text: CREATE TABLE tmp_filestore (
      file_id integer PRIMARY KEY,
      user_id integer NOT NULL,
      filename varchar(128) NOT NULL,
      mtime integer NOT NULL,
      data text NOT NULL
  );
  
  INSERT INTO tmp_filestore (file_id, user_id, filename, mtime, data)
      SELECT file_id, user_id, filename, mtime, data FROM filestore;
  
  DROP TABLE filestore;
  
  CREATE TABLE filestore (
      file_id integer NOT NULL PRIMARY KEY,
      user_id integer NOT NULL,
      context varchar(32) NOT NULL,
      filename varchar(128) NOT NULL,
      mtime integer NOT NULL,
      data text NOT NULL
  );
  
  INSERT INTO filestore (file_id, user_id, filename, mtime, data, context)
      SELECT file_id, user_id, filename, mtime, data, 'enigma' FROM tmp_filestore;
  
  CREATE UNIQUE INDEX ix_filestore_user_id ON filestore(user_id, context, filename);
  
  DROP TABLE tmp_filestore;
  
  