''ll give it a shot and report back.

Tekin

-----Original Message-----
From: betternestedset-talk-bounces at rubyforge.org
[mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Brian
Sheehan
Sent: 10 August 2007 11:58
To: betternestedset-talk at rubyforge.org
Subject: Re: [Betternestedset-talk] Display whole tree
withoutrequestingdbfor each node


I wrote an iterator that iterates through the nested set in a pre-order
traversal, yielding each node, it''s level, and the relative level of
the
next node. It can be used to print out ordered lists of the set using
only one db access. Here it is:

  # traverse {|current_node, level, relative_level_of_next| block }
  #
  # Iterates through the nodes in the nested set rooted at the receiver,
in a pre-order
  # traversal. For each node visited, it yields that node, its level,
and the relative level
  # of the next node to be visited. The values returned by successive
block executions are
  # accumulated (in an array by default) and returned at the end
  #
  # The receiver always has a level of 0.
  #
  # If relative_level_of_next is 1, the next node is guaranteed to be
the first (i.e. leftmost) child
  # of the current node
  # If it is 0, the next node is the next sibling of the the current
node
  # Otherwise, relative level is a negative integer, indicating how many
levels above the current node
  # the next node is
  def traverse(accum = [])
    level = 0
    pre_order_array = full_set
    (pre_order_array.size - 1).times do |i|
      curr_node = pre_order_array[i]
      next_node = pre_order_array[i + 1]
      distance = next_node.lft - curr_node.lft
      relative_level_of_next = -1 * (distance - 2)
      accum << yield(curr_node, level, relative_level_of_next)
      level += relative_level_of_next
    end
    # Last node is handled differently to the rest: since there is no
next node,
    # the relative_level_of_next is the number of levels back up to the
root level
    relative_level_of_next =  - 1 * (pre_order_array.first.rgt -
pre_order_array.last.rgt)
    accum << yield(pre_order_array.last, level, relative_level_of_next)
  end

Hope it helps.

Brian

On 8/6/07, Tekin Suleyman <tekin at raid.nu>
wrote:
>
> This isn''t actually as straight forward as it might seem. It
can''t be
> done in an after_save call back as you end up in an infinite loop. I 
> thought you might be able to do it in a before_save, something like:
>
> before_save :cache_level
> alias_method :old_level, :level
> def level() self.level_cache; end
>
> private
> def cache_level
>   self.level_cache = self.old_level
> End
>
> And make sure you have a column in your table called level_cache. Now,
> when you call object.level, it won''t make a db call to calculate
the
> level, it will simply return the level_cache attribute.
>
> But I''m now not convinced it will exhibit correct behaviour - if 
> old_cache is called before the object is updated, it will cache the 
> current and not the new level, right?
>
> Any thoughts?
>
> Tekin
>
>
>
> -----Original Message-----
> From: betternestedset-talk-bounces at rubyforge.org
> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Jonas
> Arklint
> Sent: 06 August 2007 09:29
> To: betternestedset-talk at rubyforge.org
> Subject: Re: [Betternestedset-talk] Display whole tree without 
> requestingdbfor each node
>
>
> I?m a littlebit confused. But how do i accomplish that? Storing level 
> inside db that is.
>
> Tekin Suleyman skrev:
> > Why didn''t I think of that! I''ll give it a try.
> >
> > -----Original Message-----
> > From: betternestedset-talk-bounces at rubyforge.org
> > [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of 
> > Mikel
>
> > Lindsaar
> > Sent: 25 July 2007 00:20
> > To: betternestedset-talk at rubyforge.org
> > Subject: Re: [Betternestedset-talk] Display whole tree without 
> > requestingdbfor each node
> >
> >
> > If you have this as an ongoing requirement, a "simple"
solution
> > might be storing the level in the model itself in an after save call
> > back.
> >
> > It''s a bit of a hack, but you can only move the nodes through
update
> > calls anyway... so it might work.  Then you have it automagically as
> > an instance method.
> >
> > Regards
> >
> > Mikel
> >
> > On 7/25/07, Tekin Suleyman <tekin at raid.nu> wrote:
> >
> >> This is something I''ve wondered also as it more or less
cancels out
> >> any speed gain from getting the full set in one query. Does 
> >> betternestedset provide the hooks to cache the level? 
> >> Alternatively, the parent_id could theoretically be used to 
> >> calculate levels from a full set.
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: betternestedset-talk-bounces at rubyforge.org
> >> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf
Of
> >> Jean-Christophe Michel
> >> Sent: 23 July 2007 22:02
> >> To: betternestedset-talk at rubyforge.org
> >> Subject: Re: [Betternestedset-talk] Display whole tree without 
> >> requesting dbfor each node
> >>
> >>
> >> Hi,
> >>
> >> Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
> >>
> >>> I?m wondering how I display the whole tree without having to 
> >>> request
> >>>
> >
> >
> >>> the db each time I use @node.level.
> >>>
> >> You have to cache the level in db, or simply compute it in code 
> >> after you read your tree part.
> >>
> >> Jean-Christophe Michel
> >> --
> >> symetrie.com
> >>
> >> Better Nested Set for rails: 
> >> http://opensource.symetrie.com/trac/better_nested_set
> >>
> >>
> >> _______________________________________________
> >> Betternestedset-talk mailing list 
> >> Betternestedset-talk at rubyforge.org
> >> http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >>
> >> _______________________________________________
> >> Betternestedset-talk mailing list 
> >> Betternestedset-talk at rubyforge.org
> >> http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >>
> >>
> > _______________________________________________
> > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >
> > _______________________________________________
> > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >
> >
>
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
_______________________________________________
Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
http://rubyforge.org/mailman/listinfo/betternestedset-talk

