code: func (t *Table) getColumn(name string) (NonAliasColumn, error) {
  	if c, ok := t.columnLookup[name]; ok {
  		return c, nil
  	}
  	return nil, errors.Newf("No such column '%s' in table '%s'", name, t.name)
  }
docs: // Returns the specified column, or errors if it doesn't exist in the table