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Release: <span class="version-num">0.9.8</span> | Release Date: October 13, 2014
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<h1>SQLAlchemy 0.9 Documentation</h1>
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<h1>Source code for examples.large_collection.large_collection</h1><div class="highlight"><pre>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</span> <span class="p">(</span><span class="n">MetaData</span><span class="p">,</span> <span class="n">Table</span><span class="p">,</span> <span class="n">Column</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">String</span><span class="p">,</span> <span class="n">ForeignKey</span><span class="p">,</span>
<span class="n">create_engine</span><span class="p">)</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="kn">import</span> <span class="p">(</span><span class="n">mapper</span><span class="p">,</span> <span class="n">relationship</span><span class="p">,</span> <span class="n">sessionmaker</span><span class="p">)</span>
<span class="n">meta</span> <span class="o">=</span> <span class="n">MetaData</span><span class="p">()</span>
<span class="n">org_table</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s">'organizations'</span><span class="p">,</span> <span class="n">meta</span><span class="p">,</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'org_id'</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">),</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'org_name'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">50</span><span class="p">),</span> <span class="n">nullable</span><span class="o">=</span><span class="bp">False</span><span class="p">,</span> <span class="n">key</span><span class="o">=</span><span class="s">'name'</span><span class="p">),</span>
<span class="n">mysql_engine</span><span class="o">=</span><span class="s">'InnoDB'</span><span class="p">)</span>
<span class="n">member_table</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s">'members'</span><span class="p">,</span> <span class="n">meta</span><span class="p">,</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'member_id'</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">),</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'member_name'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">50</span><span class="p">),</span> <span class="n">nullable</span><span class="o">=</span><span class="bp">False</span><span class="p">,</span> <span class="n">key</span><span class="o">=</span><span class="s">'name'</span><span class="p">),</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'org_id'</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span>
<span class="n">ForeignKey</span><span class="p">(</span><span class="s">'organizations.org_id'</span><span class="p">,</span> <span class="n">ondelete</span><span class="o">=</span><span class="s">"CASCADE"</span><span class="p">)),</span>
<span class="n">mysql_engine</span><span class="o">=</span><span class="s">'InnoDB'</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Organization</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="n">name</span>
<span class="k">class</span> <span class="nc">Member</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="n">name</span>
<span class="n">mapper</span><span class="p">(</span><span class="n">Organization</span><span class="p">,</span> <span class="n">org_table</span><span class="p">,</span> <span class="n">properties</span> <span class="o">=</span> <span class="p">{</span>
<span class="s">'members'</span> <span class="p">:</span> <span class="n">relationship</span><span class="p">(</span><span class="n">Member</span><span class="p">,</span>
<span class="c"># Organization.members will be a Query object - no loading</span>
<span class="c"># of the entire collection occurs unless requested</span>
<span class="n">lazy</span><span class="o">=</span><span class="s">"dynamic"</span><span class="p">,</span>
<span class="c"># Member objects "belong" to their parent, are deleted when</span>
<span class="c"># removed from the collection</span>
<span class="n">cascade</span><span class="o">=</span><span class="s">"all, delete-orphan"</span><span class="p">,</span>
<span class="c"># "delete, delete-orphan" cascade does not load in objects on delete,</span>
<span class="c"># allows ON DELETE CASCADE to handle it.</span>
<span class="c"># this only works with a database that supports ON DELETE CASCADE -</span>
<span class="c"># *not* sqlite or MySQL with MyISAM</span>
<span class="n">passive_deletes</span><span class="o">=</span><span class="bp">True</span><span class="p">,</span>
<span class="p">)</span>
<span class="p">})</span>
<span class="n">mapper</span><span class="p">(</span><span class="n">Member</span><span class="p">,</span> <span class="n">member_table</span><span class="p">)</span>
<span class="k">if</span> <span class="n">__name__</span> <span class="o">==</span> <span class="s">'__main__'</span><span class="p">:</span>
<span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">"postgresql://scott:tiger@localhost/test"</span><span class="p">,</span> <span class="n">echo</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">meta</span><span class="o">.</span><span class="n">create_all</span><span class="p">(</span><span class="n">engine</span><span class="p">)</span>