Works a treat!

I modified it slightly as I have several roots and want the whole thing
traversed: I made it a class method and instead of full_set it calls
complete_set.
Thanks Brian, very handy indeed.

Tekin

-----Original Message-----
From: betternestedset-talk-bounces at rubyforge.org
[mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Brian
Sheehan
Sent: 10 August 2007 11:58
To: betternestedset-talk at rubyforge.org
Subject: Re: [Betternestedset-talk] Display whole tree
withoutrequestingdbfor each node


I wrote an iterator that iterates through the nested set in a pre-order
traversal, yielding each node, it''s level, and the relative level of
the
next node. It can be used to print out ordered lists of the set using
only one db access. Here it is:

  # traverse {|current_node, level, relative_level_of_next| block }
  #
  # Iterates through the nodes in the nested set rooted at the receiver,
in a pre-order
  # traversal. For each node visited, it yields that node, its level,
and the relative level
  # of the next node to be visited. The values returned by successive
block executions are
  # accumulated (in an array by default) and returned at the end
  #
  # The receiver always has a level of 0.
  #
  # If relative_level_of_next is 1, the next node is guaranteed to be
the first (i.e. leftmost) child
  # of the current node
  # If it is 0, the next node is the next sibling of the the current
node
  # Otherwise, relative level is a negative integer, indicating how many
levels above the current node
  # the next node is
  def traverse(accum = [])
    level = 0
    pre_order_array = full_set
    (pre_order_array.size - 1).times do |i|
      curr_node = pre_order_array[i]
      next_node = pre_order_array[i + 1]
      distance = next_node.lft - curr_node.lft
      relative_level_of_next = -1 * (distance - 2)
      accum << yield(curr_node, level, relative_level_of_next)
      level += relative_level_of_next
    end
    # Last node is handled differently to the rest: since there is no
next node,
    # the relative_level_of_next is the number of levels back up to the
root level
    relative_level_of_next =  - 1 * (pre_order_array.first.rgt -
pre_order_array.last.rgt)
    accum << yield(pre_order_array.last, level, relative_level_of_next)
  end

Hope it helps.

