From dc3cc6c608b93209b23bbebd2ade04835abd6f6c Mon Sep 17 00:00:00 2001
From: Pratik Naik <pratiknaik@gmail.com>
Date: Fri, 12 Feb 2010 16:53:51 +0000
Subject: Move batch finders to Relation

---
 activerecord/lib/active_record/relation/batches.rb | 78 ++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 activerecord/lib/active_record/relation/batches.rb

(limited to 'activerecord/lib/active_record/relation')

diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
new file mode 100644
index 0000000000..4a260d4caa
--- /dev/null
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -0,0 +1,78 @@
+module ActiveRecord
+  module Batches # :nodoc:
+    # 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
+    # specified by the <tt>:batch_size</tt> option).
+    #
+    # Example:
+    #
+    #   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.
+    def find_each(options = {})
+      find_in_batches(options) do |records|
+        records.each { |record| yield record }
+      end
+
+      self
+    end
+
+    # Yields each batch of records that was found by the find +options+ as
+    # an array. The size of each batch is set by the <tt>:batch_size</tt>
+    # option; the default is 1000.
+    #
+    # You can control the starting point for the batch processing by
+    # supplying the <tt>:start</tt> option. 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 <tt>:start</tt>
+    # option on that worker).
+    #
+    # 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 mean that this method only works with integer-based
+    # primary keys. You can't set the limit either, that's used to control
+    # the 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
+    def find_in_batches(options = {})
+      relation = self
+
+      if (finder_options = options.except(:start, :batch_size)).present?
+        raise "You can't specify an order, it's forced to be #{batch_order}" if options[:order].present?
+        raise "You can't specify a limit, it's forced to be the batch_size"  if options[:limit].present?
+
+        relation = apply_finder_options(finder_options)
+      end
+
+      start = options.delete(:start).to_i
+      batch_size = options.delete(:batch_size) || 1000
+
+      relation = relation.except(:order).order(batch_order).limit(batch_size)
+      records = relation.where(primary_key.gteq(start)).all
+
+      while records.any?
+        yield records
+
+        break if records.size < batch_size
+        records = relation.where(primary_key.gt(records.last.id)).all
+      end
+    end
+
+    private
+
+    def batch_order
+      "#{@klass.table_name}.#{@klass.primary_key} ASC"
+    end
+  end
+end
\ No newline at end of file
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