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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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<h1>Source code for examples.versioned_history.history_meta</h1><div class="highlight"><pre>
<span></span><span class="sd">"""Versioned mixin class and other utilities."""</span>
<span class="kn">import</span> <span class="nn">datetime</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">Column</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">DateTime</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">event</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">ForeignKeyConstraint</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">Integer</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">Table</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="k">import</span> <span class="n">util</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.ext.declarative</span> <span class="k">import</span> <span class="n">declared_attr</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="k">import</span> <span class="n">attributes</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="k">import</span> <span class="n">mapper</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="k">import</span> <span class="n">object_mapper</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm.exc</span> <span class="k">import</span> <span class="n">UnmappedColumnError</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm.properties</span> <span class="k">import</span> <span class="n">RelationshipProperty</span>
<span class="k">def</span> <span class="nf">col_references_table</span><span class="p">(</span><span class="n">col</span><span class="p">,</span> <span class="n">table</span><span class="p">):</span>
<span class="k">for</span> <span class="n">fk</span> <span class="ow">in</span> <span class="n">col</span><span class="o">.</span><span class="n">foreign_keys</span><span class="p">:</span>
<span class="k">if</span> <span class="n">fk</span><span class="o">.</span><span class="n">references</span><span class="p">(</span><span class="n">table</span><span class="p">):</span>
<span class="k">return</span> <span class="kc">True</span>
<span class="k">return</span> <span class="kc">False</span>
<span class="k">def</span> <span class="nf">_is_versioning_col</span><span class="p">(</span><span class="n">col</span><span class="p">):</span>
<span class="k">return</span> <span class="s2">"version_meta"</span> <span class="ow">in</span> <span class="n">col</span><span class="o">.</span><span class="n">info</span>
<span class="k">def</span> <span class="nf">_history_mapper</span><span class="p">(</span><span class="n">local_mapper</span><span class="p">):</span>
<span class="bp">cls</span> <span class="o">=</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">class_</span>
<span class="c1"># set the "active_history" flag</span>
<span class="c1"># on on column-mapped attributes so that the old version</span>
<span class="c1"># of the info is always loaded (currently sets it on all attributes)</span>
<span class="k">for</span> <span class="n">prop</span> <span class="ow">in</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">iterate_properties</span><span class="p">:</span>
<span class="nb">getattr</span><span class="p">(</span><span class="n">local_mapper</span><span class="o">.</span><span class="n">class_</span><span class="p">,</span> <span class="n">prop</span><span class="o">.</span><span class="n">key</span><span class="p">)</span><span class="o">.</span><span class="n">impl</span><span class="o">.</span><span class="n">active_history</span> <span class="o">=</span> <span class="kc">True</span>
<span class="n">super_mapper</span> <span class="o">=</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">inherits</span>
<span class="n">super_history_mapper</span> <span class="o">=</span> <span class="nb">getattr</span><span class="p">(</span><span class="bp">cls</span><span class="p">,</span> <span class="s2">"__history_mapper__"</span><span class="p">,</span> <span class="kc">None</span><span class="p">)</span>
<span class="n">polymorphic_on</span> <span class="o">=</span> <span class="kc">None</span>
<span class="n">super_fks</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">def</span> <span class="nf">_col_copy</span><span class="p">(</span><span class="n">col</span><span class="p">):</span>
<span class="n">orig</span> <span class="o">=</span> <span class="n">col</span>
<span class="n">col</span> <span class="o">=</span> <span class="n">col</span><span class="o">.</span><span class="n">copy</span><span class="p">()</span>
