[6.1, 7.0, trunk] Cannot create manual many2many fields on models with long table names

[Stefan Rijnhart (Opener)]

On manually created many2many fields, the cross table is composed as follows:

    'x_' + target_model + '_' + source_model + '_' + field_name + '_rel'

Due to the relation length limit of 63 in Postgresql, you will run into trouble when both model names are a bit long. Although the table is created in that case with a truncated name, creating the indexes fails because these are created as

    cross_table + '_' + column_name + '_index'

Because the relation name length limit applies equally to the index, the truncated index name is equal to the truncated cross table name which raises an exception like

  File "/home/oerttrtst61/bzr/openobject-server/openerp/osv/orm.py", line 3174, in _m2m_raise_or_create_relation
    cr.execute('CREATE INDEX "%s_%s_index" ON "%s" ("%s")' % (m2m_tbl, col1, m2m_tbl, col1))
  File "/home/oerttrtst61/bzr/openobject-server/openerp/sql_db.py", line 152, in wrapper
    return f(self, *args, **kwargs)
  File "/home/oerttrtst61/bzr/openobject-server/openerp/sql_db.py", line 212, in execute
    res = self._obj.execute(query, params)
ProgrammingError: relation "x_magerp_product_attribute_options_product_template_x_magerp_br" already exists