Brian

On 8/6/07, Tekin Suleyman <tekin at raid.nu>
wrote:
>
> This isn''t actually as straight forward as it might seem. It
can''t be
> done in an after_save call back as you end up in an infinite loop. I 
> thought you might be able to do it in a before_save, something like:
>
> before_save :cache_level
> alias_method :old_level, :level
> def level() self.level_cache; end
>
> private
> def cache_level
>   self.level_cache = self.old_level
> End
>
> And make sure you have a column in your table called level_cache. Now,
> when you call object.level, it won''t make a db call to calculate
the
> level, it will simply return the level_cache attribute.
>
> But I''m now not convinced it will exhibit correct behaviour - if 
> old_cache is called before the object is updated, it will cache the 
> current and not the new level, right?
>
> Any thoughts?
>
> Tekin
>
>
>
> -----Original Message-----
> From: betternestedset-talk-bounces at rubyforge.org
> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Jonas
> Arklint
> Sent: 06 August 2007 09:29
> To: betternestedset-talk at rubyforge.org
> Subject: Re: [Betternestedset-talk] Display whole tree without 
> requestingdbfor each node
>
>
> I?m a littlebit confused. But how do i accomplish that? Storing level 
> inside db that is.
>
> Tekin Suleyman skrev:
> > Why didn''t I think of that! I''ll give it a try.
> >
> > -----Original Message-----
> > From: betternestedset-talk-bounces at rubyforge.org
> > [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of 
> > Mikel
>
> > Lindsaar
> > Sent: 25 July 2007 00:20
> > To: betternestedset-talk at rubyforge.org
> > Subject: Re: [Betternestedset-talk] Display whole tree without 
> > requestingdbfor each node
> >
> >
> > If you have this as an ongoing requirement, a "simple"
solution
> > might be storing the level in the model itself in an after save call
> > back.
> >
> > It''s a bit of a hack, but you can only move the nodes through
update
> > calls anyway... so it might work.  Then you have it automagically as
> > an instance method.
> >
> > Regards
> >
> > Mikel
> >
> > On 7/25/07, Tekin Suleyman <tekin at raid.nu> wrote:
> >
> >> This is something I''ve wondered also as it more or less
cancels out
> >> any speed gain from getting the full set in one query. Does 
> >> betternestedset provide the hooks to cache the level? 
> >> Alternatively, the parent_id could theoretically be used to 
> >> calculate levels from a full set.
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: betternestedset-talk-bounces at rubyforge.org
> >> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf
Of
> >> Jean-Christophe Michel
> >> Sent: 23 July 2007 22:02
> >> To: betternestedset-talk at rubyforge.org
> >> Subject: Re: [Betternestedset-talk] Display whole tree without 
> >> requesting dbfor each node
> >>
> >>
> >> Hi,
> >>
> >> Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
> >>
> >>> I?m wondering how I display the whole tree without having to 
> >>> request
> >>>
> >
> >
> >>> the db each time I use @node.level.
> >>>
> >> You have to cache the level in db, or simply compute it in code 
> >> after you read your tree part.
> >>
> >> Jean-Christophe Michel
> >> --
> >> symetrie.com
> >>
> >> Better Nested Set for rails: 
> >> http://opensource.symetrie.com/trac/better_nested_set
> >>
> >>
> >> _______________________________________________
> >> Betternestedset-talk mailing list 
> >> Betternestedset-talk at rubyforge.org
> >> http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >>
> >> _______________________________________________
> >> Betternestedset-talk mailing list 
> >> Betternestedset-talk at rubyforge.org
> >> http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >>
> >>
> > _______________________________________________
> > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >
> > _______________________________________________
> > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >
> >
>
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
_______________________________________________
Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
http://rubyforge.org/mailman/listinfo/betternestedset-talk
-------------- next part --------------
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Glad to hear it. I haven''t done much testing on that method, so post
back if you run into any issues.

