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examples.dogpile_caching.relationship_caching
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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.dogpile_caching.relationship_caching</h1><div class="highlight"><pre>
<span></span><span class="sd">"""Illustrates how to add cache options on</span>
<span class="sd">relationship endpoints, so that lazyloads load from cache.</span>
<span class="sd">Load a set of Person and Address objects, specifying that</span>
<span class="sd">related PostalCode, City, Country objects should be pulled from long</span>
<span class="sd">term cache.</span>
<span class="sd">"""</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="k">import</span> <span class="n">joinedload</span>
<span class="kn">from</span> <span class="nn">.environment</span> <span class="k">import</span> <span class="n">root</span>
<span class="kn">from</span> <span class="nn">.environment</span> <span class="k">import</span> <span class="n">Session</span>
<span class="kn">from</span> <span class="nn">.model</span> <span class="k">import</span> <span class="n">cache_address_bits</span>
<span class="kn">from</span> <span class="nn">.model</span> <span class="k">import</span> <span class="n">Person</span>
<span class="k">for</span> <span class="n">p</span> <span class="ow">in</span> <span class="n">Session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Person</span><span class="p">)</span><span class="o">.</span><span class="n">options</span><span class="p">(</span>
<span class="n">joinedload</span><span class="p">(</span><span class="n">Person</span><span class="o">.</span><span class="n">addresses</span><span class="p">),</span> <span class="n">cache_address_bits</span>
<span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">format_full</span><span class="p">())</span>
<span class="nb">print</span><span class="p">(</span>
<span class="s2">"</span><span class="se">\n\n</span><span class="s2">If this was the first run of relationship_caching.py, "</span>
<span class="s2">"SQL was likely emitted to "</span>
<span class="s2">"load postal codes, cities, countries.</span><span class="se">\n</span><span class="s2">"</span>
<span class="s2">"If run a second time, assuming the cache is still valid, "</span>
<span class="s2">"only a single SQL statement will run - all "</span>
<span class="s2">"related data is pulled from cache.</span><span class="se">\n</span><span class="s2">"</span>
<span class="s2">"To clear the cache, delete the file </span><span class="si">%r</span><span class="s2">. </span><span class="se">\n</span><span class="s2">"</span>
<span class="s2">"This will cause a re-load of cities, postal codes and countries on "</span>
<span class="s2">"the next run.</span><span class="se">\n</span><span class="s2">"</span> <span class="o">%</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="s2">"cache.dbm"</span><span class="p">)</span>
<span class="p">)</span></pre></div>
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