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<h1>SQLAlchemy 0.9 Documentation</h1>
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<h1>Source code for examples.dogpile_caching.helloworld</h1><div class="highlight"><pre>
<span class="sd">"""helloworld.py</span>
<span class="sd">Illustrate how to load some data, and cache the results.</span>
<span class="sd">"""</span>
<span class="kn">from</span> <span class="nn">.environment</span> <span class="kn">import</span> <span class="n">Session</span>
<span class="kn">from</span> <span class="nn">.model</span> <span class="kn">import</span> <span class="n">Person</span>
<span class="kn">from</span> <span class="nn">.caching_query</span> <span class="kn">import</span> <span class="n">FromCache</span>
<span class="c"># load Person objects. cache the result in the "default" cache region</span>
<span class="k">print</span><span class="p">(</span><span class="s">"loading people...."</span><span class="p">)</span>
<span class="n">people</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">Person</span><span class="p">)</span><span class="o">.</span><span class="n">options</span><span class="p">(</span><span class="n">FromCache</span><span class="p">(</span><span class="s">"default"</span><span class="p">))</span><span class="o">.</span><span class="n">all</span><span class="p">()</span>
<span class="c"># remove the Session. next query starts from scratch.</span>
<span class="n">Session</span><span class="o">.</span><span class="n">remove</span><span class="p">()</span>
<span class="c"># load again, using the same FromCache option. now they're cached,</span>
<span class="c"># so no SQL is emitted.</span>
<span class="k">print</span><span class="p">(</span><span class="s">"loading people....again!"</span><span class="p">)</span>
<span class="n">people</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">Person</span><span class="p">)</span><span class="o">.</span><span class="n">options</span><span class="p">(</span><span class="n">FromCache</span><span class="p">(</span><span class="s">"default"</span><span class="p">))</span><span class="o">.</span><span class="n">all</span><span class="p">()</span>
<span class="c"># Specifying a different query produces a different cache key, so</span>
<span class="c"># these results are independently cached.</span>
<span class="k">print</span><span class="p">(</span><span class="s">"loading people two through twelve"</span><span class="p">)</span>
<span class="n">people_two_through_twelve</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">Person</span><span class="p">)</span><span class="o">.</span>\
<span class="n">options</span><span class="p">(</span><span class="n">FromCache</span><span class="p">(</span><span class="s">"default"</span><span class="p">))</span><span class="o">.</span>\
<span class="nb">filter</span><span class="p">(</span><span class="n">Person</span><span class="o">.</span><span class="n">name</span><span class="o">.</span><span class="n">between</span><span class="p">(</span><span class="s">"person 02"</span><span class="p">,</span> <span class="s">"person 12"</span><span class="p">))</span><span class="o">.</span>\
<span class="nb">all</span><span class="p">()</span>
<span class="c"># the data is cached under string structure of the SQL statement, *plus*</span>
<span class="c"># the bind parameters of the query. So this query, having</span>
<span class="c"># different literal parameters under "Person.name.between()" than the</span>
<span class="c"># previous one, issues new SQL...</span>
<span class="k">print</span><span class="p">(</span><span class="s">"loading people five through fifteen"</span><span class="p">)</span>
<span class="n">people_five_through_fifteen</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">Person</span><span class="p">)</span><span class="o">.</span>\
<span class="n">options</span><span class="p">(</span><span class="n">FromCache</span><span class="p">(</span><span class="s">"default"</span><span class="p">))</span><span class="o">.</span>\
<span class="nb">filter</span><span class="p">(</span><span class="n">Person</span><span class="o">.</span><span class="n">name</span><span class="o">.</span><span class="n">between</span><span class="p">(</span><span class="s">"person 05"</span><span class="p">,</span> <span class="s">"person 15"</span><span class="p">))</span><span class="o">.</span>\
<span class="nb">all</span><span class="p">()</span>
<span class="c"># ... but using the same params as are already cached, no SQL</span>
<span class="k">print</span><span class="p">(</span><span class="s">"loading people two through twelve...again!"</span><span class="p">)</span>
<span class="n">people_two_through_twelve</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">Person</span><span class="p">)</span><span class="o">.</span>\
<span class="n">options</span><span class="p">(</span><span class="n">FromCache</span><span class="p">(</span><span class="s">"default"</span><span class="p">))</span><span class="o">.</span>\
<span class="nb">filter</span><span class="p">(</span><span class="n">Person</span><span class="o">.</span><span class="n">name</span><span class="o">.</span><span class="n">between</span><span class="p">(</span><span class="s">"person 02"</span><span class="p">,</span> <span class="s">"person 12"</span><span class="p">))</span><span class="o">.</span>\
<span class="nb">all</span><span class="p">()</span>
<span class="c"># invalidate the cache for the three queries we've done. Recreate</span>
<span class="c"># each Query, which includes at the very least the same FromCache,</span>
<span class="c"># same list of objects to be loaded, and the same parameters in the</span>
<span class="c"># same order, then call invalidate().</span>
<span class="k">print</span><span class="p">(</span><span class="s">"invalidating everything"</span><span class="p">)</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">FromCache</span><span class="p">(</span><span class="s">"default"</span><span class="p">))</span><span class="o">.</span><span class="n">invalidate</span><span class="p">()</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">FromCache</span><span class="p">(</span><span class="s">"default"</span><span class="p">))</span><span class="o">.</span>\
<span class="nb">filter</span><span class="p">(</span><span class="n">Person</span><span class="o">.</span><span class="n">name</span><span class="o">.</span><span class="n">between</span><span class="p">(</span><span class="s">"person 02"</span><span class="p">,</span> <span class="s">"person 12"</span><span class="p">))</span><span class="o">.</span><span class="n">invalidate</span><span class="p">()</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">FromCache</span><span class="p">(</span><span class="s">"default"</span><span class="p">,</span> <span class="s">"people_on_range"</span><span class="p">))</span><span class="o">.</span>\
<span class="nb">filter</span><span class="p">(</span><span class="n">Person</span><span class="o">.</span><span class="n">name</span><span class="o">.</span><span class="n">between</span><span class="p">(</span><span class="s">"person 05"</span><span class="p">,</span> <span class="s">"person 15"</span><span class="p">))</span><span class="o">.</span><span class="n">invalidate</span><span class="p">()</span></pre></div>
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