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  • Committer: Package Import Robot
  • Author(s): Piotr Ożarowski
  • Date: 2013-10-28 22:29:40 UTC
  • mfrom: (1.4.24)
  • Revision ID: package-import@ubuntu.com-20131028222940-wvyqffl4g617caun
Tags: 0.8.3-1
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doc/orm/inheritance.html
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    <script type="text/javascript">
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      var DOCUMENTATION_OPTIONS = {
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          URL_ROOT:    '../',
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          VERSION:     '0.8.2',
 
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          VERSION:     '0.8.3',
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          COLLAPSE_MODINDEX: false,
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          FILE_SUFFIX: '.html'
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      };
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    </div>
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    <div id="docs-version-header">
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        Release: <span class="version-num">0.8.2</span> | Release Date: July 3, 2013
 
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        Release: <span class="version-num">0.8.3</span> | Release Date: October 26, 2013
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    </div>
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<div class="highlight-python"><div class="highlight"><pre><span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Employee</span><span class="p">)</span><span class="o">.</span><span class="n">with_polymorphic</span><span class="p">([</span><span class="n">Engineer</span><span class="p">,</span> <span class="n">Manager</span><span class="p">])</span><span class="o">.</span>\
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    <span class="nb">filter</span><span class="p">(</span><span class="n">or_</span><span class="p">(</span><span class="n">Engineer</span><span class="o">.</span><span class="n">engineer_info</span><span class="o">==</span><span class="s">&#39;w&#39;</span><span class="p">,</span> <span class="n">Manager</span><span class="o">.</span><span class="n">manager_data</span><span class="o">==</span><span class="s">&#39;q&#39;</span><span class="p">))</span></pre></div>
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</div>
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<p class="versionadded">
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<span class="versionmodified">New in version 0.8: </span><a class="reference internal" href="#sqlalchemy.orm.with_polymorphic" title="sqlalchemy.orm.with_polymorphic"><tt class="xref py py-func docutils literal"><span class="pre">orm.with_polymorphic()</span></tt></a>, an improved version of
 
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<p><span>New in version 0.8: </span><a class="reference internal" href="#sqlalchemy.orm.with_polymorphic" title="sqlalchemy.orm.with_polymorphic"><tt class="xref py py-func docutils literal"><span class="pre">orm.with_polymorphic()</span></tt></a>, an improved version of
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<a class="reference internal" href="query.html#sqlalchemy.orm.query.Query.with_polymorphic" title="sqlalchemy.orm.query.Query.with_polymorphic"><tt class="xref py py-meth docutils literal"><span class="pre">Query.with_polymorphic()</span></tt></a> method.</p>
 
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</div>
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<p>The mapper also accepts <tt class="docutils literal"><span class="pre">with_polymorphic</span></tt> as a configurational argument so
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that the joined-style load will be issued automatically. This argument may be
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the string <tt class="docutils literal"><span class="pre">'*'</span></tt>, a list of classes, or a tuple consisting of either,
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<tt class="descclassname">sqlalchemy.orm.</tt><tt class="descname">with_polymorphic</tt><big>(</big><em>base</em>, <em>classes</em>, <em>selectable=False</em>, <em>polymorphic_on=None</em>, <em>aliased=False</em>, <em>innerjoin=False</em>, <em>_use_mapper_path=False</em><big>)</big><a class="headerlink" href="#sqlalchemy.orm.with_polymorphic" title="Permalink to this definition">¶</a></dt>
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<dd><p>Produce an <a class="reference internal" href="query.html#sqlalchemy.orm.util.AliasedClass" title="sqlalchemy.orm.util.AliasedClass"><tt class="xref py py-class docutils literal"><span class="pre">AliasedClass</span></tt></a> construct which specifies
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columns for descendant mappers of the given base.</p>
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<p class="versionadded">
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<span class="versionmodified">New in version 0.8: </span><a class="reference internal" href="#sqlalchemy.orm.with_polymorphic" title="sqlalchemy.orm.with_polymorphic"><tt class="xref py py-func docutils literal"><span class="pre">orm.with_polymorphic()</span></tt></a> is in addition to the existing
 
