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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.postgis.postgis</h1><div class="highlight"><pre>
<span class="kn">from</span> <span class="nn">sqlalchemy.types</span> <span class="kn">import</span> <span class="n">UserDefinedType</span><span class="p">,</span> <span class="n">_Binary</span><span class="p">,</span> <span class="n">TypeDecorator</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.sql</span> <span class="kn">import</span> <span class="n">expression</span><span class="p">,</span> <span class="n">type_coerce</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</span> <span class="n">event</span><span class="p">,</span> <span class="n">Table</span>
<span class="kn">import</span> <span class="nn">binascii</span>
<span class="c"># Python datatypes</span>
<span class="k">class</span> <span class="nc">GisElement</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="sd">"""Represents a geometry value."""</span>
<span class="k">def</span> <span class="nf">__str__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">desc</span>
<span class="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="s">"<</span><span class="si">%s</span><span class="s"> at 0x</span><span class="si">%x</span><span class="s">; </span><span class="si">%r</span><span class="s">>"</span> <span class="o">%</span> <span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">__class__</span><span class="o">.</span><span class="n">__name__</span><span class="p">,</span>
<span class="nb">id</span><span class="p">(</span><span class="bp">self</span><span class="p">),</span> <span class="bp">self</span><span class="o">.</span><span class="n">desc</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">BinaryGisElement</span><span class="p">(</span><span class="n">GisElement</span><span class="p">,</span> <span class="n">expression</span><span class="o">.</span><span class="n">Function</span><span class="p">):</span>
<span class="sd">"""Represents a Geometry value expressed as binary."""</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">data</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">data</span> <span class="o">=</span> <span class="n">data</span>
<span class="n">expression</span><span class="o">.</span><span class="n">Function</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="s">"ST_GeomFromEWKB"</span><span class="p">,</span> <span class="n">data</span><span class="p">,</span>
<span class="n">type_</span><span class="o">=</span><span class="n">Geometry</span><span class="p">(</span><span class="n">coerce_</span><span class="o">=</span><span class="s">"binary"</span><span class="p">))</span>
<span class="nd">@property</span>
<span class="k">def</span> <span class="nf">desc</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">as_hex</span>
<span class="nd">@property</span>
<span class="k">def</span> <span class="nf">as_hex</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="n">binascii</span><span class="o">.</span><span class="n">hexlify</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">data</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">TextualGisElement</span><span class="p">(</span><span class="n">GisElement</span><span class="p">,</span> <span class="n">expression</span><span class="o">.</span><span class="n">Function</span><span class="p">):</span>
<span class="sd">"""Represents a Geometry value expressed as text."""</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">desc</span><span class="p">,</span> <span class="n">srid</span><span class="o">=-</span><span class="mi">1</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">desc</span> <span class="o">=</span> <span class="n">desc</span>
<span class="n">expression</span><span class="o">.</span><span class="n">Function</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="s">"ST_GeomFromText"</span><span class="p">,</span> <span class="n">desc</span><span class="p">,</span> <span class="n">srid</span><span class="p">,</span>
<span class="n">type_</span><span class="o">=</span><span class="n">Geometry</span><span class="p">)</span>
<span class="c"># SQL datatypes.</span>
<span class="k">class</span> <span class="nc">Geometry</span><span class="p">(</span><span class="n">UserDefinedType</span><span class="p">):</span>
<span class="sd">"""Base PostGIS Geometry column type."""</span>
<span class="n">name</span> <span class="o">=</span> <span class="s">"GEOMETRY"</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">dimension</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">srid</span><span class="o">=-</span><span class="mi">1</span><span class="p">,</span>
<span class="n">coerce_</span><span class="o">=</span><span class="s">"text"</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">dimension</span> <span class="o">=</span> <span class="n">dimension</span>
<span class="bp">self</span><span class="o">.</span><span class="n">srid</span> <span class="o">=</span> <span class="n">srid</span>
