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: Michael Koziarski <michael@koziarski.com>
[#2741 state:committed]

3 files changed, 15 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/schema_dumper.rb b/activerecord/lib/active_record/schema_dumper.rb
index de530a3456..2d90ef35aa 100644
--- a/activerecord/lib/active_record/schema_dumper.rb
+++ b/activerecord/lib/active_record/schema_dumper.rb
@@ -99,8 +99,15 @@ HEADER
             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
diff --git a/activerecord/test/cases/schema_dumper_test.rb b/activerecord/test/cases/schema_dumper_test.rb
index f9ad7f3ba3..4f02be3c06 100644
--- a/activerecord/test/cases/schema_dumper_test.rb
+++ b/activerecord/test/cases/schema_dumper_test.rb
@@ -190,4 +190,9 @@ class SchemaDumperTest < ActiveRecord::TestCase
     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
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 6e8813d8ab..b2aaccb352 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -273,6 +273,7 @@ ActiveRecord::Schema.define do
     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|