diff options
Diffstat (limited to 'activerecord/lib/active_record/relation/batches.rb')
| -rw-r--r-- | activerecord/lib/active_record/relation/batches.rb | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb index 15f838a5ab..fb4388d4b2 100644 --- a/activerecord/lib/active_record/relation/batches.rb +++ b/activerecord/lib/active_record/relation/batches.rb @@ -2,20 +2,26 @@ require 'active_support/core_ext/object/blank' module ActiveRecord module Batches - # Yields each record that was found by the find +options+. The find is - # performed by find_in_batches with a batch size of 1000 (or as + # Looping through a collection of records from the database + # (using the +all+ method, for example) is very inefficient + # since it will try to instantiate all the objects at once. + # + # In that case, batch processing methods allow you to work + # with the records in batches, thereby greatly reducing memory consumption. + # + # The <tt>find_each</tt> method uses <tt>find_in_batches</tt> with a batch size of 1000 (or as # specified by the <tt>:batch_size</tt> option). # - # Example: + # Person.all.find_each do |person| + # person.do_awesome_stuff + # end # # Person.where("age > 21").find_each do |person| # person.party_all_night! # end # - # Note: This method is only intended to use for batch processing of - # large amounts of records that wouldn't fit in memory all at once. If - # you just need to loop over less than 1000 records, it's probably - # better just to use the regular find methods. + # You can also pass the <tt>:start</tt> option to specify + # an offset to control the starting point. def find_each(options = {}) find_in_batches(options) do |records| records.each { |record| yield record } @@ -39,12 +45,15 @@ module ActiveRecord # primary keys. You can't set the limit either, that's used to control # the batch sizes. # - # Example: - # # Person.where("age > 21").find_in_batches do |group| # sleep(50) # Make sure it doesn't get too crowded in there! # group.each { |person| person.party_all_night! } # end + # + # # Let's process the next 2000 records + # Person.all.find_in_batches(start: 2000, batch_size: 2000) do |group| + # group.each { |person| person.party_all_night! } + # end def find_in_batches(options = {}) options.assert_valid_keys(:start, :batch_size) |