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Horizontal Sharding
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SQLAlchemy 1.2 Documentation
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Release: <span class="version-num">1.2.19</span>
| Release Date: April 15, 2019
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<h1>SQLAlchemy 1.2 Documentation</h1>
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<a href="../index.html" title="SQLAlchemy ORM">SQLAlchemy ORM</a>
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<div class="section" id="module-sqlalchemy.ext.horizontal_shard">
<span id="horizontal-sharding"></span><span id="horizontal-sharding-toplevel"></span><h1>Horizontal Sharding<a class="headerlink" href="#module-sqlalchemy.ext.horizontal_shard" title="Permalink to this headline">¶</a></h1>
<p>Horizontal sharding support.</p>
<p>Defines a rudimental ‘horizontal sharding’ system which allows a Session to
distribute queries and persistence operations across multiple databases.</p>
<p>For a usage example, see the <a class="reference internal" href="../examples.html#examples-sharding"><span class="std std-ref">Horizontal Sharding</span></a> example included in
the source distribution.</p>
<div class="section" id="api-documentation">
<h2>API Documentation<a class="headerlink" href="#api-documentation" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="sqlalchemy.ext.horizontal_shard.ShardedSession">
<em class="property">class </em><code class="descclassname">sqlalchemy.ext.horizontal_shard.</code><code class="descname">ShardedSession</code><span class="sig-paren">(</span><em>shard_chooser</em>, <em>id_chooser</em>, <em>query_chooser</em>, <em>shards=None</em>, <em>query_cls=<class 'sqlalchemy.ext.horizontal_shard.ShardedQuery'></em>, <em>**kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#sqlalchemy.ext.horizontal_shard.ShardedSession" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">sqlalchemy.orm.session.Session</span></code></a></p>
<dl class="method">
<dt id="sqlalchemy.ext.horizontal_shard.ShardedSession.__init__">
<code class="descname">__init__</code><span class="sig-paren">(</span><em>shard_chooser</em>, <em>id_chooser</em>, <em>query_chooser</em>, <em>shards=None</em>, <em>query_cls=<class 'sqlalchemy.ext.horizontal_shard.ShardedQuery'></em>, <em>**kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.__init__" title="Permalink to this definition">¶</a></dt>
<dd><p>Construct a ShardedSession.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters</dt>
<dd class="field-odd"><ul class="simple">
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.params.shard_chooser"></span><strong>shard_chooser</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.params.shard_chooser">¶</a> – 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.</p></li>
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.params.id_chooser"></span><strong>id_chooser</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.params.id_chooser">¶</a> – 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.</p></li>
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.params.query_chooser"></span><strong>query_chooser</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.params.query_chooser">¶</a> – 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.</p></li>
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.params.shards"></span><strong>shards</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.params.shards">¶</a> – A dictionary of string shard names
to <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Engine" title="sqlalchemy.engine.Engine"><code class="xref py py-class docutils literal notranslate"><span class="pre">Engine</span></code></a> objects.</p></li>
</ul>
</dd>
</dl>
</dd></dl>
<dl class="method">
<dt id="sqlalchemy.ext.horizontal_shard.ShardedSession.connection">
<code class="descname">connection</code><span class="sig-paren">(</span><em>mapper=None</em>, <em>instance=None</em>, <em>shard_id=None</em>, <em>**kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.connection" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Connection" title="sqlalchemy.engine.Connection"><code class="xref py py-class docutils literal notranslate"><span class="pre">Connection</span></code></a> object corresponding to this
<a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a> object’s transactional state.</p>
<p>If this <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a> is configured with <code class="docutils literal notranslate"><span class="pre">autocommit=False</span></code>,
either the <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Connection" title="sqlalchemy.engine.Connection"><code class="xref py py-class docutils literal notranslate"><span class="pre">Connection</span></code></a> corresponding to the current
transaction is returned, or if no transaction is in progress, a new
one is begun and the <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Connection" title="sqlalchemy.engine.Connection"><code class="xref py py-class docutils literal notranslate"><span class="pre">Connection</span></code></a> returned (note that no
transactional state is established with the DBAPI until the first
SQL statement is emitted).</p>
<p>Alternatively, if this <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a> is configured with
