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| <div class="section" id="triggers"> |
| <span id="cql-triggers"></span><h1>Triggers<a class="headerlink" href="#triggers" title="Permalink to this headline">¶</a></h1> |
| <p>Triggers are identified by a name defined by:</p> |
| <pre> |
| <strong id="grammar-token-trigger-name">trigger_name</strong> ::= <a class="reference internal" href="definitions.html#grammar-token-identifier"><code class="xref docutils literal notranslate"><span class="pre">identifier</span></code></a> |
| </pre> |
| <div class="section" id="create-trigger"> |
| <span id="create-trigger-statement"></span><h2>CREATE TRIGGER<a class="headerlink" href="#create-trigger" title="Permalink to this headline">¶</a></h2> |
| <p>Creating a new trigger uses the <code class="docutils literal notranslate"><span class="pre">CREATE</span> <span class="pre">TRIGGER</span></code> statement:</p> |
| <pre> |
| <strong id="grammar-token-create-trigger-statement">create_trigger_statement</strong> ::= CREATE TRIGGER [ IF NOT EXISTS ] <a class="reference internal" href="#grammar-token-trigger-name"><code class="xref docutils literal notranslate"><span class="pre">trigger_name</span></code></a> |
| ON <a class="reference internal" href="ddl.html#grammar-token-table-name"><code class="xref docutils literal notranslate"><span class="pre">table_name</span></code></a> |
| USING <a class="reference internal" href="definitions.html#grammar-token-string"><code class="xref docutils literal notranslate"><span class="pre">string</span></code></a> |
| </pre> |
| <p>For instance:</p> |
| <div class="highlight-cql notranslate"><div class="highlight"><pre><span></span><span class="k">CREATE</span> <span class="k">TRIGGER</span> <span class="n">myTrigger</span> <span class="k">ON</span> <span class="n">myTable</span> <span class="k">USING</span> <span class="s1">'org.apache.cassandra.triggers.InvertedIndex'</span><span class="p">;</span> |
| </pre></div> |
| </div> |
| <p>The actual logic that makes up the trigger can be written in any Java (JVM) language and exists outside the database. |
| You place the trigger code in a <code class="docutils literal notranslate"><span class="pre">lib/triggers</span></code> subdirectory of the Cassandra installation directory, it loads during |
| cluster startup, and exists on every node that participates in a cluster. The trigger defined on a table fires before a |
| requested DML statement occurs, which ensures the atomicity of the transaction.</p> |
| </div> |
| <div class="section" id="drop-trigger"> |
| <span id="drop-trigger-statement"></span><h2>DROP TRIGGER<a class="headerlink" href="#drop-trigger" title="Permalink to this headline">¶</a></h2> |
| <p>Dropping a trigger uses the <code class="docutils literal notranslate"><span class="pre">DROP</span> <span class="pre">TRIGGER</span></code> statement:</p> |
| <pre> |
| <strong id="grammar-token-drop-trigger-statement">drop_trigger_statement</strong> ::= DROP TRIGGER [ IF EXISTS ] <a class="reference internal" href="#grammar-token-trigger-name"><code class="xref docutils literal notranslate"><span class="pre">trigger_name</span></code></a> ON <a class="reference internal" href="ddl.html#grammar-token-table-name"><code class="xref docutils literal notranslate"><span class="pre">table_name</span></code></a> |
| </pre> |
| <p>For instance:</p> |
| <div class="highlight-cql notranslate"><div class="highlight"><pre><span></span><span class="k">DROP</span> <span class="k">TRIGGER</span> <span class="n">myTrigger</span> <span class="k">ON</span> <span class="n">myTable</span><span class="p">;</span> |
| </pre></div> |
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