thanks for the patch,

Brian

On 8/10/07, Tekin Suleyman <tekin at raid.nu>
wrote:
> Works a treat!
>
> I modified it slightly as I have several roots and want the whole thing
> traversed: I made it a class method and instead of full_set it calls
> complete_set.
> Thanks Brian, very handy indeed.
>
> Tekin
>
> -----Original Message-----
> From: betternestedset-talk-bounces at rubyforge.org
> [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of Brian
> Sheehan
> Sent: 10 August 2007 11:58
> To: betternestedset-talk at rubyforge.org
> Subject: Re: [Betternestedset-talk] Display whole tree
> withoutrequestingdbfor each node
>
>
> I wrote an iterator that iterates through the nested set in a pre-order
> traversal, yielding each node, it''s level, and the relative level
of the
> next node. It can be used to print out ordered lists of the set using
> only one db access. Here it is:
>
>   # traverse {|current_node, level, relative_level_of_next| block }
>   #
>   # Iterates through the nodes in the nested set rooted at the receiver,
> in a pre-order
>   # traversal. For each node visited, it yields that node, its level,
> and the relative level
>   # of the next node to be visited. The values returned by successive
> block executions are
>   # accumulated (in an array by default) and returned at the end
>   #
>   # The receiver always has a level of 0.
>   #
>   # If relative_level_of_next is 1, the next node is guaranteed to be
> the first (i.e. leftmost) child
>   # of the current node
>   # If it is 0, the next node is the next sibling of the the current
> node
>   # Otherwise, relative level is a negative integer, indicating how many
> levels above the current node
>   # the next node is
>   def traverse(accum = [])
>     level = 0
>     pre_order_array = full_set
>     (pre_order_array.size - 1).times do |i|
>       curr_node = pre_order_array[i]
>       next_node = pre_order_array[i + 1]
>       distance = next_node.lft - curr_node.lft
>       relative_level_of_next = -1 * (distance - 2)
>       accum << yield(curr_node, level, relative_level_of_next)
>       level += relative_level_of_next
>     end
>     # Last node is handled differently to the rest: since there is no
> next node,
>     # the relative_level_of_next is the number of levels back up to the
> root level
>     relative_level_of_next =  - 1 * (pre_order_array.first.rgt -
> pre_order_array.last.rgt)
>     accum << yield(pre_order_array.last, level,
relative_level_of_next)
>   end
>
> Hope it helps.
>
> Brian
>
> On 8/6/07, Tekin Suleyman <tekin at raid.nu> wrote:
> >
> > This isn''t actually as straight forward as it might seem. It
can''t be
> > done in an after_save call back as you end up in an infinite loop. I
> > thought you might be able to do it in a before_save, something like:
> >
> > before_save :cache_level
> > alias_method :old_level, :level
> > def level() self.level_cache; end
> >
> > private
> > def cache_level
> >   self.level_cache = self.old_level
> > End
> >
> > And make sure you have a column in your table called level_cache. Now,
>
> > when you call object.level, it won''t make a db call to
calculate the
> > level, it will simply return the level_cache attribute.
> >
> > But I''m now not convinced it will exhibit correct behaviour -
if
> > old_cache is called before the object is updated, it will cache the
> > current and not the new level, right?
> >
> > Any thoughts?
> >
> > Tekin
> >
> >
> >
> > -----Original Message-----
> > From: betternestedset-talk-bounces at rubyforge.org
> > [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf Of
Jonas
>
> > Arklint
> > Sent: 06 August 2007 09:29
> > To: betternestedset-talk at rubyforge.org
> > Subject: Re: [Betternestedset-talk] Display whole tree without
> > requestingdbfor each node
> >
> >
> > I?m a littlebit confused. But how do i accomplish that? Storing level
> > inside db that is.
> >
> > Tekin Suleyman skrev:
> > > Why didn''t I think of that! I''ll give it a try.
> > >
> > > -----Original Message-----
> > > From: betternestedset-talk-bounces at rubyforge.org
> > > [mailto:betternestedset-talk-bounces at rubyforge.org] On Behalf
Of
> > > Mikel
> >
> > > Lindsaar
> > > Sent: 25 July 2007 00:20
> > > To: betternestedset-talk at rubyforge.org
> > > Subject: Re: [Betternestedset-talk] Display whole tree without
> > > requestingdbfor each node
> > >
> > >
> > > If you have this as an ongoing requirement, a "simple"
solution
> > > might be storing the level in the model itself in an after save
call
>
> > > back.
> > >
> > > It''s a bit of a hack, but you can only move the nodes
through update
>
> > > calls anyway... so it might work.  Then you have it automagically
as
>
> > > an instance method.
> > >
> > > Regards
> > >
> > > Mikel
> > >
> > > On 7/25/07, Tekin Suleyman <tekin at raid.nu> wrote:
> > >
> > >> This is something I''ve wondered also as it more or
less cancels out
>
> > >> any speed gain from getting the full set in one query. Does
> > >> betternestedset provide the hooks to cache the level?
> > >> Alternatively, the parent_id could theoretically be used to
> > >> calculate levels from a full set.
> > >>
> > >>
> > >>
> > >> -----Original Message-----
> > >> From: betternestedset-talk-bounces at rubyforge.org
> > >> [mailto:betternestedset-talk-bounces at rubyforge.org] On
Behalf Of
> > >> Jean-Christophe Michel
> > >> Sent: 23 July 2007 22:02
> > >> To: betternestedset-talk at rubyforge.org
> > >> Subject: Re: [Betternestedset-talk] Display whole tree
without
> > >> requesting dbfor each node
> > >>
> > >>
> > >> Hi,
> > >>
> > >> Le 23 juil. 07 ? 17:37, Jonas Arklint a ?crit :
> > >>
> > >>> I?m wondering how I display the whole tree without having
to
> > >>> request
> > >>>
> > >
> > >
> > >>> the db each time I use @node.level.
> > >>>
> > >> You have to cache the level in db, or simply compute it in
code
> > >> after you read your tree part.
> > >>
> > >> Jean-Christophe Michel
> > >> --
> > >> symetrie.com
> > >>
> > >> Better Nested Set for rails:
> > >> http://opensource.symetrie.com/trac/better_nested_set
> > >>
> > >>
> > >> _______________________________________________
> > >> Betternestedset-talk mailing list
> > >> Betternestedset-talk at rubyforge.org
> > >> http://rubyforge.org/mailman/listinfo/betternestedset-talk
> > >>
> > >> _______________________________________________
> > >> Betternestedset-talk mailing list
> > >> Betternestedset-talk at rubyforge.org
> > >> http://rubyforge.org/mailman/listinfo/betternestedset-talk
> > >>
> > >>
> > > _______________________________________________
> > > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> > >
> > > _______________________________________________
> > > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> > >
> > >
> >
> > _______________________________________________
> > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >
> > _______________________________________________
> > Betternestedset-talk mailing list Betternestedset-talk at
rubyforge.org
> > http://rubyforge.org/mailman/listinfo/betternestedset-talk
> >
> _______________________________________________
> Betternestedset-talk mailing list Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
> _______________________________________________
> Betternestedset-talk mailing list
> Betternestedset-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/betternestedset-talk
>
>
>