<code class="docutils literal notranslate"><span class="pre">autocommit=True</span></code>, an ad-hoc <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Connection" title="sqlalchemy.engine.Connection"><code class="xref py py-class docutils literal notranslate"><span class="pre">Connection</span></code></a> is returned
using <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Engine.contextual_connect" title="sqlalchemy.engine.Engine.contextual_connect"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Engine.contextual_connect()</span></code></a> on the underlying
<a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Engine" title="sqlalchemy.engine.Engine"><code class="xref py py-class docutils literal notranslate"><span class="pre">Engine</span></code></a>.</p>
<p>Ambiguity in multi-bind or unbound <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a> objects can be
resolved through any of the optional keyword arguments. This
ultimately makes usage of the <a class="reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind" title="sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_bind()</span></code></a> method for resolution.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters</dt>
<dd class="field-odd"><ul class="simple">
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.bind"></span><strong>bind</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.bind">¶</a> – Optional <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Engine" title="sqlalchemy.engine.Engine"><code class="xref py py-class docutils literal notranslate"><span class="pre">Engine</span></code></a> to be used as the bind. If
this engine is already involved in an ongoing transaction,
that connection will be used. This argument takes precedence
over <code class="docutils literal notranslate"><span class="pre">mapper</span></code>, <code class="docutils literal notranslate"><span class="pre">clause</span></code>.</p></li>
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.mapper"></span><strong>mapper</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.mapper">¶</a> – Optional <a class="reference internal" href="../mapping_api.html#sqlalchemy.orm.mapper" title="sqlalchemy.orm.mapper"><code class="xref py py-func docutils literal notranslate"><span class="pre">mapper()</span></code></a> mapped class, used to identify
the appropriate bind. This argument takes precedence over
<code class="docutils literal notranslate"><span class="pre">clause</span></code>.</p></li>
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.clause"></span><strong>clause</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.clause">¶</a> – A <a class="reference internal" href="../../core/sqlelement.html#sqlalchemy.sql.expression.ClauseElement" title="sqlalchemy.sql.expression.ClauseElement"><code class="xref py py-class docutils literal notranslate"><span class="pre">ClauseElement</span></code></a> (i.e. <a class="reference internal" href="../../core/selectable.html#sqlalchemy.sql.expression.select" title="sqlalchemy.sql.expression.select"><code class="xref py py-func docutils literal notranslate"><span class="pre">select()</span></code></a>,
<a class="reference internal" href="../../core/sqlelement.html#sqlalchemy.sql.expression.text" title="sqlalchemy.sql.expression.text"><code class="xref py py-func docutils literal notranslate"><span class="pre">text()</span></code></a>,
etc.) which will be used to locate a bind, if a bind
cannot otherwise be identified.</p></li>
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.close_with_result"></span><strong>close_with_result</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.close_with_result">¶</a> – Passed to <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Engine.connect" title="sqlalchemy.engine.Engine.connect"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Engine.connect()</span></code></a>,
indicating the <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Connection" title="sqlalchemy.engine.Connection"><code class="xref py py-class docutils literal notranslate"><span class="pre">Connection</span></code></a> should be considered
“single use”, automatically closing when the first result set is
closed. This flag only has an effect if this <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a> is
configured with <code class="docutils literal notranslate"><span class="pre">autocommit=True</span></code> and does not already have a
transaction in progress.</p></li>
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.execution_options"></span><strong>execution_options</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.execution_options">¶</a> – <p>a dictionary of execution options that will
be passed to <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Connection.execution_options" title="sqlalchemy.engine.Connection.execution_options"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Connection.execution_options()</span></code></a>, <strong>when the
connection is first procured only</strong>. If the connection is already
present within the <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a>, a warning is emitted and
the arguments are ignored.</p>
<div class="versionadded">
<p><span class="versionmodified added">New in version 0.9.9.</span></p>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="../session_transaction.html#session-transaction-isolation"><span class="std std-ref">Setting Transaction Isolation Levels</span></a></p>
</div>
</p></li>
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.**kw"></span><strong>**kw</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.connection.params.**kw">¶</a> – Additional keyword arguments are sent to <a class="reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind" title="sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_bind()</span></code></a>,
