Added preliminary support for an agile database migration technique (currently only for MySQL)

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@818 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

4 files changed, 187 insertions, 11 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 605a82bf74..d686d71246 100755
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -356,6 +356,38 @@ module ActiveRecord
         sql << " LIMIT #{limit}"
       end
 
+
+      def initialize_schema_information
+        begin
+          execute "CREATE TABLE schema_info (version #{native_database_types[:integer]})"
+          insert "INSERT INTO schema_info (version) VALUES(0)"
+        rescue ActiveRecord::StatementInvalid
+          # Schema has been intialized
+        end
+      end
+
+      def create_table(name)
+        execute "CREATE TABLE #{name} (id #{native_database_types[:primary_key]})"
+        table_definition = yield TableDefinition.new
+        table_definition.columns.each { |column_name, type, options| add_column(name, column_name, type, options) }
+      end
+
+      def drop_table(name)
+        execute "DROP TABLE #{name}"
+      end
+
+      def add_column(table_name, column_name, type, options = {})
+        add_column_sql = "ALTER TABLE #{table_name} ADD #{column_name} #{native_database_types[type]}"
+        add_column_sql << "(#{limit})" if options[:limit]
+        add_column_sql << " DEFAULT '#{options[:default]}'" if options[:default]
+        execute(add_column_sql)
+      end
+
+      def remove_column(table_name, column_name)
+        execute "ALTER TABLE #{table_name} DROP #{column_name}"
+      end
+
+
       protected
         def log(sql, name, connection = nil)
           connection ||= @connection
@@ -402,6 +434,18 @@ module ActiveRecord
           log_entry
         end
     end
-    
+
+    class TableDefinition
+      attr_accessor :columns
+      
+      def initialize
+        @columns = []
+      end
+
+      def column(name, type, options = {})
+        @columns << [ name, type, options ]
+        self
+      end
+    end
   end
-end
+end
\ No newline at end of file
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index cf7c700b66..0c78b921b6 100755
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -63,12 +63,33 @@ module ActiveRecord
         "Lost connection to MySQL server during query", 
         "MySQL server has gone away"
       ]
-      
+
+      def native_database_types
+        {
+          :primary_key => "int(11) DEFAULT NULL auto_increment PRIMARY KEY",
+          :string      => "varchar(255)",
+          :text        => "text",
+          :integer     => "int(11)",
+          :float       => "float",
+          :datetime    => "datetime",
+          :timestamp   => "datetime",
+          :time        => "datetime",
+          :date        => "date",
+          :binary      => "blob",
+          :boolean     => "tinyint(1)"
+        }
+      end
+
       def initialize(connection, logger, connection_options=nil)
         super(connection, logger)
         @connection_options = connection_options
       end
  
+      def adapter_name
+        'MySQL'
+      end
+
+
       def select_all(sql, name = nil)
         select(sql, name)
       end
@@ -111,6 +132,7 @@ module ActiveRecord
  
       alias_method :delete, :update
  
+ 
       def begin_db_transaction
         begin
           execute "BEGIN"
@@ -134,15 +156,17 @@ module ActiveRecord
           # Transactions aren't supported
         end
       end
+
  
       def quote_column_name(name)
         return "`#{name}`"
       end
  
-      def adapter_name()
-        'MySQL'
+      def quote_string(s)
+        Mysql::quote(s)
       end
- 
+
+
       def structure_dump
         select_all("SHOW TABLES").inject("") do |structure, table|
           structure += select_one("SHOW CREATE TABLE #{table.to_a.first.last}")["Create Table"] + ";\n\n"
@@ -161,11 +185,8 @@ module ActiveRecord
       def create_database(name)
         execute "CREATE DATABASE #{name}"
       end
- 
-      def quote_string(s)
-        Mysql::quote(s)
-      end
- 
+
+
       private
         def select(sql, name = nil)
           result = nil
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
index 4958094ecb..ba786667cf 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
@@ -87,6 +87,22 @@ module ActiveRecord
     #
     # * <tt>:dbfile</tt> -- Path to the database file.
     class SQLiteAdapter < AbstractAdapter
+      def native_database_types
+        {
+          :primary_key => "INTEGER PRIMARY KEY NOT NULL",
+          :string      => "VARCHAR(255)",
+          :text        => "TEXT",
+          :integer     => "INTEGER",
+          :float       => "float",
+          :datetime    => "DATETIME",
+          :timestamp   => "DATETIME",
+          :time        => "DATETIME",
+          :date        => "DATE",
+          :binary      => "BLOB",
+          :boolean     => "INTEGER"
+        }
+      end
+
       def execute(sql, name = nil)
         log(sql, name) { @connection.execute(sql) }
       end
@@ -150,6 +166,7 @@ module ActiveRecord
         'SQLite'
       end
 
+
       protected
         def table_structure(table_name)
           execute "PRAGMA table_info(#{table_name})"
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
new file mode 100644
index 0000000000..8734a0831e
--- /dev/null
+++ b/activerecord/lib/active_record/migration.rb
@@ -0,0 +1,94 @@
+module ActiveRecord
+  class IrreversibleMigration < ActiveRecordError
+  end
+  
+  class Migration
+    class << self
+      def up() end
+      def down() end
+
+      private
+        def method_missing(method, *arguments, &block)
+          ActiveRecord::Base.connection.send(method, *arguments, &block)
+        end
+    end
+  end
+
+  class Migrator
+    class << self
+      def up(migrations_path, target_version = nil)
+        new(:up, migrations_path, target_version).migrate
+      end
+      
+      def down(migrations_path, target_version = nil)
+        new(:down, migrations_path, target_version).migrate
+      end
+      
+      def current_version
+        Base.connection.select_one("SELECT version FROM schema_info")["version"].to_i
+      end
+    end
+    
+    def initialize(direction, migrations_path, target_version = nil)
+      @direction, @migrations_path, @target_version = direction, migrations_path, target_version
+    end
+
+    def current_version
+      self.class.current_version
+    end
+
+    def migrate
+      migration_classes do |version, migration_class|
+        Base.logger.info("Reached target version: #{@target_version}") and break if reached_target_version?(version)
+        next if irrelevant_migration?(version)
+
+        Base.logger.info "Migrating to #{migration_class} (#{version})"
+        migration_class.send(@direction)
+
+        set_schema_version(version)
+      end
+    end
+
+    private
+      def migration_classes
+        for migration_file in migration_files
+          load(migration_file)
+          version, name = migration_version_and_name(migration_file)
+          yield version, migration_class(name)
+        end
+      end
+    
+      def migration_files
+        files = Dir["#{@migrations_path}/[0-9]*_*.rb"]
+        down? ? files.reverse : files
+      end
+      
+      def migration_class(migration_name)
+        migration_name.camelize.constantize
+      end
+    
+      def migration_version_and_name(migration_file)
+        return *migration_file.scan(/([0-9]+)_([_a-z0-9]*).rb/).first
+      end
+      
+      def set_schema_version(version)
+        Base.connection.update("UPDATE schema_info SET version = #{down? ? version.to_i - 1 : version.to_i}")
+      end
+      
+      def up?
+        @direction == :up
+      end
+      
+      def down?
+        @direction == :down
+      end
+      
+      def reached_target_version?(version)
+        (up? && version.to_i - 1 == @target_version) || (down? && version.to_i == @target_version)
+      end
+      
+      def irrelevant_migration?(version)
+        (up? && version.to_i <= current_version) || (down? && version.to_i > current_version)
+      end
+  end
+end
\ No newline at end of file