<span class="n">orig</span><span class="o">.</span><span class="n">info</span><span class="p">[</span><span class="s2">"history_copy"</span><span class="p">]</span> <span class="o">=</span> <span class="n">col</span>
<span class="n">col</span><span class="o">.</span><span class="n">unique</span> <span class="o">=</span> <span class="kc">False</span>
<span class="n">col</span><span class="o">.</span><span class="n">default</span> <span class="o">=</span> <span class="n">col</span><span class="o">.</span><span class="n">server_default</span> <span class="o">=</span> <span class="kc">None</span>
<span class="n">col</span><span class="o">.</span><span class="n">autoincrement</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">return</span> <span class="n">col</span>
<span class="n">properties</span> <span class="o">=</span> <span class="n">util</span><span class="o">.</span><span class="n">OrderedDict</span><span class="p">()</span>
<span class="k">if</span> <span class="p">(</span>
<span class="ow">not</span> <span class="n">super_mapper</span>
<span class="ow">or</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">local_table</span> <span class="ow">is</span> <span class="ow">not</span> <span class="n">super_mapper</span><span class="o">.</span><span class="n">local_table</span>
<span class="p">):</span>
<span class="n">cols</span> <span class="o">=</span> <span class="p">[]</span>
<span class="n">version_meta</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"version_meta"</span><span class="p">:</span> <span class="kc">True</span><span class="p">}</span> <span class="c1"># add column.info to identify</span>
<span class="c1"># columns specific to versioning</span>
<span class="k">for</span> <span class="n">column</span> <span class="ow">in</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">c</span><span class="p">:</span>
<span class="k">if</span> <span class="n">_is_versioning_col</span><span class="p">(</span><span class="n">column</span><span class="p">):</span>
<span class="k">continue</span>
<span class="n">col</span> <span class="o">=</span> <span class="n">_col_copy</span><span class="p">(</span><span class="n">column</span><span class="p">)</span>
<span class="k">if</span> <span class="n">super_mapper</span> <span class="ow">and</span> <span class="n">col_references_table</span><span class="p">(</span>
<span class="n">column</span><span class="p">,</span> <span class="n">super_mapper</span><span class="o">.</span><span class="n">local_table</span>
<span class="p">):</span>
<span class="n">super_fks</span><span class="o">.</span><span class="n">append</span><span class="p">(</span>
<span class="p">(</span>
<span class="n">col</span><span class="o">.</span><span class="n">key</span><span class="p">,</span>
<span class="nb">list</span><span class="p">(</span><span class="n">super_history_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">primary_key</span><span class="p">)[</span><span class="mi">0</span><span class="p">],</span>
<span class="p">)</span>
<span class="p">)</span>
<span class="n">cols</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">col</span><span class="p">)</span>
<span class="k">if</span> <span class="n">column</span> <span class="ow">is</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">polymorphic_on</span><span class="p">:</span>
<span class="n">polymorphic_on</span> <span class="o">=</span> <span class="n">col</span>
<span class="n">orig_prop</span> <span class="o">=</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">get_property_by_column</span><span class="p">(</span><span class="n">column</span><span class="p">)</span>
<span class="c1"># carry over column re-mappings</span>
<span class="k">if</span> <span class="p">(</span>
<span class="nb">len</span><span class="p">(</span><span class="n">orig_prop</span><span class="o">.</span><span class="n">columns</span><span class="p">)</span> <span class="o">></span> <span class="mi">1</span>
<span class="ow">or</span> <span class="n">orig_prop</span><span class="o">.</span><span class="n">columns</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">key</span> <span class="o">!=</span> <span class="n">orig_prop</span><span class="o">.</span><span class="n">key</span>
<span class="p">):</span>
<span class="n">properties</span><span class="p">[</span><span class="n">orig_prop</span><span class="o">.</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="nb">tuple</span><span class="p">(</span>
<span class="n">col</span><span class="o">.</span><span class="n">info</span><span class="p">[</span><span class="s2">"history_copy"</span><span class="p">]</span> <span class="k">for</span> <span class="n">col</span> <span class="ow">in</span> <span class="n">orig_prop</span><span class="o">.</span><span class="n">columns</span>
<span class="p">)</span>
