code: func (p *Pipe) Batch(n int) *Pipe {
  	p.batchSize = n
  	return p
  }
docs: // Batch sets the batch size used when fetching documents from the database.
  // It's possible to change this setting on a per-session basis as well, using
  // the Batch method of Session.
  //
  // The default batch size is defined by the database server.