[entity] ensure the .related(entities=False) parameter is honored all the way down (closes #2755994)
As of today, such a call will always fill the relation cache by
calling .entities() on every single related rset entry.
As a consequence, the `limit` parameter handling also had to be fixed.
It was bogus in the following ways:
* not used in the related_rql, hence potentially huge database
requests, but also actually
* foolishly used in the .entities()-calling cache routine we now
bypass (this changeset ticket's main topic)
Now:
* we set a limit on the rql expression, and
* forbid caching if given a non-None limit (as we don't want to make
the cache handling code more complicated than it is already)
With this, entity.unrelated gets a better limit implementation (so the
code in related/unrelated is nice and symmetric)
Risk:
* _cw_relation_cache disappears completely, which is good, but this is
Python, so you never know ...
# pylint: disable=W0614,W0401
# copyright 2003-2010 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of CubicWeb.
#
# CubicWeb is free software: you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option)
# any later version.
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# details.
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# You should have received a copy of the GNU Lesser General Public License along
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from warnings import warn
warn('moved to cubicweb.dataimport', DeprecationWarning, stacklevel=2)
from cubicweb.dataimport import *