<span class="k">if</span> <span class="n">super_mapper</span><span class="p">:</span>
<span class="n">super_fks</span><span class="o">.</span><span class="n">append</span><span class="p">(</span>
<span class="p">(</span><span class="s2">"version"</span><span class="p">,</span> <span class="n">super_history_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">version</span><span class="p">)</span>
<span class="p">)</span>
<span class="c1"># "version" stores the integer version id. This column is</span>
<span class="c1"># required.</span>
<span class="n">cols</span><span class="o">.</span><span class="n">append</span><span class="p">(</span>
<span class="n">Column</span><span class="p">(</span>
<span class="s2">"version"</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="kc">True</span><span class="p">,</span>
<span class="n">autoincrement</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
<span class="n">info</span><span class="o">=</span><span class="n">version_meta</span><span class="p">,</span>
<span class="p">)</span>
<span class="p">)</span>
<span class="c1"># "changed" column stores the UTC timestamp of when the</span>
<span class="c1"># history row was created.</span>
<span class="c1"># This column is optional and can be omitted.</span>
<span class="n">cols</span><span class="o">.</span><span class="n">append</span><span class="p">(</span>
<span class="n">Column</span><span class="p">(</span>
<span class="s2">"changed"</span><span class="p">,</span>
<span class="n">DateTime</span><span class="p">,</span>
<span class="n">default</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">datetime</span><span class="o">.</span><span class="n">utcnow</span><span class="p">,</span>
<span class="n">info</span><span class="o">=</span><span class="n">version_meta</span><span class="p">,</span>
<span class="p">)</span>
<span class="p">)</span>
<span class="k">if</span> <span class="n">super_fks</span><span class="p">:</span>
<span class="n">cols</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">ForeignKeyConstraint</span><span class="p">(</span><span class="o">*</span><span class="nb">zip</span><span class="p">(</span><span class="o">*</span><span class="n">super_fks</span><span class="p">)))</span>
<span class="n">table</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span>
<span class="n">local_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">name</span> <span class="o">+</span> <span class="s2">"_history"</span><span class="p">,</span>
<span class="n">local_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">metadata</span><span class="p">,</span>
<span class="o">*</span><span class="n">cols</span><span class="p">,</span>
<span class="n">schema</span><span class="o">=</span><span class="n">local_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">schema</span>
<span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="c1"># single table inheritance. take any additional columns that may have</span>
<span class="c1"># been added and add them to the history table.</span>
<span class="k">for</span> <span class="n">column</span> <span class="ow">in</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">c</span><span class="p">:</span>
<span class="k">if</span> <span class="n">column</span><span class="o">.</span><span class="n">key</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">super_history_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">c</span><span class="p">:</span>
<span class="n">col</span> <span class="o">=</span> <span class="n">_col_copy</span><span class="p">(</span><span class="n">column</span><span class="p">)</span>
<span class="n">super_history_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">append_column</span><span class="p">(</span><span class="n">col</span><span class="p">)</span>
<span class="n">table</span> <span class="o">=</span> <span class="kc">None</span>
<span class="k">if</span> <span class="n">super_history_mapper</span><span class="p">:</span>
<span class="n">bases</span> <span class="o">=</span> <span class="p">(</span><span class="n">super_history_mapper</span><span class="o">.</span><span class="n">class_</span><span class="p">,)</span>
<span class="k">if</span> <span class="n">table</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">properties</span><span class="p">[</span><span class="s2">"changed"</span><span class="p">]</span> <span class="o">=</span> <span class="p">(</span><span class="n">table</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">changed</span><span class="p">,)</span> <span class="o">+</span> <span class="nb">tuple</span><span class="p">(</span>
<span class="n">super_history_mapper</span><span class="o">.</span><span class="n">attrs</span><span class="o">.</span><span class="n">changed</span><span class="o">.</span><span class="n">columns</span>