<span class="bp">self</span><span class="o">.</span><span class="n">coerce</span> <span class="o">=</span> <span class="n">coerce_</span>
<span class="k">class</span> <span class="nc">comparator_factory</span><span class="p">(</span><span class="n">UserDefinedType</span><span class="o">.</span><span class="n">Comparator</span><span class="p">):</span>
<span class="sd">"""Define custom operations for geometry types."""</span>
<span class="c"># override the __eq__() operator</span>
<span class="k">def</span> <span class="nf">__eq__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">other</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">op</span><span class="p">(</span><span class="s">'~='</span><span class="p">)(</span><span class="n">other</span><span class="p">)</span>
<span class="c"># add a custom operator</span>
<span class="k">def</span> <span class="nf">intersects</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">other</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">op</span><span class="p">(</span><span class="s">'&&'</span><span class="p">)(</span><span class="n">other</span><span class="p">)</span>
<span class="c"># any number of GIS operators can be overridden/added here</span>
<span class="c"># using the techniques above.</span>
<span class="k">def</span> <span class="nf">_coerce_compared_value</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">op</span><span class="p">,</span> <span class="n">value</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span>
<span class="k">def</span> <span class="nf">get_col_spec</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span>
<span class="k">def</span> <span class="nf">bind_expression</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">bindvalue</span><span class="p">):</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">coerce</span> <span class="o">==</span> <span class="s">"text"</span><span class="p">:</span>
<span class="k">return</span> <span class="n">TextualGisElement</span><span class="p">(</span><span class="n">bindvalue</span><span class="p">)</span>
<span class="k">elif</span> <span class="bp">self</span><span class="o">.</span><span class="n">coerce</span> <span class="o">==</span> <span class="s">"binary"</span><span class="p">:</span>
<span class="k">return</span> <span class="n">BinaryGisElement</span><span class="p">(</span><span class="n">bindvalue</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">assert</span> <span class="bp">False</span>
<span class="k">def</span> <span class="nf">column_expression</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">col</span><span class="p">):</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">coerce</span> <span class="o">==</span> <span class="s">"text"</span><span class="p">:</span>
<span class="k">return</span> <span class="n">func</span><span class="o">.</span><span class="n">ST_AsText</span><span class="p">(</span><span class="n">col</span><span class="p">,</span> <span class="n">type_</span><span class="o">=</span><span class="bp">self</span><span class="p">)</span>
<span class="k">elif</span> <span class="bp">self</span><span class="o">.</span><span class="n">coerce</span> <span class="o">==</span> <span class="s">"binary"</span><span class="p">:</span>
<span class="k">return</span> <span class="n">func</span><span class="o">.</span><span class="n">ST_AsBinary</span><span class="p">(</span><span class="n">col</span><span class="p">,</span> <span class="n">type_</span><span class="o">=</span><span class="bp">self</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">assert</span> <span class="bp">False</span>
<span class="k">def</span> <span class="nf">bind_processor</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">dialect</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">process</span><span class="p">(</span><span class="n">value</span><span class="p">):</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="n">GisElement</span><span class="p">):</span>
<span class="k">return</span> <span class="n">value</span><span class="o">.</span><span class="n">desc</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">return</span> <span class="n">value</span>
<span class="k">return</span> <span class="n">process</span>
<span class="k">def</span> <span class="nf">result_processor</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">dialect</span><span class="p">,</span> <span class="n">coltype</span><span class="p">):</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">coerce</span> <span class="o">==</span> <span class="s">"text"</span><span class="p">:</span>
<span class="n">fac</span> <span class="o">=</span> <span class="n">TextualGisElement</span>
<span class="k">elif</span> <span class="bp">self</span><span class="o">.</span><span class="n">coerce</span> <span class="o">==</span> <span class="s">"binary"</span><span class="p">:</span>
