Merging PR #7

README.md

@@ -1,9 +1,9 @@
 mysql_online_migrations
 =======================
 
-Patch Rails migrations to enforce MySQL 5.6 online migrations  
+Patch Rails migrations to enforce MySQL 5.6 online migrations
 Prior to MySQL 5.6, when adding / removing / renaming indexes and columns, MySQL would lock the writes of the whole table.
-MySQL 5.6 by default will try to apply the least locking possible. You however don't know what kind of locking it applies and there's situations where it can't allow writes during a migration (See Caveats).  
+MySQL 5.6 by default will try to apply the least locking possible. You however don't know what kind of locking it applies and there's situations where it can't allow writes during a migration (See Caveats).
 This gem enforces `LOCK=NONE` in all migration statements of Rails. Therefore, you're getting an error when MySQL cannot write during the migration so there's no surprise when rolling out in production.
 
 
@@ -54,7 +54,15 @@ with_lock do
 end
 `````
 
-The `with_lock` method will be useful when hitting the caveats of `LOCK=NONE`. Please read the following section.
+The `with_lock` method will be useful when hitting the caveats of `LOCK=NONE`. Please read the 'Caveats' section.
+
+### Enable verbose output
+To enable an 'ONLINE MIGRATION' debug statement whenever an online migration is
+run, simply set the `MysqlOnlineMigrations.verbose` module variable to true.
+Example (in a Rails app's config/initializers/mysql_online_migrations.rb):
+````
+MysqlOnlineMigrations.verbose = true
+````
 
 Caveats
 =======================

lib/mysql_online_migrations.rb

@@ -7,6 +7,9 @@
 end
 
 module MysqlOnlineMigrations
+
+  class << self; attr_accessor :verbose; end
+
   def self.prepended(base)
     ActiveRecord::Base.send(:class_attribute, :mysql_online_migrations, :instance_writer => false)
     ActiveRecord::Base.send("mysql_online_migrations=", true)
@@ -22,7 +25,7 @@ def connection
       original_connection.instance_variable_get(:@delegate)
     end
 
-    @no_lock_adapter ||= ActiveRecord::ConnectionAdapters::Mysql2AdapterWithoutLock.new(@original_adapter)
+    @no_lock_adapter ||= ActiveRecord::ConnectionAdapters::Mysql2AdapterWithoutLock.new(@original_adapter, MysqlOnlineMigrations.verbose)
 
     if adapter_mode
       @no_lock_adapter
@@ -38,6 +41,7 @@ def with_lock
     yield
     ActiveRecord::Base.mysql_online_migrations = original_value
   end
+
 end
 
-ActiveRecord::Migration.send(:prepend, MysqlOnlineMigrations)
+ActiveRecord::Migration.send(:prepend, MysqlOnlineMigrations)

lib/mysql_online_migrations/mysql2_adapter_without_lock.rb

@@ -1,11 +1,13 @@
 module ActiveRecord
   module ConnectionAdapters
     class Mysql2AdapterWithoutLock < Mysql2Adapter
+
       OPTIMIZABLE_DDL_REGEX = /^(alter|create (unique )? ?index|drop index) /i
       DDL_WITH_COMMA_REGEX = /^alter /i
       DDL_WITH_LOCK_NONE_REGEX = / LOCK=NONE\s*$/i
 
-      def initialize(mysql2_adapter)
+      def initialize(mysql2_adapter, verbose = false)
+        @verbose = verbose
         params = [:@connection, :@logger, :@connection_options, :@config].map do |sym|
           mysql2_adapter.instance_variable_get(sym)
         end
@@ -24,9 +26,9 @@ def lock_none_statement(sql)
         return "" unless ActiveRecord::Base.mysql_online_migrations
         return "" if sql =~ DDL_WITH_LOCK_NONE_REGEX
         comma_delimiter = (sql =~ DDL_WITH_COMMA_REGEX ? "," : "")
-        puts "ONLINE MIGRATION"
+        puts "ONLINE MIGRATION" if @verbose
         "#{comma_delimiter} LOCK=NONE"
       end
     end
   end
-end
+end

spec/lib/mysql_online_migrations/mysql2_adapter_without_lock_spec.rb

@@ -5,6 +5,11 @@
     it "successfully instantiates a working adapter" do
       expect(ActiveRecord::ConnectionAdapters::Mysql2AdapterWithoutLock.new(@adapter)).to be_active
     end
+
+    it "successfully instantiates a working adapter with verbose output" do
+      instance = ActiveRecord::ConnectionAdapters::Mysql2AdapterWithoutLock.new(@adapter, true)
+      expect(instance.instance_variable_get(:@verbose)).to be_truthy
+    end
   end
 
   context "#lock_none_statement" do

spec/lib/mysql_online_migrations_spec.rb

@@ -10,10 +10,12 @@
   end
 
   context "#connection" do
-    shared_examples_for "Mysql2AdapterWithoutLock created" do
+    shared_examples_for "Mysql2AdapterWithoutLock created" do |verbose|
       it "memoizes an instance of Mysql2AdapterWithoutLock" do
+        MysqlOnlineMigrations.verbose = verbose
+
         expect(ActiveRecord::ConnectionAdapters::Mysql2AdapterWithoutLock).to receive(:new)
-          .with(an_instance_of(ActiveRecord::ConnectionAdapters::Mysql2Adapter)).once.and_call_original
+          .with(an_instance_of(ActiveRecord::ConnectionAdapters::Mysql2Adapter), verbose).once.and_call_original
         3.times { migration.connection }
       end
     end
@@ -26,6 +28,10 @@
       it_behaves_like "Mysql2AdapterWithoutLock created"
     end
 
+    context 'when migrating with verbose output' do
+      it_behaves_like "Mysql2AdapterWithoutLock created", true
+    end
+
     context 'when rolling back' do
       before do
         migration.instance_variable_set(:@connection, ActiveRecord::Migration::CommandRecorder.new(ActiveRecord::Base.connection))