<span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">bases</span> <span class="o">=</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">base_mapper</span><span class="o">.</span><span class="n">class_</span><span class="o">.</span><span class="vm">__bases__</span>
<span class="n">versioned_cls</span> <span class="o">=</span> <span class="nb">type</span><span class="o">.</span><span class="fm">__new__</span><span class="p">(</span><span class="nb">type</span><span class="p">,</span> <span class="s2">"</span><span class="si">%s</span><span class="s2">History"</span> <span class="o">%</span> <span class="bp">cls</span><span class="o">.</span><span class="vm">__name__</span><span class="p">,</span> <span class="n">bases</span><span class="p">,</span> <span class="p">{})</span>
<span class="n">m</span> <span class="o">=</span> <span class="n">mapper</span><span class="p">(</span>
<span class="n">versioned_cls</span><span class="p">,</span>
<span class="n">table</span><span class="p">,</span>
<span class="n">inherits</span><span class="o">=</span><span class="n">super_history_mapper</span><span class="p">,</span>
<span class="n">polymorphic_on</span><span class="o">=</span><span class="n">polymorphic_on</span><span class="p">,</span>
<span class="n">polymorphic_identity</span><span class="o">=</span><span class="n">local_mapper</span><span class="o">.</span><span class="n">polymorphic_identity</span><span class="p">,</span>
<span class="n">properties</span><span class="o">=</span><span class="n">properties</span><span class="p">,</span>
<span class="p">)</span>
<span class="bp">cls</span><span class="o">.</span><span class="n">__history_mapper__</span> <span class="o">=</span> <span class="n">m</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">super_history_mapper</span><span class="p">:</span>
<span class="n">local_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">append_column</span><span class="p">(</span>
<span class="n">Column</span><span class="p">(</span><span class="s2">"version"</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">nullable</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
<span class="p">)</span>
<span class="n">local_mapper</span><span class="o">.</span><span class="n">add_property</span><span class="p">(</span>
<span class="s2">"version"</span><span class="p">,</span> <span class="n">local_mapper</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">version</span>
<span class="p">)</span>
<span class="k">class</span> <span class="nc">Versioned</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="nd">@declared_attr</span>
<span class="k">def</span> <span class="nf">__mapper_cls__</span><span class="p">(</span><span class="bp">cls</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">map_</span><span class="p">(</span><span class="bp">cls</span><span class="p">,</span> <span class="o">*</span><span class="n">arg</span><span class="p">,</span> <span class="o">**</span><span class="n">kw</span><span class="p">):</span>
<span class="n">mp</span> <span class="o">=</span> <span class="n">mapper</span><span class="p">(</span><span class="bp">cls</span><span class="p">,</span> <span class="o">*</span><span class="n">arg</span><span class="p">,</span> <span class="o">**</span><span class="n">kw</span><span class="p">)</span>
<span class="n">_history_mapper</span><span class="p">(</span><span class="n">mp</span><span class="p">)</span>
<span class="k">return</span> <span class="n">mp</span>
<span class="k">return</span> <span class="n">map_</span>
<span class="n">__table_args__</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"sqlite_autoincrement"</span><span class="p">:</span> <span class="kc">True</span><span class="p">}</span>
<span class="sd">"""Use sqlite_autoincrement, to ensure unique integer values</span>
<span class="sd"> are used for new rows even for rows taht have been deleted."""</span>
<span class="k">def</span> <span class="nf">versioned_objects</span><span class="p">(</span><span class="n">iter_</span><span class="p">):</span>
<span class="k">for</span> <span class="n">obj</span> <span class="ow">in</span> <span class="n">iter_</span><span class="p">:</span>
<span class="k">if</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="s2">"__history_mapper__"</span><span class="p">):</span>
<span class="k">yield</span> <span class="n">obj</span>
<span class="k">def</span> <span class="nf">create_version</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">session</span><span class="p">,</span> <span class="n">deleted</span><span class="o">=</span><span class="kc">False</span><span class="p">):</span>
<span class="n">obj_mapper</span> <span class="o">=</span> <span class="n">object_mapper</span><span class="p">(</span><span class="n">obj</span><span class="p">)</span>