<span class="n">fac</span> <span class="o">=</span> <span class="n">BinaryGisElement</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">assert</span> <span class="bp">False</span>
<span class="k">def</span> <span class="nf">process</span><span class="p">(</span><span class="n">value</span><span class="p">):</span>
<span class="k">if</span> <span class="n">value</span> <span class="ow">is</span> <span class="ow">not</span> <span class="bp">None</span><span class="p">:</span>
<span class="k">return</span> <span class="n">fac</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">return</span> <span class="n">value</span>
<span class="k">return</span> <span class="n">process</span>
<span class="k">def</span> <span class="nf">adapt</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">impltype</span><span class="p">):</span>
<span class="k">return</span> <span class="n">impltype</span><span class="p">(</span><span class="n">dimension</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">dimension</span><span class="p">,</span>
<span class="n">srid</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">srid</span><span class="p">,</span> <span class="n">coerce_</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">coerce</span><span class="p">)</span>
<span class="c"># other datatypes can be added as needed.</span>
<span class="k">class</span> <span class="nc">Point</span><span class="p">(</span><span class="n">Geometry</span><span class="p">):</span>
<span class="n">name</span> <span class="o">=</span> <span class="s">'POINT'</span>
<span class="k">class</span> <span class="nc">Curve</span><span class="p">(</span><span class="n">Geometry</span><span class="p">):</span>
<span class="n">name</span> <span class="o">=</span> <span class="s">'CURVE'</span>
<span class="k">class</span> <span class="nc">LineString</span><span class="p">(</span><span class="n">Curve</span><span class="p">):</span>
<span class="n">name</span> <span class="o">=</span> <span class="s">'LINESTRING'</span>
<span class="c"># ... etc.</span>
<span class="c"># DDL integration</span>
<span class="c"># Postgis historically has required AddGeometryColumn/DropGeometryColumn</span>
<span class="c"># and other management methods in order to create Postgis columns. Newer</span>
<span class="c"># versions don't appear to require these special steps anymore. However,</span>
<span class="c"># here we illustrate how to set up these features in any case.</span>
<span class="k">def</span> <span class="nf">setup_ddl_events</span><span class="p">():</span>
<span class="nd">@event.listens_for</span><span class="p">(</span><span class="n">Table</span><span class="p">,</span> <span class="s">"before_create"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">before_create</span><span class="p">(</span><span class="n">target</span><span class="p">,</span> <span class="n">connection</span><span class="p">,</span> <span class="o">**</span><span class="n">kw</span><span class="p">):</span>
<span class="n">dispatch</span><span class="p">(</span><span class="s">"before-create"</span><span class="p">,</span> <span class="n">target</span><span class="p">,</span> <span class="n">connection</span><span class="p">)</span>
<span class="nd">@event.listens_for</span><span class="p">(</span><span class="n">Table</span><span class="p">,</span> <span class="s">"after_create"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">after_create</span><span class="p">(</span><span class="n">target</span><span class="p">,</span> <span class="n">connection</span><span class="p">,</span> <span class="o">**</span><span class="n">kw</span><span class="p">):</span>
<span class="n">dispatch</span><span class="p">(</span><span class="s">"after-create"</span><span class="p">,</span> <span class="n">target</span><span class="p">,</span> <span class="n">connection</span><span class="p">)</span>
<span class="nd">@event.listens_for</span><span class="p">(</span><span class="n">Table</span><span class="p">,</span> <span class="s">"before_drop"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">before_drop</span><span class="p">(</span><span class="n">target</span><span class="p">,</span> <span class="n">connection</span><span class="p">,</span> <span class="o">**</span><span class="n">kw</span><span class="p">):</span>
<span class="n">dispatch</span><span class="p">(</span><span class="s">"before-drop"</span><span class="p">,</span> <span class="n">target</span><span class="p">,</span> <span class="n">connection</span><span class="p">)</span>
<span class="nd">@event.listens_for</span><span class="p">(</span><span class="n">Table</span><span class="p">,</span> <span class="s">"after_drop"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">after_drop</span><span class="p">(</span><span class="n">target</span><span class="p">,</span> <span class="n">connection</span><span class="p">,</span> <span class="o">**</span><span class="n">kw</span><span class="p">):</span>
