Add support for column limits in add_column_with_default

doc/development/migration_style_guide.md

@@ -111,6 +111,28 @@ class MyMigration < ActiveRecord::Migration
 end
 ```
 
+
+## Integer column type
+
+By default, an integer column can hold up to a 4-byte (32-bit) number. That is
+a max value of 2,147,483,647. Be aware of this when creating a column that will
+hold file sizes in byte units. If you are tracking file size in bytes this
+restricts the maximum file size to just over 2GB.
+
+To allow an integer column to hold up to an 8-byte (64-bit) number, explicitly
+set the limit to 8-bytes. This will allow the column to hold a value up to
+9,223,372,036,854,775,807.
+
+Rails migration example:
+
+```
+add_column_with_default(:projects, :foo, :integer, default: 10, limit: 8)
+
+# or
+
+add_column(:projects, :foo, :integer, default: 10, limit: 8)
+```
+
 ## Testing
 
 Make sure that your migration works with MySQL and PostgreSQL with data. An empty database does not guarantee that your migration is correct.

lib/gitlab/database/migration_helpers.rb

@@ -129,12 +129,14 @@ module Gitlab
       # column - The name of the column to add.
       # type - The column type (e.g. `:integer`).
       # default - The default value for the column.
+      # limit - Sets a column limit. For example, for :integer, the default is
+      #         4-bytes. Set `limit: 8` to allow 8-byte integers.
       # allow_null - When set to `true` the column will allow NULL values, the
       #              default is to not allow NULL values.
       #
       # This method can also take a block which is passed directly to the
       # `update_column_in_batches` method.
-      def add_column_with_default(table, column, type, default:, allow_null: false, &block)
+      def add_column_with_default(table, column, type, default:, limit: nil, allow_null: false, &block)
         if transaction_open?
           raise 'add_column_with_default can not be run inside a transaction, ' \
             'you can disable transactions by calling disable_ddl_transaction! ' \
@@ -144,7 +146,11 @@ module Gitlab
         disable_statement_timeout
 
         transaction do
+          if limit
+            add_column(table, column, type, default: nil, limit: limit)
+          else
             add_column(table, column, type, default: nil)
+          end
 
           # Changing the default before the update ensures any newly inserted
           # rows already use the proper default value.

spec/lib/gitlab/database/migration_helpers_spec.rb

@@ -91,6 +91,7 @@ describe Gitlab::Database::MigrationHelpers, lib: true do
 
   describe '#add_column_with_default' do
     context 'outside of a transaction' do
+      context 'when a column limit is not set' do
         before do
           expect(model).to receive(:transaction_open?).and_return(false)
 
@@ -151,6 +152,27 @@ describe Gitlab::Database::MigrationHelpers, lib: true do
         end
       end
 
+      context 'when a column limit is set' do
+        it 'adds the column with a limit' do
+          allow(model).to receive(:transaction_open?).and_return(false)
+          allow(model).to receive(:transaction).and_yield
+          expect(model).to receive(:add_column).
+            with(:projects, :foo, :integer, default: nil, limit: 8)
+          allow(model).to receive(:update_column_in_batches).
+            with(:projects, :foo, 10)
+          allow(model).to receive(:change_column_null).
+            with(:projects, :foo, false)
+          allow(model).to receive(:change_column_default).
+            with(:projects, :foo, 10)
+
+          expect(model).to receive(:add_column).
+            with(:projects, :foo, :integer, default: nil, limit: 8)
+
+          model.add_column_with_default(:projects, :foo, :integer, default: 10, limit: 8)
+        end
+      end
+    end
+
     context 'inside a transaction' do
       it 'raises RuntimeError' do
         expect(model).to receive(:transaction_open?).and_return(true)