<span class="n">history_mapper</span> <span class="o">=</span> <span class="n">obj</span><span class="o">.</span><span class="n">__history_mapper__</span>
<span class="n">history_cls</span> <span class="o">=</span> <span class="n">history_mapper</span><span class="o">.</span><span class="n">class_</span>
<span class="n">obj_state</span> <span class="o">=</span> <span class="n">attributes</span><span class="o">.</span><span class="n">instance_state</span><span class="p">(</span><span class="n">obj</span><span class="p">)</span>
<span class="n">attr</span> <span class="o">=</span> <span class="p">{}</span>
<span class="n">obj_changed</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">for</span> <span class="n">om</span><span class="p">,</span> <span class="n">hm</span> <span class="ow">in</span> <span class="nb">zip</span><span class="p">(</span>
<span class="n">obj_mapper</span><span class="o">.</span><span class="n">iterate_to_root</span><span class="p">(),</span> <span class="n">history_mapper</span><span class="o">.</span><span class="n">iterate_to_root</span><span class="p">()</span>
<span class="p">):</span>
<span class="k">if</span> <span class="n">hm</span><span class="o">.</span><span class="n">single</span><span class="p">:</span>
<span class="k">continue</span>
<span class="k">for</span> <span class="n">hist_col</span> <span class="ow">in</span> <span class="n">hm</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">c</span><span class="p">:</span>
<span class="k">if</span> <span class="n">_is_versioning_col</span><span class="p">(</span><span class="n">hist_col</span><span class="p">):</span>
<span class="k">continue</span>
<span class="n">obj_col</span> <span class="o">=</span> <span class="n">om</span><span class="o">.</span><span class="n">local_table</span><span class="o">.</span><span class="n">c</span><span class="p">[</span><span class="n">hist_col</span><span class="o">.</span><span class="n">key</span><span class="p">]</span>
<span class="c1"># get the value of the</span>
<span class="c1"># attribute based on the MapperProperty related to the</span>
<span class="c1"># mapped column. this will allow usage of MapperProperties</span>
<span class="c1"># that have a different keyname than that of the mapped column.</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">prop</span> <span class="o">=</span> <span class="n">obj_mapper</span><span class="o">.</span><span class="n">get_property_by_column</span><span class="p">(</span><span class="n">obj_col</span><span class="p">)</span>
<span class="k">except</span> <span class="n">UnmappedColumnError</span><span class="p">:</span>
<span class="c1"># in the case of single table inheritance, there may be</span>
<span class="c1"># columns on the mapped table intended for the subclass only.</span>
<span class="c1"># the "unmapped" status of the subclass column on the</span>
<span class="c1"># base class is a feature of the declarative module.</span>
<span class="k">continue</span>
<span class="c1"># expired object attributes and also deferred cols might not</span>
<span class="c1"># be in the dict. force it to load no matter what by</span>
<span class="c1"># using getattr().</span>
<span class="k">if</span> <span class="n">prop</span><span class="o">.</span><span class="n">key</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">obj_state</span><span class="o">.</span><span class="n">dict</span><span class="p">:</span>
<span class="nb">getattr</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">prop</span><span class="o">.</span><span class="n">key</span><span class="p">)</span>
<span class="n">a</span><span class="p">,</span> <span class="n">u</span><span class="p">,</span> <span class="n">d</span> <span class="o">=</span> <span class="n">attributes</span><span class="o">.</span><span class="n">get_history</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">prop</span><span class="o">.</span><span class="n">key</span><span class="p">)</span>
<span class="k">if</span> <span class="n">d</span><span class="p">:</span>
<span class="n">attr</span><span class="p">[</span><span class="n">prop</span><span class="o">.</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="n">d</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="n">obj_changed</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">elif</span> <span class="n">u</span><span class="p">:</span>
<span class="n">attr</span><span class="p">[</span><span class="n">prop</span><span class="o">.</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="n">u</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="k">elif</span> <span class="n">a</span><span class="p">:</span>