<span class="n">dispatch</span><span class="p">(</span><span class="s">"after-drop"</span><span class="p">,</span> <span class="n">target</span><span class="p">,</span> <span class="n">connection</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">dispatch</span><span class="p">(</span><span class="n">event</span><span class="p">,</span> <span class="n">table</span><span class="p">,</span> <span class="n">bind</span><span class="p">):</span>
<span class="k">if</span> <span class="n">event</span> <span class="ow">in</span> <span class="p">(</span><span class="s">'before-create'</span><span class="p">,</span> <span class="s">'before-drop'</span><span class="p">):</span>
<span class="n">regular_cols</span> <span class="o">=</span> <span class="p">[</span><span class="n">c</span> <span class="k">for</span> <span class="n">c</span> <span class="ow">in</span> <span class="n">table</span><span class="o">.</span><span class="n">c</span> <span class="k">if</span> <span class="ow">not</span>
<span class="nb">isinstance</span><span class="p">(</span><span class="n">c</span><span class="o">.</span><span class="n">type</span><span class="p">,</span> <span class="n">Geometry</span><span class="p">)]</span>
<span class="n">gis_cols</span> <span class="o">=</span> <span class="nb">set</span><span class="p">(</span><span class="n">table</span><span class="o">.</span><span class="n">c</span><span class="p">)</span><span class="o">.</span><span class="n">difference</span><span class="p">(</span><span class="n">regular_cols</span><span class="p">)</span>
<span class="n">table</span><span class="o">.</span><span class="n">info</span><span class="p">[</span><span class="s">"_saved_columns"</span><span class="p">]</span> <span class="o">=</span> <span class="n">table</span><span class="o">.</span><span class="n">c</span>
<span class="c"># temporarily patch a set of columns not including the</span>
<span class="c"># Geometry columns</span>
<span class="n">table</span><span class="o">.</span><span class="n">columns</span> <span class="o">=</span> <span class="n">expression</span><span class="o">.</span><span class="n">ColumnCollection</span><span class="p">(</span><span class="o">*</span><span class="n">regular_cols</span><span class="p">)</span>
<span class="k">if</span> <span class="n">event</span> <span class="o">==</span> <span class="s">'before-drop'</span><span class="p">:</span>
<span class="k">for</span> <span class="n">c</span> <span class="ow">in</span> <span class="n">gis_cols</span><span class="p">:</span>
<span class="n">bind</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span>
<span class="n">select</span><span class="p">([</span>
<span class="n">func</span><span class="o">.</span><span class="n">DropGeometryColumn</span><span class="p">(</span>
<span class="s">'public'</span><span class="p">,</span> <span class="n">table</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">name</span><span class="p">)],</span>
<span class="n">autocommit</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="p">)</span>
<span class="k">elif</span> <span class="n">event</span> <span class="o">==</span> <span class="s">'after-create'</span><span class="p">:</span>
<span class="n">table</span><span class="o">.</span><span class="n">columns</span> <span class="o">=</span> <span class="n">table</span><span class="o">.</span><span class="n">info</span><span class="o">.</span><span class="n">pop</span><span class="p">(</span><span class="s">'_saved_columns'</span><span class="p">)</span>
<span class="k">for</span> <span class="n">c</span> <span class="ow">in</span> <span class="n">table</span><span class="o">.</span><span class="n">c</span><span class="p">:</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">c</span><span class="o">.</span><span class="n">type</span><span class="p">,</span> <span class="n">Geometry</span><span class="p">):</span>
<span class="n">bind</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span>
<span class="n">select</span><span class="p">([</span>
<span class="n">func</span><span class="o">.</span><span class="n">AddGeometryColumn</span><span class="p">(</span>
<span class="n">table</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">name</span><span class="p">,</span>
<span class="n">c</span><span class="o">.</span><span class="n">type</span><span class="o">.</span><span class="n">srid</span><span class="p">,</span>
<span class="n">c</span><span class="o">.</span><span class="n">type</span><span class="o">.</span><span class="n">name</span><span class="p">,</span>
<span class="n">c</span><span class="o">.</span><span class="n">type</span><span class="o">.</span><span class="n">dimension</span><span class="p">)],</span>
<span class="n">autocommit</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="p">)</span>
<span class="k">elif</span> <span class="n">event</span> <span class="o">==</span> <span class="s">'after-drop'</span><span class="p">:</span>