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<p><span>New in version 0.8: </span><a class="reference internal" href="#sqlalchemy.orm.with_polymorphic" title="sqlalchemy.orm.with_polymorphic"><tt class="xref py py-func docutils literal"><span class="pre">orm.with_polymorphic()</span></tt></a> is in addition to the existing
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<a class="reference internal" href="query.html#sqlalchemy.orm.query.Query" title="sqlalchemy.orm.query.Query"><tt class="xref py py-class docutils literal"><span class="pre">Query</span></tt></a> method <a class="reference internal" href="query.html#sqlalchemy.orm.query.Query.with_polymorphic" title="sqlalchemy.orm.query.Query.with_polymorphic"><tt class="xref py py-meth docutils literal"><span class="pre">Query.with_polymorphic()</span></tt></a>,
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which has the same purpose but is not as flexible in its usage.</p>
 
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</div>
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<p>Using this method will ensure that each descendant mapper&#8217;s
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tables are included in the FROM clause, and will allow filter()
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criterion to be used against those tables.  The resulting
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simplistic scenarios.   However, direct control of table rendering
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is called for, such as the case when one wants to
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render to only the subclass table and not the parent table.</p>
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<p>This use case can be achieved by using the mapped <a class="reference internal" href="../core/schema.html#sqlalchemy.schema.Table" title="sqlalchemy.schema.Table"><tt class="xref py py-class docutils literal"><span class="pre">Table</span></tt></a>
 
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<p>This use case can be achieved by using the mapped <a class="reference internal" href="../core/metadata.html#sqlalchemy.schema.Table" title="sqlalchemy.schema.Table"><tt class="xref py py-class docutils literal"><span class="pre">Table</span></tt></a>
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objects directly.   For example, to
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query the name of employees with particular criterion:</p>
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<div class="highlight-python"><div class="highlight"><pre><span class="n">engineer</span> <span class="o">=</span> <span class="n">Engineer</span><span class="o">.</span><span class="n">__table__</span>
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<p>The EXISTS subquery above selects from the join of <tt class="docutils literal"><span class="pre">employees</span></tt> to
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<tt class="docutils literal"><span class="pre">engineers</span></tt>, and also specifies criterion which correlates the EXISTS
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subselect back to the parent <tt class="docutils literal"><span class="pre">companies</span></tt> table.</p>
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<p class="versionadded">
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<span class="versionmodified">New in version 0.8: </span><a class="reference internal" href="internals.html#sqlalchemy.orm.interfaces.PropComparator.of_type" title="sqlalchemy.orm.interfaces.PropComparator.of_type"><tt class="xref py py-func docutils literal"><span class="pre">of_type()</span></tt></a> accepts
 
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<p><span>New in version 0.8: </span><a class="reference internal" href="internals.html#sqlalchemy.orm.interfaces.PropComparator.of_type" title="sqlalchemy.orm.interfaces.PropComparator.of_type"><tt class="xref py py-func docutils literal"><span class="pre">of_type()</span></tt></a> accepts
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<a class="reference internal" href="query.html#sqlalchemy.orm.aliased" title="sqlalchemy.orm.aliased"><tt class="xref py py-func docutils literal"><span class="pre">orm.aliased()</span></tt></a> and <a class="reference internal" href="#sqlalchemy.orm.with_polymorphic" title="sqlalchemy.orm.with_polymorphic"><tt class="xref py py-func docutils literal"><span class="pre">orm.with_polymorphic()</span></tt></a> constructs in conjunction
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with <a class="reference internal" href="query.html#sqlalchemy.orm.query.Query.join" title="sqlalchemy.orm.query.Query.join"><tt class="xref py py-meth docutils literal"><span class="pre">Query.join()</span></tt></a>, <tt class="docutils literal"><span class="pre">any()</span></tt> and <tt class="docutils literal"><span class="pre">has()</span></tt>.</p>
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</div>
 
