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| <div class="section" id="secondary-indexes"> |
| <span id="id1"></span><h1>Secondary Indexes<a class="headerlink" href="#secondary-indexes" title="Permalink to this headline">¶</a></h1> |
| <p>CQL supports creating secondary indexes on tables, allowing queries on the table to use those indexes. A secondary index |
| is identified by a name defined by:</p> |
| <pre> |
| <strong id="grammar-token-index-name">index_name</strong> ::= re('[a-zA-Z_0-9]+') |
| </pre> |
| <div class="section" id="create-index"> |
| <span id="create-index-statement"></span><h2>CREATE INDEX<a class="headerlink" href="#create-index" title="Permalink to this headline">¶</a></h2> |
| <p>Creating a secondary index on a table uses the <code class="docutils literal notranslate"><span class="pre">CREATE</span> <span class="pre">INDEX</span></code> statement:</p> |
| <pre> |
| <strong id="grammar-token-create-index-statement">create_index_statement</strong> ::= CREATE [ CUSTOM ] INDEX [ IF NOT EXISTS ] [ <a class="reference internal" href="#grammar-token-index-name"><code class="xref docutils literal notranslate"><span class="pre">index_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> '(' <a class="reference internal" href="#grammar-token-index-identifier"><code class="xref docutils literal notranslate"><span class="pre">index_identifier</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> [ WITH OPTIONS = <a class="reference internal" href="types.html#grammar-token-map-literal"><code class="xref docutils literal notranslate"><span class="pre">map_literal</span></code></a> ] ] |
| <strong id="grammar-token-index-identifier">index_identifier </strong> ::= <a class="reference internal" href="ddl.html#grammar-token-column-name"><code class="xref docutils literal notranslate"><span class="pre">column_name</span></code></a> |
| | ( KEYS | VALUES | ENTRIES | FULL ) '(' <a class="reference internal" href="ddl.html#grammar-token-column-name"><code class="xref docutils literal notranslate"><span class="pre">column_name</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">INDEX</span> <span class="n">userIndex</span> <span class="k">ON</span> <span class="n">NerdMovies</span> <span class="p">(</span><span class="k">user</span><span class="p">);</span> |
| <span class="k">CREATE</span> <span class="k">INDEX</span> <span class="k">ON</span> <span class="n">Mutants</span> <span class="p">(</span><span class="n">abilityId</span><span class="p">);</span> |
| <span class="k">CREATE</span> <span class="k">INDEX</span> <span class="k">ON</span> <span class="k">users</span> <span class="p">(</span><span class="k">keys</span><span class="p">(</span><span class="n">favs</span><span class="p">));</span> |
| <span class="k">CREATE</span> <span class="k">CUSTOM</span> <span class="k">INDEX</span> <span class="k">ON</span> <span class="k">users</span> <span class="p">(</span><span class="n">email</span><span class="p">)</span> <span class="k">USING</span> <span class="s1">'path.to.the.IndexClass'</span><span class="p">;</span> |
| <span class="k">CREATE</span> <span class="k">CUSTOM</span> <span class="k">INDEX</span> <span class="k">ON</span> <span class="k">users</span> <span class="p">(</span><span class="n">email</span><span class="p">)</span> <span class="k">USING</span> <span class="s1">'path.to.the.IndexClass'</span> <span class="k">WITH</span> <span class="k">OPTIONS</span> <span class="o">=</span> <span class="p">{</span><span class="s1">'storage'</span><span class="p">:</span> <span class="s1">'/mnt/ssd/indexes/'</span><span class="p">};</span> |
| </pre></div> |
| </div> |
| <p>The <code class="docutils literal notranslate"><span class="pre">CREATE</span> <span class="pre">INDEX</span></code> statement is used to create a new (automatic) secondary index for a given (existing) column in a |
| given table. A name for the index itself can be specified before the <code class="docutils literal notranslate"><span class="pre">ON</span></code> keyword, if desired. If data already exists |
| for the column, it will be indexed asynchronously. After the index is created, new data for the column is indexed |
| automatically at insertion time.</p> |
| <p>Attempting to create an already existing index will return an error unless the <code class="docutils literal notranslate"><span class="pre">IF</span> <span class="pre">NOT</span> <span class="pre">EXISTS</span></code> option is used. If it |
| is used, the statement will be a no-op if the index already exists.</p> |
| <div class="section" id="indexes-on-map-keys"> |
| <h3>Indexes on Map Keys<a class="headerlink" href="#indexes-on-map-keys" title="Permalink to this headline">¶</a></h3> |
| <p>When creating an index on a <a class="reference internal" href="types.html#maps"><span class="std std-ref">maps</span></a>, you may index either the keys or the values. If the column identifier is |
| placed within the <code class="docutils literal notranslate"><span class="pre">keys()</span></code> function, the index will be on the map keys, allowing you to use <code class="docutils literal notranslate"><span class="pre">CONTAINS</span> <span class="pre">KEY</span></code> in |
| <code class="docutils literal notranslate"><span class="pre">WHERE</span></code> clauses. Otherwise, the index will be on the map values.</p> |
| </div> |
| </div> |
| <div class="section" id="drop-index"> |
| <span id="drop-index-statement"></span><h2>DROP INDEX<a class="headerlink" href="#drop-index" title="Permalink to this headline">¶</a></h2> |
| <p>Dropping a secondary index uses the <code class="docutils literal notranslate"><span class="pre">DROP</span> <span class="pre">INDEX</span></code> statement:</p> |
| <pre> |
| <strong id="grammar-token-drop-index-statement">drop_index_statement</strong> ::= DROP INDEX [ IF EXISTS ] <a class="reference internal" href="#grammar-token-index-name"><code class="xref docutils literal notranslate"><span class="pre">index_name</span></code></a> |
| </pre> |
| <p>The <code class="docutils literal notranslate"><span class="pre">DROP</span> <span class="pre">INDEX</span></code> statement is used to drop an existing secondary index. The argument of the statement is the index |
| name, which may optionally specify the keyspace of the index.</p> |
| <p>If the index does not exists, the statement will return an error, unless <code class="docutils literal notranslate"><span class="pre">IF</span> <span class="pre">EXISTS</span></code> is used in which case the |
| operation is a no-op.</p> |
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