View difference between Paste ID: H2j5xeBk and XFm71Cji

 class PRMigration extends Migration {
   public function __construct() {
     parent::__construct();
     $this->map = new MigrateSQLMap($this->machineName,
         array(
           'id' => array(
           	'type' => 'int',
             'not null' => TRUE,
             'description' => 'Press Release ID',
           )
         ),
         MigrateDestinationNode::getKeySchema()
       );
 
     $query = Database::getConnection('default', 'secondary')
              ->select('releases', 'r')
              ->fields('r', array('id', 'title', 'released_at', 'synopsis', 'body',
              	 'never_post', 'position', 'writer', 'created_by', 'updated_by',
              	 'created_at', 'updated_at', 'subtitle', 'contact_id',
              	 'version', 'deleted_at'));
 
     $source_fields = array(
       'links' => t('Related links'),
       'source_images' => t('Image assets attached ot this press release.'),
     );
     $this->source = new MigrateSourceSQL($query, $source_fields, NULL, array('map_joinable' => FALSE));
     // Using the default Node destination class.
     $this->destination = new MigrateDestinationNode('press_release');
 
     ///////////////////////////////////////////////////////
     // Mapped fields
     ///////////////////////////////////////////////////////
     $file_args = MigrateFileFieldHandler::arguments(NULL, 'file_blob', FILE_EXISTS_RENAME);
     $this->addFieldMapping('field_image', 'source_images')
          ->arguments($file_args);
 
   }
   public function prepareRow($row) {
     // Pull in the associated images for this release.
     $source_db = Database::getConnection('default', 'secondary');
     $query = $source_db
              ->select('assets', 'a')
              ->fields('a', array('id', 'filename', 'content_type', 'alt', 'caption',
              	 'photo_credit', 'size', 'height', 'width', 'parent_id', 'thumbnail',
              	 'db_file_id', 'created_by', 'updated_by', 'created_at', 'updated_at'));
     $query->innerJoin('db_files', 'dbf', 'a.db_file_id = dbf.id');
     $query->addField('dbf', 'data');
     $query->leftJoin('assignments', 'assign', 'a.id = assign.asset_id');
     $query->condition('assign.category_type', 'Release', '=');
     $query->condition('assign.category_id', $row->id, '=');
     $results = $query->execute();
 
     $images = array();
 
     foreach ($results as $row) {
       $image_information = array(
         'path' => $row->filename,
         'alt' => $row->alt,
         'title' => $row->caption,
       	'contents' => $row->data,
       );
       $images[] = drupal_json_encode($image_information);
 
     }
 
     $row->source_images = $images;
     return TRUE;
   }
 }
 
 class PRAssetMigration extends Migration {
   public function __construct() {
     parent::__construct();
 
     $this->map = new MigrateSQLMap($this->machineName,
         array(
           'id' => array(
           	'type' => 'int',
             'not null' => TRUE,
             'description' => 'Asset ID',
           )
         ),
         MigrateDestinationNode::getKeySchema()
       );
 
     // Select all the fields from the 'assets' table, and join it with the related 'data' field in db_files.
     $source_db = Database::getConnection('default', 'secondary');
     $query = $source_db
              ->select('assets', 'a')
              ->fields('a', array('id', 'filename', 'content_type', 'alt', 'caption',
              	 'photo_credit', 'size', 'height', 'width', 'parent_id', 'thumbnail',
              	 'db_file_id', 'created_by', 'updated_by', 'created_at', 'updated_at'));
     $query->innerJoin('db_files', 'dbf', 'a.db_file_id = dbf.id');
     $query->addField('dbf', 'data');
     $count_query = $source_db->select('assets', 'a');
     $count_query->addExpression('COUNT(id)', 'cnt');
 
     // User the simplified count query so it doesn't have to do the join to get the count.
     $this->source = new MigrateSourceSQL($query, array(), $count_query, array('map_joinable' => FALSE));
     $this->destination = new MigrateDestinationFile(MigrateDestinationFile::options(FALSE, NULL, NULL, NULL, FALSE, TRUE));
 
     ///////////////////////////////////////////////////////
     // Mapped fields
     ///////////////////////////////////////////////////////
     $this->addSimpleMappings(array());
 
     $this->addFieldMapping('contents', 'data');
     $this->addFieldMapping('filename', 'filename')
          ->dedupe('file_managed', 'filename');
     $this->addFieldMapping('filemime', 'content_type');
     // Since we don't care about the history of the source files, use updated_at instead of created_at.
     $this->addFieldMapping('timestamp', 'updated_at');
 
 
     ///////////////////////////////////////////////////////
     // Unmapped Source fields
     ///////////////////////////////////////////////////////
     $this->addUnmigratedSources(array('db_file_id', 'created_by', 'updated_by', 'created_at'));
 
     ///////////////////////////////////////////////////////
     // Unmapped destination fields
     ///////////////////////////////////////////////////////
     $this->addUnmigratedDestinations(array('uri', 'path', 'uid'));
 
 
   }
 }