allowing additional arguments to be passed to custom
implementations of <a class="reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind" title="sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_bind()</span></code></a>.</p></li>
</ul>
</dd>
</dl>
</dd></dl>
<dl class="method">
<dt id="sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind">
<code class="descname">get_bind</code><span class="sig-paren">(</span><em>mapper</em>, <em>shard_id=None</em>, <em>instance=None</em>, <em>clause=None</em>, <em>**kw</em><span class="sig-paren">)</span><a class="headerlink" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a “bind” to which this <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a> is bound.</p>
<p>The “bind” is usually an instance of <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Engine" title="sqlalchemy.engine.Engine"><code class="xref py py-class docutils literal notranslate"><span class="pre">Engine</span></code></a>,
except in the case where the <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a> has been
explicitly bound directly to a <a class="reference internal" href="../../core/connections.html#sqlalchemy.engine.Connection" title="sqlalchemy.engine.Connection"><code class="xref py py-class docutils literal notranslate"><span class="pre">Connection</span></code></a>.</p>
<p>For a multiply-bound or unbound <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a>, the
<code class="docutils literal notranslate"><span class="pre">mapper</span></code> or <code class="docutils literal notranslate"><span class="pre">clause</span></code> arguments are used to determine the
appropriate bind to return.</p>
<p>Note that the “mapper” argument is usually present
when <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session.get_bind" title="sqlalchemy.orm.session.Session.get_bind"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Session.get_bind()</span></code></a> is called via an ORM
operation such as a <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session.query" title="sqlalchemy.orm.session.Session.query"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Session.query()</span></code></a>, each
individual INSERT/UPDATE/DELETE operation within a
<a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session.flush" title="sqlalchemy.orm.session.Session.flush"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Session.flush()</span></code></a>, call, etc.</p>
<p>The order of resolution is:</p>
<ol class="arabic simple">
<li><p>if mapper given and session.binds is present,
locate a bind based first on the mapper in use, then
on the mapped class in use, then on any base classes that are
present in the <code class="docutils literal notranslate"><span class="pre">__mro__</span></code> of the mapped class, from more specific
superclasses to more general.</p></li>
<li><p>if clause given and session.binds is present,
locate a bind based on <a class="reference internal" href="../../core/metadata.html#sqlalchemy.schema.Table" title="sqlalchemy.schema.Table"><code class="xref py py-class docutils literal notranslate"><span class="pre">Table</span></code></a> objects
found in the given clause present in session.binds.</p></li>
<li><p>if session.bind is present, return that.</p></li>
<li><p>if clause given, attempt to return a bind
linked to the <a class="reference internal" href="../../core/metadata.html#sqlalchemy.schema.MetaData" title="sqlalchemy.schema.MetaData"><code class="xref py py-class docutils literal notranslate"><span class="pre">MetaData</span></code></a> ultimately
associated with the clause.</p></li>
<li><p>if mapper given, attempt to return a bind
linked to the <a class="reference internal" href="../../core/metadata.html#sqlalchemy.schema.MetaData" title="sqlalchemy.schema.MetaData"><code class="xref py py-class docutils literal notranslate"><span class="pre">MetaData</span></code></a> ultimately
associated with the <a class="reference internal" href="../../core/metadata.html#sqlalchemy.schema.Table" title="sqlalchemy.schema.Table"><code class="xref py py-class docutils literal notranslate"><span class="pre">Table</span></code></a> or other
selectable to which the mapper is mapped.</p></li>
<li><p>No bind can be found, <a class="reference internal" href="../../core/exceptions.html#sqlalchemy.exc.UnboundExecutionError" title="sqlalchemy.exc.UnboundExecutionError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">UnboundExecutionError</span></code></a>
is raised.</p></li>
</ol>
<p>Note that the <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session.get_bind" title="sqlalchemy.orm.session.Session.get_bind"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Session.get_bind()</span></code></a> method can be overridden on
a user-defined subclass of <a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a> to provide any kind
of bind resolution scheme. See the example at
<a class="reference internal" href="../persistence_techniques.html#session-custom-partitioning"><span class="std std-ref">Custom Vertical Partitioning</span></a>.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters</dt>
<dd class="field-odd"><ul class="simple">
