aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/relation/batches.rb
blob: f7b2167ae8c5ee1f0490836fa39da426c9519736 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
module ActiveRecord
  module Batches
    # 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 #find_each method uses #find_in_batches with a batch size of 1000 (or as
    # specified by the +:batch_size+ option).
    #
    #   Person.find_each do |person|
    #     person.do_awesome_stuff
    #   end
    #
    #   Person.where("age > 21").find_each do |person|
    #     person.party_all_night!
    #   end
    #
    # If you do not provide a block to #find_each, it will return an Enumerator
    # for chaining with other methods:
    #
    #   Person.find_each.with_index do |person, index|
    #     person.award_trophy(index + 1)
    #   end
    #
    # ==== Options
    # * <tt>:batch_size</tt> - Specifies the size of the batch. Default to 1000.
    # * <tt>:start</tt> - Specifies the primary key value to start from.
    # This is especially useful if you want multiple workers dealing with
    # the same processing queue. You can make worker 1 handle all the records
    # between id 0 and 10,000 and worker 2 handle from 10,000 and beyond
    # (by setting the +:start+ option on that worker).
    #
    #   # Let's process for a batch of 2000 records, skipping the first 2000 rows
    #   Person.find_each(start: 2000, batch_size: 2000) do |person|
    #     person.party_all_night!
    #   end
    #
    # NOTE: It's not possible to set the order. That is automatically set to
    # ascending on the primary key ("id ASC") to make the batch ordering
    # work. This also means that this method only works when the primary key is
    # orderable (e.g. an integer or string).
    #
    # NOTE: You can't set the limit either, that's used to control
    # the batch sizes.
    def find_each(options = {})
      if block_given?
        find_in_batches(options) do |records|
          records.each { |record| yield record }
        end
      else
        enum_for :find_each, options do
          # FIXME: Remove this when type casting is removed from Arel
          # (Rails 5.1). We can pass start directly instead.
          if options[:start]
            quoted_start = Arel::Nodes::Quoted.new(options[:start])
          end
          options[:start] ? where(table[primary_key].gteq(quoted_start)).size : size
        end
      end
    end

    # Yields each batch of records that was found by the find +options+ as
    # an array.
    #
    #   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
    #
    # If you do not provide a block to #find_in_batches, it will return an Enumerator
    # for chaining with other methods:
    #
    #   Person.find_in_batches.with_index do |group, batch|
    #     puts "Processing group ##{batch}"
    #     group.each(&:recover_from_last_night!)
    #   end
    #
    # To be yielded each record one by one, use #find_each instead.
    #
    # ==== Options
    # * <tt>:batch_size</tt> - Specifies the size of the batch. Default to 1000.
    # * <tt>:start</tt> - Specifies the primary key value to start from.
    # This is especially useful if you want multiple workers dealing with
    # the same processing queue. You can make worker 1 handle all the records
    # between id 0 and 10,000 and worker 2 handle from 10,000 and beyond
    # (by setting the +:start+ option on that worker).
    #
    #   # Let's process the next 2000 records
    #   Person.find_in_batches(start: 2000, batch_size: 2000) do |group|
    #     group.each { |person| person.party_all_night! }
    #   end
    #
    # NOTE: It's not possible to set the order. That is automatically set to
    # ascending on the primary key ("id ASC") to make the batch ordering
    # work. This also means that this method only works when the primary key is
    # orderable (e.g. an integer or string).
    #
    # NOTE: You can't set the limit either, that's used to control
    # the batch sizes.
    def find_in_batches(options = {})
      options.assert_valid_keys(:start, :batch_size)

      relation = self
      start = options[:start]
      batch_size = options[:batch_size] || 1000

      if start
        # FIXME: Remove this when type casting is removed from Arel
        # (Rails 5.1). We can pass start directly instead.
        quoted_start = Arel::Nodes::Quoted.new(start)
      end

      unless block_given?
        return to_enum(:find_in_batches, options) do
          total = start ? where(table[primary_key].gteq(quoted_start)).size : size
          (total - 1).div(batch_size) + 1
        end
      end

      if logger && (arel.orders.present? || arel.taken.present?)
        logger.warn("Scoped order and limit are ignored, it's forced to be batch order and batch size")
      end

      relation = relation.reorder(batch_order).limit(batch_size)
      records = start ? relation.where(table[primary_key].gteq(quoted_start)).to_a : relation.to_a

      while records.any?
        records_size = records.size
        primary_key_offset = records.last.id
        raise "Primary key not included in the custom select clause" unless primary_key_offset

        yield records

        break if records_size < batch_size

        # FIXME: Remove this when type casting is removed from Arel
        # (Rails 5.1). We can pass the offset directly instead.
        quoted_offset = Arel::Nodes::Quoted.new(primary_key_offset)

        records = relation.where(table[primary_key].gt(quoted_offset)).to_a
      end
    end

    private

    def batch_order
      "#{quoted_table_name}.#{quoted_primary_key} ASC"
    end
  end
end