<span class="c1"># if the attribute had no value.</span>
<span class="n">attr</span><span class="p">[</span><span class="n">prop</span><span class="o">.</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="n">a</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="n">obj_changed</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">obj_changed</span><span class="p">:</span>
<span class="c1"># not changed, but we have relationships. OK</span>
<span class="c1"># check those too</span>
<span class="k">for</span> <span class="n">prop</span> <span class="ow">in</span> <span class="n">obj_mapper</span><span class="o">.</span><span class="n">iterate_properties</span><span class="p">:</span>
<span class="k">if</span> <span class="p">(</span>
<span class="nb">isinstance</span><span class="p">(</span><span class="n">prop</span><span class="p">,</span> <span class="n">RelationshipProperty</span><span class="p">)</span>
<span class="ow">and</span> <span class="n">attributes</span><span class="o">.</span><span class="n">get_history</span><span class="p">(</span>
<span class="n">obj</span><span class="p">,</span> <span class="n">prop</span><span class="o">.</span><span class="n">key</span><span class="p">,</span> <span class="n">passive</span><span class="o">=</span><span class="n">attributes</span><span class="o">.</span><span class="n">PASSIVE_NO_INITIALIZE</span>
<span class="p">)</span><span class="o">.</span><span class="n">has_changes</span><span class="p">()</span>
<span class="p">):</span>
<span class="k">for</span> <span class="n">p</span> <span class="ow">in</span> <span class="n">prop</span><span class="o">.</span><span class="n">local_columns</span><span class="p">:</span>
<span class="k">if</span> <span class="n">p</span><span class="o">.</span><span class="n">foreign_keys</span><span class="p">:</span>
<span class="n">obj_changed</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">break</span>
<span class="k">if</span> <span class="n">obj_changed</span> <span class="ow">is</span> <span class="kc">True</span><span class="p">:</span>
<span class="k">break</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">obj_changed</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">deleted</span><span class="p">:</span>
<span class="k">return</span>
<span class="n">attr</span><span class="p">[</span><span class="s2">"version"</span><span class="p">]</span> <span class="o">=</span> <span class="n">obj</span><span class="o">.</span><span class="n">version</span>
<span class="n">hist</span> <span class="o">=</span> <span class="n">history_cls</span><span class="p">()</span>
<span class="k">for</span> <span class="n">key</span><span class="p">,</span> <span class="n">value</span> <span class="ow">in</span> <span class="n">attr</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
<span class="nb">setattr</span><span class="p">(</span><span class="n">hist</span><span class="p">,</span> <span class="n">key</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span>
<span class="n">session</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">hist</span><span class="p">)</span>
<span class="n">obj</span><span class="o">.</span><span class="n">version</span> <span class="o">+=</span> <span class="mi">1</span>
<span class="k">def</span> <span class="nf">versioned_session</span><span class="p">(</span><span class="n">session</span><span class="p">):</span>
<span class="nd">@event</span><span class="o">.</span><span class="n">listens_for</span><span class="p">(</span><span class="n">session</span><span class="p">,</span> <span class="s2">"before_flush"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">before_flush</span><span class="p">(</span><span class="n">session</span><span class="p">,</span> <span class="n">flush_context</span><span class="p">,</span> <span class="n">instances</span><span class="p">):</span>
<span class="k">for</span> <span class="n">obj</span> <span class="ow">in</span> <span class="n">versioned_objects</span><span class="p">(</span><span class="n">session</span><span class="o">.</span><span class="n">dirty</span><span class="p">):</span>
<span class="n">create_version</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">session</span><span class="p">)</span>
<span class="k">for</span> <span class="n">obj</span> <span class="ow">in</span> <span class="n">versioned_objects</span><span class="p">(</span><span class="n">session</span><span class="o">.</span><span class="n">deleted</span><span class="p">):</span>
<span class="n">create_version</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">session</span><span class="p">,</span> <span class="n">deleted</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span></pre></div>
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