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind.params.mapper"></span><strong>mapper</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind.params.mapper">¶</a> – Optional <a class="reference internal" href="../mapping_api.html#sqlalchemy.orm.mapper" title="sqlalchemy.orm.mapper"><code class="xref py py-func docutils literal notranslate"><span class="pre">mapper()</span></code></a> mapped class or instance of
<a class="reference internal" href="../mapping_api.html#sqlalchemy.orm.mapper.Mapper" title="sqlalchemy.orm.mapper.Mapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">Mapper</span></code></a>. The bind can be derived from a <a class="reference internal" href="../mapping_api.html#sqlalchemy.orm.mapper.Mapper" title="sqlalchemy.orm.mapper.Mapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">Mapper</span></code></a>
first by consulting the “binds” map associated with this
<a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><code class="xref py py-class docutils literal notranslate"><span class="pre">Session</span></code></a>, and secondly by consulting the <a class="reference internal" href="../../core/metadata.html#sqlalchemy.schema.MetaData" title="sqlalchemy.schema.MetaData"><code class="xref py py-class docutils literal notranslate"><span class="pre">MetaData</span></code></a>
associated with the <a class="reference internal" href="../../core/metadata.html#sqlalchemy.schema.Table" title="sqlalchemy.schema.Table"><code class="xref py py-class docutils literal notranslate"><span class="pre">Table</span></code></a> to which the <a class="reference internal" href="../mapping_api.html#sqlalchemy.orm.mapper.Mapper" title="sqlalchemy.orm.mapper.Mapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">Mapper</span></code></a>
is mapped for a bind.</p></li>
<li><p><span class="target" id="sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind.params.clause"></span><strong>clause</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.ext.horizontal_shard.ShardedSession.get_bind.params.clause">¶</a> – A <a class="reference internal" href="../../core/sqlelement.html#sqlalchemy.sql.expression.ClauseElement" title="sqlalchemy.sql.expression.ClauseElement"><code class="xref py py-class docutils literal notranslate"><span class="pre">ClauseElement</span></code></a> (i.e. <a class="reference internal" href="../../core/selectable.html#sqlalchemy.sql.expression.select" title="sqlalchemy.sql.expression.select"><code class="xref py py-func docutils literal notranslate"><span class="pre">select()</span></code></a>,
<a class="reference internal" href="../../core/sqlelement.html#sqlalchemy.sql.expression.text" title="sqlalchemy.sql.expression.text"><code class="xref py py-func docutils literal notranslate"><span class="pre">text()</span></code></a>,
etc.). If the <code class="docutils literal notranslate"><span class="pre">mapper</span></code> argument is not present or could not
produce a bind, the given expression construct will be searched
for a bound element, typically a <a class="reference internal" href="../../core/metadata.html#sqlalchemy.schema.Table" title="sqlalchemy.schema.Table"><code class="xref py py-class docutils literal notranslate"><span class="pre">Table</span></code></a> associated with
bound <a class="reference internal" href="../../core/metadata.html#sqlalchemy.schema.MetaData" title="sqlalchemy.schema.MetaData"><code class="xref py py-class docutils literal notranslate"><span class="pre">MetaData</span></code></a>.</p></li>
</ul>
</dd>
</dl>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="../persistence_techniques.html#session-partitioning"><span class="std std-ref">Partitioning Strategies (e.g. multiple database backends per Session)</span></a></p>
<p><a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session.params.binds" title="sqlalchemy.orm.session.Session"><code class="xref py py-paramref docutils literal notranslate"><span class="pre">Session.binds</span></code></a></p>
<p><a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session.bind_mapper" title="sqlalchemy.orm.session.Session.bind_mapper"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Session.bind_mapper()</span></code></a></p>
<p><a class="reference internal" href="../session_api.html#sqlalchemy.orm.session.Session.bind_table" title="sqlalchemy.orm.session.Session.bind_table"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Session.bind_table()</span></code></a></p>
</div>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="sqlalchemy.ext.horizontal_shard.ShardedQuery">
<em class="property">class </em><code class="descclassname">sqlalchemy.ext.horizontal_shard.</code><code class="descname">ShardedQuery</code><span class="sig-paren">(</span><em>*args</em>, <em>**kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#sqlalchemy.ext.horizontal_shard.ShardedQuery" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="../query.html#sqlalchemy.orm.query.Query" title="sqlalchemy.orm.query.Query"><code class="xref py py-class docutils literal notranslate"><span class="pre">sqlalchemy.orm.query.Query</span></code></a></p>
<dl class="method">
<dt id="sqlalchemy.ext.horizontal_shard.ShardedQuery.set_shard">
<code class="descname">set_shard</code><span class="sig-paren">(</span><em>shard_id</em><span class="sig-paren">)</span><a class="headerlink" href="#sqlalchemy.ext.horizontal_shard.ShardedQuery.set_shard" title="Permalink to this definition">¶</a></dt>
<dd><p>return a new query, limited to a single shard ID.</p>
<p>all subsequent operations with the returned query will
be against the single shard regardless of other state.</p>
</dd></dl>
</dd></dl>
</div>
</div>
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