'Return any spatial index creation SQL for the field.'

def sql_indexes_for_field(self, model, f, style):

    from django.contrib.gis.db.models.fields import GeometryField
    output = super(PostGISCreation, self).sql_indexes_for_field(model, f, style)
    if isinstance(f, GeometryField):
        gqn = self.connection.ops.geo_quote_name
        qn = self.connection.ops.quote_name
        db_table = model._meta.db_table
        if f.geography:
            pass
        else:
            output.append(((((((((((((style.SQL_KEYWORD('SELECT    ') + style.SQL_TABLE('AddGeometryColumn')) + '(') + style.SQL_TABLE(gqn(db_table))) + ',    ') + style.SQL_FIELD(gqn(f.column))) + ',    ') + style.SQL_FIELD(str(f.srid))) + ',    ') + style.SQL_COLTYPE(gqn(f.geom_type))) + ',    ') + style.SQL_KEYWORD(str(f.dim))) + ');'))
            if (not f.null):
                output.append((((((style.SQL_KEYWORD('ALTER    TABLE    ') + style.SQL_TABLE(qn(db_table))) + style.SQL_KEYWORD('    ALTER    ')) + style.SQL_FIELD(qn(f.column))) + style.SQL_KEYWORD('    SET    NOT    NULL')) + ';'))
        if f.spatial_index:
            if f.geography:
                index_opts = ''
            else:
                index_opts = ('    ' + style.SQL_KEYWORD(self.geom_index_opts))
            output.append((((((((((style.SQL_KEYWORD('CREATE    INDEX    ') + style.SQL_TABLE(qn(('%s_%s_id' % (db_table, f.column))))) + style.SQL_KEYWORD('    ON    ')) + style.SQL_TABLE(qn(db_table))) + style.SQL_KEYWORD('    USING    ')) + style.SQL_COLTYPE(self.geom_index_type)) + '    (    ') + style.SQL_FIELD(qn(f.column))) + index_opts) + '    );'))
    return output