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</div>
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<div class="section" id="eager-loading-of-specific-subtypes">
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<h3>Eager Loading of Specific Subtypes<a class="headerlink" href="#eager-loading-of-specific-subtypes" title="Permalink to this headline">¶</a></h3>
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<p>The <a class="reference internal" href="loading.html#sqlalchemy.orm.joinedload" title="sqlalchemy.orm.joinedload"><tt class="xref py py-func docutils literal"><span class="pre">joinedload()</span></tt></a> and <a class="reference internal" href="loading.html#sqlalchemy.orm.subqueryload" title="sqlalchemy.orm.subqueryload"><tt class="xref py py-func docutils literal"><span class="pre">subqueryload()</span></tt></a> options also support
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    <span class="n">options</span><span class="p">(</span><span class="n">subqueryload_all</span><span class="p">(</span><span class="n">Company</span><span class="o">.</span><span class="n">employees</span><span class="o">.</span><span class="n">of_type</span><span class="p">(</span><span class="n">Engineer</span><span class="p">),</span>
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                    <span class="n">Engineer</span><span class="o">.</span><span class="n">machines</span><span class="p">))</span></pre></div>
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</div>
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<p class="versionadded">
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<span class="versionmodified">New in version 0.8: </span><a class="reference internal" href="loading.html#sqlalchemy.orm.joinedload" title="sqlalchemy.orm.joinedload"><tt class="xref py py-func docutils literal"><span class="pre">joinedload()</span></tt></a> and <a class="reference internal" href="loading.html#sqlalchemy.orm.subqueryload" title="sqlalchemy.orm.subqueryload"><tt class="xref py py-func docutils literal"><span class="pre">subqueryload()</span></tt></a> support
 
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<p><span>New in version 0.8: </span><a class="reference internal" href="loading.html#sqlalchemy.orm.joinedload" title="sqlalchemy.orm.joinedload"><tt class="xref py py-func docutils literal"><span class="pre">joinedload()</span></tt></a> and <a class="reference internal" href="loading.html#sqlalchemy.orm.subqueryload" title="sqlalchemy.orm.subqueryload"><tt class="xref py py-func docutils literal"><span class="pre">subqueryload()</span></tt></a> support
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paths that are qualified with
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<a class="reference internal" href="internals.html#sqlalchemy.orm.interfaces.PropComparator.of_type" title="sqlalchemy.orm.interfaces.PropComparator.of_type"><tt class="xref py py-func docutils literal"><span class="pre">of_type()</span></tt></a>.</p>
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</div>
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</div>
 
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</div>
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<div class="section" id="single-table-inheritance">
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<h2>Single Table Inheritance<a class="headerlink" href="#single-table-inheritance" title="Permalink to this headline">¶</a></h2>
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<p>Single table inheritance is where the attributes of the base class as well as
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</div>
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<div class="section" id="concrete-inheritance-with-declarative">
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<h3>Concrete Inheritance with Declarative<a class="headerlink" href="#concrete-inheritance-with-declarative" title="Permalink to this headline">¶</a></h3>
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<p class="versionadded">
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<span class="versionmodified">New in version 0.7.3: </span>The <a class="reference internal" href="extensions/declarative.html"><em>Declarative</em></a> module includes helpers for concrete
 
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<p><span>New in version 0.7.3: </span>The <a class="reference internal" href="extensions/declarative.html"><em>Declarative</em></a> module includes helpers for concrete
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inheritance. See <a class="reference internal" href="extensions/declarative.html#declarative-concrete-helpers"><em>Using the Concrete Helpers</em></a> for more information.</p>
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</div>
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</div>
 
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<div class="section" id="using-relationships-with-inheritance">
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<h2>Using Relationships with Inheritance<a class="headerlink" href="#using-relationships-with-inheritance" title="Permalink to this headline">¶</a></h2>
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<p>Both joined-table and single table inheritance scenarios produce mappings
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    <div id="docs-copyright">
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        &copy; <a href="../copyright.html">Copyright</a> 2007-2013, the SQLAlchemy authors and contributors.
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        Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3.
 
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        Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.2b1.
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    </div>
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</div>
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