<span class="n">table</span><span class="o">.</span><span class="n">columns</span> <span class="o">=</span> <span class="n">table</span><span class="o">.</span><span class="n">info</span><span class="o">.</span><span class="n">pop</span><span class="p">(</span><span class="s">'_saved_columns'</span><span class="p">)</span>
<span class="n">setup_ddl_events</span><span class="p">()</span>
<span class="c"># illustrate usage</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="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</span> <span class="p">(</span><span class="n">create_engine</span><span class="p">,</span> <span class="n">MetaData</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">func</span><span class="p">,</span> <span class="n">select</span><span class="p">)</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="kn">import</span> <span class="n">sessionmaker</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.ext.declarative</span> <span class="kn">import</span> <span class="n">declarative_base</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">metadata</span> <span class="o">=</span> <span class="n">MetaData</span><span class="p">(</span><span class="n">engine</span><span class="p">)</span>
<span class="n">Base</span> <span class="o">=</span> <span class="n">declarative_base</span><span class="p">(</span><span class="n">metadata</span><span class="o">=</span><span class="n">metadata</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Road</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span>
<span class="n">__tablename__</span> <span class="o">=</span> <span class="s">'roads'</span>
<span class="n">road_id</span> <span class="o">=</span> <span class="n">Column</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">road_name</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">String</span><span class="p">)</span>
<span class="n">road_geom</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Geometry</span><span class="p">(</span><span class="mi">2</span><span class="p">))</span>
<span class="n">metadata</span><span class="o">.</span><span class="n">drop_all</span><span class="p">()</span>
<span class="n">metadata</span><span class="o">.</span><span class="n">create_all</span><span class="p">()</span>
<span class="n">session</span> <span class="o">=</span> <span class="n">sessionmaker</span><span class="p">(</span><span class="n">bind</span><span class="o">=</span><span class="n">engine</span><span class="p">)()</span>
<span class="c"># Add objects. We can use strings...</span>
<span class="n">session</span><span class="o">.</span><span class="n">add_all</span><span class="p">([</span>
<span class="n">Road</span><span class="p">(</span><span class="n">road_name</span><span class="o">=</span><span class="s">'Jeff Rd'</span><span class="p">,</span> <span class="n">road_geom</span><span class="o">=</span><span class="s">'LINESTRING(191232 243118,191108 243242)'</span><span class="p">),</span>
<span class="n">Road</span><span class="p">(</span><span class="n">road_name</span><span class="o">=</span><span class="s">'Geordie Rd'</span><span class="p">,</span> <span class="n">road_geom</span><span class="o">=</span><span class="s">'LINESTRING(189141 244158,189265 244817)'</span><span class="p">),</span>
<span class="n">Road</span><span class="p">(</span><span class="n">road_name</span><span class="o">=</span><span class="s">'Paul St'</span><span class="p">,</span> <span class="n">road_geom</span><span class="o">=</span><span class="s">'LINESTRING(192783 228138,192612 229814)'</span><span class="p">),</span>
<span class="n">Road</span><span class="p">(</span><span class="n">road_name</span><span class="o">=</span><span class="s">'Graeme Ave'</span><span class="p">,</span> <span class="n">road_geom</span><span class="o">=</span><span class="s">'LINESTRING(189412 252431,189631 259122)'</span><span class="p">),</span>
<span class="n">Road</span><span class="p">(</span><span class="n">road_name</span><span class="o">=</span><span class="s">'Phil Tce'</span><span class="p">,</span> <span class="n">road_geom</span><span class="o">=</span><span class="s">'LINESTRING(190131 224148,190871 228134)'</span><span class="p">),</span>
<span class="p">])</span>
<span class="c"># or use an explicit TextualGisElement (similar to saying func.GeomFromText())</span>
<span class="n">r</span> <span class="o">=</span> <span class="n">Road</span><span class="p">(</span><span class="n">road_name</span><span class="o">=</span><span class="s">'Dave Cres'</span><span class="p">,</span> <span class="n">road_geom</span><span class="o">=</span><span class="n">TextualGisElement</span><span class="p">(</span><span class="s">'LINESTRING(198231 263418,198213 268322)'</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</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">r</span><span class="p">)</span>
<span class="c"># pre flush, the TextualGisElement represents the string we sent.</span>
