Kevin Scaldeferri
2009-Feb-23 20:28 UTC
How to get cursor / lazy semantics from find(:all)
I''m trying to figure out it there''s some alternative to
find(:all)
that can avoid instantiating every object at once, when I know that
I''m just going to iterate over the collection and throw it away. E.g.
def batch_process
User.find(:all).each do |user|
batch_process_one_user(user)
end
end
Unfortunately, this may instantiate millions of User objects and use
up GB of memory, which is not acceptable. I''ve been digging through
docs and code trying to figure out how I can do this within Rails,
rather than having to go down to the raw DB connection and build from
there, or pushing everything into a stored procedure.
Thanks,
-kevin
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Frederick Cheung
2009-Feb-23 20:37 UTC
Re: How to get cursor / lazy semantics from find(:all)
On Feb 23, 8:28 pm, Kevin Scaldeferri <kevin+goo...-JJkA4VpjLwo0zfciT3NkkQ@public.gmane.org> wrote:> I''m trying to figure out it there''s some alternative to find(:all) > that can avoid instantiating every object at once, when I know that > I''m just going to iterate over the collection and throw it away. E.g. >http://github.com/rails/rails/commit/d13623ca46c82120c398f4634e206422fc3ad7ea ? Fred> def batch_process > User.find(:all).each do |user| > batch_process_one_user(user) > end > end > > Unfortunately, this may instantiate millions of User objects and use > up GB of memory, which is not acceptable. I''ve been digging through > docs and code trying to figure out how I can do this within Rails, > rather than having to go down to the raw DB connection and build from > there, or pushing everything into a stored procedure. > > Thanks, > > -kevin--~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Kevin Scaldeferri
2009-Feb-23 22:19 UTC
Re: How to get cursor / lazy semantics from find(:all)
Thanks! That''s close enough and easy to backport. In principle, a solution that did O(1) queries, rather than O(N) would be nice, but the reduction in memory use at least gets me back to something tolerable. -kevin On Feb 23, 2009, at 12:37 PM, Frederick Cheung wrote:> > > > On Feb 23, 8:28 pm, Kevin Scaldeferri <kevin+goo...-JJkA4VpjLwo0zfciT3NkkQ@public.gmane.org> > wrote: >> I''m trying to figure out it there''s some alternative to find(:all) >> that can avoid instantiating every object at once, when I know that >> I''m just going to iterate over the collection and throw it away. >> E.g. >> > > http://github.com/rails/rails/commit/d13623ca46c82120c398f4634e206422fc3ad7ea > ? > > Fred >> def batch_process >> User.find(:all).each do |user| >> batch_process_one_user(user) >> end >> end >> >> Unfortunately, this may instantiate millions of User objects and use >> up GB of memory, which is not acceptable. I''ve been digging through >> docs and code trying to figure out how I can do this within Rails, >> rather than having to go down to the raw DB connection and build from >> there, or pushing everything into a stored procedure. >> >> Thanks, >> >> -kevin > >--~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---