The other issue I've had with eager loading is when I want to do a
rake task to compute on tens of thousands or hundreds of thousands of
records.
I could easily blow my memory by loading them all at once. Instead
it's better to eager-load in 'batches' or 'pages.'
I've dealt with this by monkey-patching in the following:
module DataMapper
class Collection
def batch_each(size=100,&block)
start = 0
loop do
n = all(:offset=>start,:limit=>size).each{|x| block.call
(x)}.size
break if n < size # feels icky, why can't ruby have a run-
at-least-once do..while?
start += size
end
end
end
end
It's really pleasing to me because the all(:offset=>,:limit=>) scopes
off of the prior query, and the batch_each is as easy to write as
each.
At some point I might get around to writing an each_with_index
version, but that would require me writing my own
"each_with_offsetted_index" for enumerable that takes in a starting
value.
-Gary
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