Merge pull request #13938 from marcandre/sized_enumerator

Sized enumerator

5 files changed, 48 insertions, 8 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index d14b5b27f8..f1d51b9de1 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   `find_in_batches`, `find_each`, `Result#each` and `Enumerable#index_by` now
+    return an `Enumerator` that can calculate its size.
+
+    See also #13938.
+
+    *Marc-André Lafortune*
+
 *   Make sure transaction state gets reset after a commit operation on the record.
 
     If a new transaction was open inside a callback, the record was loosing track
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index 666cef80a9..29fc150b3d 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -52,7 +52,9 @@ module ActiveRecord
           records.each { |record| yield record }
         end
       else
-        enum_for :find_each, options
+        enum_for :find_each, options do
+          options[:start] ? where(table[primary_key].gteq(options[:start])).size : size
+        end
       end
     end
 
@@ -96,17 +98,22 @@ module ActiveRecord
     # the batch sizes.
     def find_in_batches(options = {})
       options.assert_valid_keys(:start, :batch_size)
-      return to_enum(:find_in_batches, options) unless block_given?
 
       relation = self
+      start = options[:start]
+      batch_size = options[:batch_size] || 1000
+
+      unless block_given?
+        return to_enum(:find_in_batches, options) do
+          total = start ? where(table[primary_key].gteq(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
 
-      start = options[:start]
-      batch_size = options[:batch_size] || 1000
-
       relation = relation.reorder(batch_order).limit(batch_size)
       records = start ? relation.where(table[primary_key].gteq(start)).to_a : relation.to_a
 
diff --git a/activerecord/lib/active_record/result.rb b/activerecord/lib/active_record/result.rb
index 469451e2f4..228b2aa60f 100644
--- a/activerecord/lib/active_record/result.rb
+++ b/activerecord/lib/active_record/result.rb
@@ -54,7 +54,7 @@ module ActiveRecord
       if block_given?
         hash_rows.each { |row| yield row }
       else
-        hash_rows.to_enum
+        hash_rows.to_enum { @rows.size }
       end
     end
 
diff --git a/activerecord/test/cases/batches_test.rb b/activerecord/test/cases/batches_test.rb
index 8216d74cb3..c12fa03015 100644
--- a/activerecord/test/cases/batches_test.rb
+++ b/activerecord/test/cases/batches_test.rb
@@ -35,6 +35,14 @@ class EachTest < ActiveRecord::TestCase
     end
   end
 
+  if Enumerator.method_defined? :size
+    def test_each_should_return_a_sized_enumerator
+      assert_equal 11, Post.find_each(:batch_size => 1).size
+      assert_equal 5, Post.find_each(:batch_size => 2, :start => 7).size
+      assert_equal 11, Post.find_each(:batch_size => 10_000).size
+    end
+  end
+
   def test_each_enumerator_should_execute_one_query_per_batch
     assert_queries(@total + 1) do
       Post.find_each(:batch_size => 1).with_index do |post, index|
@@ -191,4 +199,14 @@ class EachTest < ActiveRecord::TestCase
       end
     end
   end
+
+  if Enumerator.method_defined? :size
+    def test_find_in_batches_should_return_a_sized_enumerator
+      assert_equal 11, Post.find_in_batches(:batch_size => 1).size
+      assert_equal 6, Post.find_in_batches(:batch_size => 2).size
+      assert_equal 4, Post.find_in_batches(:batch_size => 2, :start => 4).size
+      assert_equal 4, Post.find_in_batches(:batch_size => 3).size
+      assert_equal 1, Post.find_in_batches(:batch_size => 10_000).size
+    end
+  end
 end
diff --git a/activerecord/test/cases/result_test.rb b/activerecord/test/cases/result_test.rb
index b6c583dbf5..2131b32a0c 100644
--- a/activerecord/test/cases/result_test.rb
+++ b/activerecord/test/cases/result_test.rb
@@ -5,14 +5,16 @@ module ActiveRecord
     def result
       Result.new(['col_1', 'col_2'], [
         ['row 1 col 1', 'row 1 col 2'],
-        ['row 2 col 1', 'row 2 col 2']
+        ['row 2 col 1', 'row 2 col 2'],
+        ['row 3 col 1', 'row 3 col 2'],
       ])
     end
 
     def test_to_hash_returns_row_hashes
       assert_equal [
         {'col_1' => 'row 1 col 1', 'col_2' => 'row 1 col 2'},
-        {'col_1' => 'row 2 col 1', 'col_2' => 'row 2 col 2'}
+        {'col_1' => 'row 2 col 1', 'col_2' => 'row 2 col 2'},
+        {'col_1' => 'row 3 col 1', 'col_2' => 'row 3 col 2'},
       ], result.to_hash
     end
 
@@ -28,5 +30,11 @@ module ActiveRecord
         assert_kind_of Integer, index
       end
     end
+
+    if Enumerator.method_defined? :size
+      def test_each_without_block_returns_a_sized_enumerator
+        assert_equal 3, result.each.size
+      end
+    end
   end
 end