<span class="c"># expire_on_commit=False means the session contents</span>
<span class="c"># will not get invalidated after commit.</span>
<span class="n">sess</span> <span class="o">=</span> <span class="n">sessionmaker</span><span class="p">(</span><span class="n">engine</span><span class="p">,</span> <span class="n">expire_on_commit</span><span class="o">=</span><span class="bp">False</span><span class="p">)()</span>
<span class="c"># create org with some members</span>
<span class="n">org</span> <span class="o">=</span> <span class="n">Organization</span><span class="p">(</span><span class="s">'org one'</span><span class="p">)</span>
<span class="n">org</span><span class="o">.</span><span class="n">members</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Member</span><span class="p">(</span><span class="s">'member one'</span><span class="p">))</span>
<span class="n">org</span><span class="o">.</span><span class="n">members</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Member</span><span class="p">(</span><span class="s">'member two'</span><span class="p">))</span>
<span class="n">org</span><span class="o">.</span><span class="n">members</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Member</span><span class="p">(</span><span class="s">'member three'</span><span class="p">))</span>
<span class="n">sess</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">org</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">"-------------------------</span><span class="se">\n</span><span class="s">flush one - save org + 3 members</span><span class="se">\n</span><span class="s">"</span><span class="p">)</span>
<span class="n">sess</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="c"># the 'members' collection is a Query. it issues</span>
<span class="c"># SQL as needed to load subsets of the collection.</span>
<span class="k">print</span><span class="p">(</span><span class="s">"-------------------------</span><span class="se">\n</span><span class="s">load subset of members</span><span class="se">\n</span><span class="s">"</span><span class="p">)</span>
<span class="n">members</span> <span class="o">=</span> <span class="n">org</span><span class="o">.</span><span class="n">members</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">member_table</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">name</span><span class="o">.</span><span class="n">like</span><span class="p">(</span><span class="s">'%member t%'</span><span class="p">))</span><span class="o">.</span><span class="n">all</span><span class="p">()</span>
<span class="k">print</span><span class="p">(</span><span class="n">members</span><span class="p">)</span>
<span class="c"># new Members can be appended without any</span>
<span class="c"># SQL being emitted to load the full collection</span>
<span class="n">org</span><span class="o">.</span><span class="n">members</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Member</span><span class="p">(</span><span class="s">'member four'</span><span class="p">))</span>
<span class="n">org</span><span class="o">.</span><span class="n">members</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Member</span><span class="p">(</span><span class="s">'member five'</span><span class="p">))</span>
<span class="n">org</span><span class="o">.</span><span class="n">members</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">Member</span><span class="p">(</span><span class="s">'member six'</span><span class="p">))</span>
<span class="k">print</span><span class="p">(</span><span class="s">"-------------------------</span><span class="se">\n</span><span class="s">flush two - save 3 more members</span><span class="se">\n</span><span class="s">"</span><span class="p">)</span>
<span class="n">sess</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="c"># delete the object. Using ON DELETE CASCADE</span>
<span class="c"># SQL is only emitted for the head row - the Member rows</span>
<span class="c"># disappear automatically without the need for additional SQL.</span>
<span class="n">sess</span><span class="o">.</span><span class="n">delete</span><span class="p">(</span><span class="n">org</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">"-------------------------</span><span class="se">\n</span><span class="s">flush three - delete org, delete members in one statement</span><span class="se">\n</span><span class="s">"</span><span class="p">)</span>
<span class="n">sess</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="k">print</span><span class="p">(</span><span class="s">"-------------------------</span><span class="se">\n</span><span class="s">no Member rows should remain:</span><span class="se">\n</span><span class="s">"</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="n">sess</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Member</span><span class="p">)</span><span class="o">.</span><span class="n">count</span><span class="p">())</span>
<span class="n">sess</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="k">print</span><span class="p">(</span><span class="s">"------------------------</span><span class="se">\n</span><span class="s">done. dropping tables."</span><span class="p">)</span>
<span class="n">meta</span><span class="o">.</span><span class="n">drop_all</span><span class="p">(</span><span class="n">engine</span><span class="p">)</span></pre></div>
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