Really, `mapper` contains this: <sqlalchemy.sql.selectable.CTE at
0x7fe673fb0a50; group_getter>. But does it changes something? I already
encountered this problem in my code, when I checked sqla-objects existance
without "is not None", project was broken. Is it normal to omit that
condition in sqlalchemy code?
I use:
>>> sqlalchemy.__version__
'1.0.19'
пятница, 20 октября 2017 г., 16:42:23 UTC+3 пользователь Simon King написал:
>
> On Fri, Oct 20, 2017 at 2:15 PM, Антонио Антуан <a.ch...@gmail.com
> <javascript:>> wrote:
> > Hi.
> > I use my own `RoutingSession` and `RoutingQuery` implementation, most of
> it
> > inspired by `sqlalchemy.ext.horizontal_shard`:
> >
> > class RoutingSession(Session):
> > def get_bind(self, mapper=None, clause=None, shard_id=None,
> **kwargs):
> > original_bind = None
> > try:
> > original_bind = super(RoutingSession, self).get_bind(mapper,
> > clause)
> > except UnboundExecutionError:
> > # may not be bound
> > pass
> > if shard_id is None:
> > shard_id = TenantIDStorage.get_shard_id() # just global
> storage
> > bind_for_shard = self.__binds[shard_id]
> > if original_bind is not None and original_bind.url ==
> > bind_for_shard.url:
> > return original_bind
> > else:
> > return bind_for_shard
> >
> > def __init__(self, shards=None, query_cls=CachingQuery,
> > engines_factory=None, **kwargs):
> > super(RoutingSession, self).__init__(query_cls=query_cls,
> **kwargs)
> > self.__binds = {}
> > self.engines_factory = engines_factory
> > if shards is not None:
> > self.update_shards(**shards)
> >
> > def _add_bind(self, key, bind):
> > self.__binds[key] = bind
> >
> >
> >
> >
> > class RoutingQuery(Query):
> > def __init__(self, *args, **kwargs):
> > super(RoutingQuery, self).__init__(*args, **kwargs)
> > self._shard_id = TenantIDStorage.get_shard_id()
> >
> > def get(self, ident):
> > self._check_bound_to_shard()
> > return super(CachingQuery, self).get(ident)
> >
> > def _check_bound_to_shard(self):
> > if self._shard_id is None:
> > raise ValueError('query not bound to any shard')
> >
> > def _execute_and_instances(self, querycontext):
> > self._check_bound_to_shard()
> > querycontext.attributes['shard_id'] = self._shard_id
> > result = self._connection_from_session(
> > mapper=self._mapper_zero(),
> > shard_id=self._shard_id).execute(
> > querycontext.statement,
> > self._params
> > )
> > return self.instances(result, querycontext)
> >
> >
> >
> >
> >
> >
> > Sometimes I got this error:
> >
> > File "/home/anton/Projects/proj/admin/proj/admin/views/stats.py", line
> > 898, in _get_filters_from_request
> > control_groups = [g.id for g in
> > User.get_own_groups_query(current_user.id)]
> > File
> >
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/orm/query.py",
>
>
> > line 2802, in __iter__
> > return self._execute_and_instances(context)
> > File
> >
> "/home/anton/Projects/proj/core/proj/core/orm_extensions/rouing_session.py",
>
> > line 105, in _execute_and_instances
> > shard_id=self._shard_id).execute(
> > File
> >
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/orm/query.py",
>
>
> > line 2806, in _connection_from_session
> > **kw)
> > File
> >
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/orm/session.py",
>
>
> > line 984, in connection
> > bind = self.get_bind(mapper, clause=clause, **kw)
> > File
> >
> "/home/anton/Projects/proj/core/proj/core/orm_extensions/cachingquery.py",
> > line 279, in get_bind
> > original_bind = super(RoutingSession, self).get_bind(mapper, clause)
> > File
> >
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/orm/session.py",
>
>
> > line 1336, in get_bind
> > if mapper and mapper.mapped_table.bind:
> > File
> >
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/elements.py",
>
>
> > line 539, in __bool__
> > raise TypeError("Boolean value of this clause is not defined")
> > TypeError: Boolean value of this clause is not defined
> >
> >
> >
> >
> > I found that `mapper` in original `get_bind` always checks with `is not
> > None` condition. There is only one place where condition omitted: `if
> mapper
> > and mapper.mapped_table.bind...`.
> > Possibly it is not correct? Or my code does not do something important?
>
> Are you able to catch this error in a debugger?
>
> I'm going to make a wild guess that "mapper" at this point is some
> sort of SQL construct (such as a column object or mapped property),
> rather than an actual mapper.
>
> You don't say which version of SQLAlchemy you are using, but since
> you've overridden _execute_and_instances, I wonder if you need to use
> something like query._bind_mapper() as used by _get_bind_args:
>
> <
> https://bitbucket.org/zzzeek/sqlalchemy/src/4b22b01ade6f94cc4db2f2040c802067a25d29a4/lib/sqlalchemy/orm/query.py?at=rel_1_1_14&fileviewer=file-view-default#query.py-2872>
>
>
>
> Hope that helps,
>
> Simon
>
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