Schema dumper now records scale 0 decimal columns as decimal not integer.

The schema dumper would dump out any decimal or numeric column that had a zero
scale as an integer column. This will cause problems for very large precision
columns on some DBMSs, particularly PostgreSQL. It also looks strange to see
your column change type after moving through schema.rb.
Signed-off-by: NMichael Koziarski <michael@koziarski.com>
[#2741 state:committed]

activerecord/lib/active_record/schema_dumper.rb

@@ -99,8 +99,15 @@ def table(table, stream)
             next if column.name == pk
             spec = {}
             spec[:name]      = column.name.inspect
-            spec[:type]      = column.type.to_s
-            spec[:limit]     = column.limit.inspect if column.limit != @types[column.type][:limit] && column.type != :decimal
+            
+            # AR has an optimisation which handles zero-scale decimals as integers.  This
+            # code ensures that the dumper still dumps the column as a decimal.
+            spec[:type]      = if column.type == :integer && [/^numeric/, /^decimal/].any? { |e| e.match(column.sql_type) }
+                                 'decimal'
+                               else
+                                 column.type.to_s
+                               end
+            spec[:limit]     = column.limit.inspect if column.limit != @types[column.type][:limit] && spec[:type] != 'decimal'
             spec[:precision] = column.precision.inspect if !column.precision.nil?
             spec[:scale]     = column.scale.inspect if !column.scale.nil?
             spec[:null]      = 'false' if !column.null

activerecord/test/cases/schema_dumper_test.rb

@@ -190,4 +190,9 @@ def test_schema_dump_includes_decimal_options
     output = stream.string
     assert_match %r{:precision => 3,[[:space:]]+:scale => 2,[[:space:]]+:default => 2.78}, output
   end
+
+  def test_schema_dump_keeps_large_precision_integer_columns_as_decimal
+    output = standard_dump
+    assert_match %r{t.decimal\s+"atoms_in_universe",\s+:precision => 55,\s+:scale => 0}, output
+  end
 end

activerecord/test/schema/schema.rb

@@ -273,6 +273,7 @@ def create_table(*args, &block)
     t.decimal :my_house_population, :precision => 2, :scale => 0
     t.decimal :decimal_number_with_default, :precision => 3, :scale => 2, :default => 2.78
     t.float   :temperature
+    t.decimal :atoms_in_universe, :precision => 55, :scale => 0
   end
 
   create_table :orders, :force => true do |t|