Rails - Sep 2005 - Which is better : array#select or activerecord#find

Hello all,

I have a table with 8000 rows.  Certain selections ( @item_status #find(:all,
:conditions...) ) return 550 rows.
I have to iterate a separate list @items, matching @items[].name to
@item_status[].name
Hit rate on the match will be anywhere from 50%-100%.  @items is an
array of WIN32OLE items.

So the question is this :
Is it better to: 

A) Retrieve entire data result ( @item_status#find(:all,
:conditions=>"foreign_key = ''blah''") ) and then
use @item_status#select
{|i| i.name =~ @item.name}

B) Retrieve only (possibly nil) exact item ( @item_status#find(:all,
:conditions=>"foreign_key = ''blah'' AND name =
''#{@item.name}''")

C) Quit being nitpicky and don''t worry about an N^2 process across the
LAN wire against 500 items ?

D) Use the RUBY WAY and do this with some kind of tricky hash magic or
something ?

Thanks for the advice!

Peter J. Fitzgibbons
Applications Manager
Lakewood Homes - "The American Dream Builder"(r)
Peter.Fitzgibbons-STCS76aLmhk1y/cD6r8xzl6hYfS7NtTn@public.gmane.org
(847) 884-8800 




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On Monday 12 September 2005 22:30, Peter Fitzgibbons
wrote:
> Hello all,
>
> I have a table with 8000 rows.  Certain selections ( @item_status >
#find(:all, :conditions...) ) return 550 rows.
> I have to iterate a separate list @items, matching @items[].name to
> @item_status[].name
> Hit rate on the match will be anywhere from 50%-100%.  @items is an
> array of WIN32OLE items.
>
> So the question is this :
> Is it better to:
The best you can do is measure the different approaches in your specific 
context.
>
> A) Retrieve entire data result ( @item_status#find(:all,
>
> :conditions=>"foreign_key = ''blah''") ) and
then use
> : @item_status#select
> {|i| i.name =~ @item.name}
No, see below.
> B) Retrieve only (possibly nil) exact item ( @item_status#find(:all,
> :conditions=>"foreign_key = ''blah'' AND name =
''#{@item.name}''")
Going to the DB for each item individually? Sounds pretty bad.
> C) Quit being nitpicky and don''t worry about an N^2 process across
> the LAN wire against 500 items ?
Keep both lists sorted or sort them on the spot. Then matching itself is 
linear.

Michael

-- 
Michael Schuerig                  Failures to use one''s frontal lobes
mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org        can result in the
loss of them.
http://www.schuerig.de/michael/   --William H. Calvin