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<h1>Object Mapper<a class="headerlink" href="#object-mapper" title="Permalink to this headline">¶</a></h1>
<p>cqlengine is the Cassandra CQL 3 Object Mapper packaged with this driver</p>
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<dd>Examples defining models, and mapping them to tables</dd>
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<dd>Overview of query sets and filtering</dd>
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<span id="id1"></span><h2>Getting Started<a class="headerlink" href="#getting-started" title="Permalink to this headline">¶</a></h2>
<blockquote>
<div><div class="highlight-python"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">uuid</span>
<span class="kn">from</span> <span class="nn">cassandra.cqlengine</span> <span class="kn">import</span> <span class="n">columns</span>
<span class="kn">from</span> <span class="nn">cassandra.cqlengine</span> <span class="kn">import</span> <span class="n">connection</span>
<span class="kn">from</span> <span class="nn">datetime</span> <span class="kn">import</span> <span class="n">datetime</span>
<span class="kn">from</span> <span class="nn">cassandra.cqlengine.management</span> <span class="kn">import</span> <span class="n">sync_table</span>
<span class="kn">from</span> <span class="nn">cassandra.cqlengine.models</span> <span class="kn">import</span> <span class="n">Model</span>
<span class="c1">#first, define a model</span>
<span class="k">class</span> <span class="nc">ExampleModel</span><span class="p">(</span><span class="n">Model</span><span class="p">):</span>
<span class="n">example_id</span> <span class="o">=</span> <span class="n">columns</span><span class="o">.</span><span class="n">UUID</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">default</span><span class="o">=</span><span class="n">uuid</span><span class="o">.</span><span class="n">uuid4</span><span class="p">)</span>
<span class="n">example_type</span> <span class="o">=</span> <span class="n">columns</span><span class="o">.</span><span class="n">Integer</span><span class="p">(</span><span class="n">index</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">created_at</span> <span class="o">=</span> <span class="n">columns</span><span class="o">.</span><span class="n">DateTime</span><span class="p">()</span>
<span class="n">description</span> <span class="o">=</span> <span class="n">columns</span><span class="o">.</span><span class="n">Text</span><span class="p">(</span><span class="n">required</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span>
<span class="c1">#next, setup the connection to your cassandra server(s)...</span>
<span class="c1"># see http://datastax.github.io/python-driver/api/cassandra/cluster.html for options</span>
<span class="c1"># the list of hosts will be passed to create a Cluster() instance</span>
<span class="n">connection</span><span class="o">.</span><span class="n">setup</span><span class="p">([</span><span class="s1">'127.0.0.1'</span><span class="p">],</span> <span class="s2">"cqlengine"</span><span class="p">,</span> <span class="n">protocol_version</span><span class="o">=</span><span class="mi">3</span><span class="p">)</span>
<span class="c1">#...and create your CQL table</span>
<span class="o">>>></span> <span class="n">sync_table</span><span class="p">(</span><span class="n">ExampleModel</span><span class="p">)</span>
<span class="c1">#now we can create some rows:</span>
<span class="o">>>></span> <span class="n">em1</span> <span class="o">=</span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">example_type</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s2">"example1"</span><span class="p">,</span> <span class="n">created_at</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="o">>>></span> <span class="n">em2</span> <span class="o">=</span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">example_type</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s2">"example2"</span><span class="p">,</span> <span class="n">created_at</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="o">>>></span> <span class="n">em3</span> <span class="o">=</span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">example_type</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s2">"example3"</span><span class="p">,</span> <span class="n">created_at</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="o">>>></span> <span class="n">em4</span> <span class="o">=</span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">example_type</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s2">"example4"</span><span class="p">,</span> <span class="n">created_at</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="o">>>></span> <span class="n">em5</span> <span class="o">=</span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">example_type</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s2">"example5"</span><span class="p">,</span> <span class="n">created_at</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="o">>>></span> <span class="n">em6</span> <span class="o">=</span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">example_type</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s2">"example6"</span><span class="p">,</span> <span class="n">created_at</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="o">>>></span> <span class="n">em7</span> <span class="o">=</span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">example_type</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s2">"example7"</span><span class="p">,</span> <span class="n">created_at</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="o">>>></span> <span class="n">em8</span> <span class="o">=</span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">example_type</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s2">"example8"</span><span class="p">,</span> <span class="n">created_at</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="c1">#and now we can run some queries against our table</span>
<span class="o">>>></span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">count</span><span class="p">()</span>
<span class="mi">8</span>
<span class="o">>>></span> <span class="n">q</span> <span class="o">=</span> <span class="n">ExampleModel</span><span class="o">.</span><span class="n">objects</span><span class="p">(</span><span class="n">example_type</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">q</span><span class="o">.</span><span class="n">count</span><span class="p">()</span>
<span class="mi">4</span>
<span class="o">>>></span> <span class="k">for</span> <span class="n">instance</span> <span class="ow">in</span> <span class="n">q</span><span class="p">:</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">instance</span><span class="o">.</span><span class="n">description</span>
<span class="n">example5</span>
<span class="n">example6</span>
<span class="n">example7</span>
<span class="n">example8</span>
<span class="c1">#here we are applying additional filtering to an existing query</span>
<span class="c1">#query objects are immutable, so calling filter returns a new</span>
<span class="c1">#query object</span>
<span class="o">>>></span> <span class="n">q2</span> <span class="o">=</span> <span class="n">q</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">example_id</span><span class="o">=</span><span class="n">em5</span><span class="o">.</span><span class="n">example_id</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">q2</span><span class="o">.</span><span class="n">count</span><span class="p">()</span>
<span class="mi">1</span>
<span class="o">>>></span> <span class="k">for</span> <span class="n">instance</span> <span class="ow">in</span> <span class="n">q2</span><span class="p">:</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">instance</span><span class="o">.</span><span class="n">description</span>
<span class="n">example5</span>
</pre></div>
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