def _variable_map_by_name(variables):
    """
    Returns Dict,representing referenced variable fields mapped by name.

    Keyword Parameters:
    variables  -- list of 'variable_python_type' Warehouse support DTOs

    >>> from pprint import pprint
    >>> var1 = { 'column':'frob_hz', 'title':'Frobniz Resonance (Hz)'
    ...         ,'python_type': 'float'
    ...         ,'table': 'foo_fact'}
    >>> list1 = [var1]
    >>> pprint(_variable_map_by_name(list1))
    {'frob_hz': {'column': 'frob_hz',
                 'python_type': 'float',
                 'table': 'foo_fact',
                 'title': 'Frobniz Resonance (Hz)'}}
    """
    variable_by_field = {}
    for var in variables:
        field_name = var['column']
        variable_by_field[field_name] = var
    return variable_by_field