<span class="k">assert</span> <span class="nb">str</span><span class="p">(</span><span class="n">r</span><span class="o">.</span><span class="n">road_geom</span><span class="p">)</span> <span class="o">==</span> <span class="s">'LINESTRING(198231 263418,198213 268322)'</span>
<span class="n">session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="c"># after flush and/or commit, all the TextualGisElements become PersistentGisElements.</span>
<span class="k">assert</span> <span class="nb">str</span><span class="p">(</span><span class="n">r</span><span class="o">.</span><span class="n">road_geom</span><span class="p">)</span> <span class="o">==</span> <span class="s">"LINESTRING(198231 263418,198213 268322)"</span>
<span class="n">r1</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Road</span><span class="p">)</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">Road</span><span class="o">.</span><span class="n">road_name</span> <span class="o">==</span> <span class="s">'Graeme Ave'</span><span class="p">)</span><span class="o">.</span><span class="n">one</span><span class="p">()</span>
<span class="c"># illustrate the overridden __eq__() operator.</span>
<span class="c"># strings come in as TextualGisElements</span>
<span class="n">r2</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Road</span><span class="p">)</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">Road</span><span class="o">.</span><span class="n">road_geom</span> <span class="o">==</span> <span class="s">'LINESTRING(189412 252431,189631 259122)'</span><span class="p">)</span><span class="o">.</span><span class="n">one</span><span class="p">()</span>
<span class="n">r3</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Road</span><span class="p">)</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">Road</span><span class="o">.</span><span class="n">road_geom</span> <span class="o">==</span> <span class="n">r1</span><span class="o">.</span><span class="n">road_geom</span><span class="p">)</span><span class="o">.</span><span class="n">one</span><span class="p">()</span>
<span class="k">assert</span> <span class="n">r1</span> <span class="ow">is</span> <span class="n">r2</span> <span class="ow">is</span> <span class="n">r3</span>
<span class="c"># core usage just fine:</span>
<span class="n">road_table</span> <span class="o">=</span> <span class="n">Road</span><span class="o">.</span><span class="n">__table__</span>
<span class="n">stmt</span> <span class="o">=</span> <span class="n">select</span><span class="p">([</span><span class="n">road_table</span><span class="p">])</span><span class="o">.</span><span class="n">where</span><span class="p">(</span><span class="n">road_table</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">road_geom</span><span class="o">.</span><span class="n">intersects</span><span class="p">(</span><span class="n">r1</span><span class="o">.</span><span class="n">road_geom</span><span class="p">))</span>
<span class="k">print</span><span class="p">(</span><span class="n">session</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="n">stmt</span><span class="p">)</span><span class="o">.</span><span class="n">fetchall</span><span class="p">())</span>
<span class="c"># TODO: for some reason the auto-generated labels have the internal replacement</span>
<span class="c"># strings exposed, even though PG doesn't complain</span>
<span class="c"># look up the hex binary version, using SQLAlchemy casts</span>
<span class="n">as_binary</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">select</span><span class="p">([</span><span class="n">type_coerce</span><span class="p">(</span><span class="n">r</span><span class="o">.</span><span class="n">road_geom</span><span class="p">,</span> <span class="n">Geometry</span><span class="p">(</span><span class="n">coerce_</span><span class="o">=</span><span class="s">"binary"</span><span class="p">))]))</span>
<span class="k">assert</span> <span class="n">as_binary</span><span class="o">.</span><span class="n">as_hex</span> <span class="o">==</span> \
<span class="s">'01020000000200000000000000b832084100000000e813104100000000283208410000000088601041'</span>
<span class="c"># back again, same method !</span>
<span class="n">as_text</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">select</span><span class="p">([</span><span class="n">type_coerce</span><span class="p">(</span><span class="n">as_binary</span><span class="p">,</span> <span class="n">Geometry</span><span class="p">(</span><span class="n">coerce_</span><span class="o">=</span><span class="s">"text"</span><span class="p">))]))</span>
<span class="k">assert</span> <span class="n">as_text</span><span class="o">.</span><span class="n">desc</span> <span class="o">==</span> <span class="s">"LINESTRING(198231 263418,198213 268322)"</span>
<span class="n">session</span><span class="o">.</span><span class="n">rollback</span><span class="p">()</span>
<span class="n">metadata</span><span class="o">.</span><span class="n">drop_all</span><span class="p">()</span></pre></div>
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