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a Horizontal sharding support.
Defines a rudimental 'horizontal sharding' system which allows a Session to
distribute queries and persistence operations across multiple databases.
For a usage example, see the :ref:`examples_sharding` example included in
the source distribution.
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'' 11FO+v&&&& (33 3r Nc < |$ t t | j ||fd|i|S | j | }|r| | }| || D ],} t t | j ||fd|i|}||c S -dS )zOverride the default Query._identity_lookup method so that we
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r c 2 e Zd ZdZdZd Zed ZdS )r9 a A value object that represents multiple :class:`_engine.ResultProxy`
objects.
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an object that takes the place of the single :class:`_engine.ResultProxy`.
Attribute include ``result_proxies``, which is a sequence of the
actual :class:`_engine.ResultProxy` objects,
as well as ``aggregate_rowcount``
or ``rowcount``, which is the sum of all the individual rowcount values.
.. versionadded:: 1.3
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9I5 5 5 ' ' X' ' 'r r9 c B e Zd Zdef fd Zd ZddZ ddZd Z xZ S )r Nc t t | j dd|i| || _ || _ || _ i | _ | j | _ |!|D ] }| ||| dS dS )a Construct a ShardedSession.
:param shard_chooser: A callable which, passed a Mapper, a mapped
instance, and possibly a SQL clause, returns a shard ID. This id
may be based off of the attributes present within the object, or on
some round-robin scheme. If the scheme is based on a selection, it
should set whatever state on the instance to mark it in the future as
participating in that shard.
:param id_chooser: A callable, passed a query and a tuple of identity
values, which should return a list of shard ids where the ID might
reside. The databases will be queried in the order of this listing.
:param query_chooser: For a given Query, returns the list of shard_ids
where the query should be issued. Results from all shards returned
will be combined together into a single listing.
:param shards: A dictionary of string shard names
to :class:`~sqlalchemy.engine.Engine` objects.
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