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<!DOCTYPE html>
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<title>Using CQL with legacy column families - Das Keyboard Shredder</title>
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<meta name="description" content="We use Cassandra extensively at work, and up till recently we’ve been using mostly Cassandra 1.2 with Astyanax and Thrift protocol in Java applications. Very recently we started adopting Cassandra 2.0 with CQL, DataStax Java Driver and binary protocol. While one should move to CQL schema to take full advantage of the new protocol and storage engine, it’s still possible to use CQL and the new driver on existing clusters. Say we have a legacy column family with UTF8Type for row/column keys and BytesType for values, it would look like this in cassandra-cli: create column family data with column_type = 'Standard' and comparator = 'UTF8Type' and default_validation_class = 'BytesType' and key_validation_class = 'UTF8Type'; And this in cqlsh after setting start_native_transport: true in cassandra.yaml: CREATE TABLE data ( key text, column1 text, value blob, PRIMARY KEY (key, column1) ) WITH COMPACT STORAGE; In this table, key and column1 corresponds to row and column keys in the legacy column family and value corresponds to column value. Queries to look up a column value, an entire row, and selected columns in a row would look like this: SELECT value FROM mykeyspace.data WHERE key = 'rowkey' AND column1 = 'colkey'; SELECT column1, value FROM mykeyspace …" />
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<meta property="og:description" content="We use Cassandra extensively at work, and up till recently we’ve been using mostly Cassandra 1.2 with Astyanax and Thrift protocol in Java applications. Very recently we started adopting Cassandra 2.0 with CQL, DataStax Java Driver and binary protocol. While one should move to CQL schema to take full advantage of the new protocol and storage engine, it’s still possible to use CQL and the new driver on existing clusters. Say we have a legacy column family with UTF8Type for row/column keys and BytesType for values, it would look like this in cassandra-cli: create column family data with column_type = 'Standard' and comparator = 'UTF8Type' and default_validation_class = 'BytesType' and key_validation_class = 'UTF8Type'; And this in cqlsh after setting start_native_transport: true in cassandra.yaml: CREATE TABLE data ( key text, column1 text, value blob, PRIMARY KEY (key, column1) ) WITH COMPACT STORAGE; In this table, key and column1 corresponds to row and column keys in the legacy column family and value corresponds to column value. Queries to look up a column value, an entire row, and selected columns in a row would look like this: SELECT value FROM mykeyspace.data WHERE key = 'rowkey' AND column1 = 'colkey'; SELECT column1, value FROM mykeyspace …"/>
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Using <span class="caps">CQL</span> with legacy column families
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<i class="fa fa-calendar"></i><time datetime="2014-09-13T20:47:00-04:00"> Sat 13 September 2014</time>
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<p>We use <a href="http://cassandra.apache.org/">Cassandra</a> extensively <a href="http://www.slideshare.net/JimmyMrdell/playlists-at-spotify-cassandra-summit-london-2013?related=1">at work</a>, and up till recently we’ve been using mostly Cassandra 1.2 with <a href="https://github.com/Netflix/astyanax">Astyanax</a> and <a href="https://thrift.apache.org/">Thrift</a> protocol in Java applications. Very recently we started adopting Cassandra 2.0 with <span class="caps">CQL</span>, <a href="https://github.com/datastax/java-driver">DataStax Java Driver</a> and binary protocol.</p>
<p>While one should move to <span class="caps">CQL</span> schema to take full advantage of the new protocol and storage engine, it’s still possible to use <span class="caps">CQL</span> and the new driver on existing clusters. Say we have a legacy column family with <code>UTF8Type</code> for row/column keys and <code>BytesType</code> for values, it would look like this in <code>cassandra-cli</code>:</p>
<div class="highlight"><pre><span></span><span class="k">create</span> <span class="k">column</span> <span class="n">family</span> <span class="k">data</span>
<span class="k">with</span> <span class="n">column_type</span> <span class="o">=</span> <span class="s1">'Standard'</span>
<span class="k">and</span> <span class="n">comparator</span> <span class="o">=</span> <span class="s1">'UTF8Type'</span>
<span class="k">and</span> <span class="n">default_validation_class</span> <span class="o">=</span> <span class="s1">'BytesType'</span>
<span class="k">and</span> <span class="n">key_validation_class</span> <span class="o">=</span> <span class="s1">'UTF8Type'</span><span class="p">;</span>
</pre></div>
<p>And this in <code>cqlsh</code> after setting <code>start_native_transport: true</code> in <code>cassandra.yaml</code>:</p>
<div class="highlight"><pre><span></span><span class="k">CREATE</span> <span class="k">TABLE</span> <span class="k">data</span> <span class="p">(</span>
<span class="k">key</span> <span class="nb">text</span><span class="p">,</span>
<span class="n">column1</span> <span class="nb">text</span><span class="p">,</span>
<span class="n">value</span> <span class="nb">blob</span><span class="p">,</span>
<span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">(</span><span class="k">key</span><span class="p">,</span> <span class="n">column1</span><span class="p">)</span>
<span class="p">)</span> <span class="k">WITH</span> <span class="n">COMPACT</span> <span class="k">STORAGE</span><span class="p">;</span>
</pre></div>
<p>In this table, <code>key</code> and <code>column1</code> corresponds to row and column keys in the legacy column family and <code>value</code> corresponds to column value.</p>
<p>Queries to look up a column value, an entire row, and selected columns in a row would look like this:</p>
<div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">value</span> <span class="k">FROM</span> <span class="n">mykeyspace</span><span class="p">.</span><span class="k">data</span> <span class="k">WHERE</span> <span class="k">key</span> <span class="o">=</span> <span class="s1">'rowkey'</span> <span class="k">AND</span> <span class="n">column1</span> <span class="o">=</span> <span class="s1">'colkey'</span><span class="p">;</span>
<span class="k">SELECT</span> <span class="n">column1</span><span class="p">,</span> <span class="n">value</span> <span class="k">FROM</span> <span class="n">mykeyspace</span><span class="p">.</span><span class="k">data</span> <span class="k">WHERE</span> <span class="k">key</span> <span class="o">=</span> <span class="s1">'rowkey'</span><span class="p">;</span>
<span class="k">SELECT</span> <span class="n">column1</span><span class="p">,</span> <span class="n">value</span> <span class="k">FROM</span> <span class="n">mykeyspace</span><span class="p">.</span><span class="k">data</span> <span class="k">WHERE</span> <span class="k">key</span> <span class="o">=</span> <span class="s1">'rowkey'</span> <span class="k">AND</span> <span class="n">column1</span> <span class="k">IN</span> <span class="p">(</span><span class="s1">'colkey1'</span><span class="p">,</span> <span class="s1">'colkey2'</span><span class="p">);</span>
</pre></div>
<p>And I found <a href="http://www.slideshare.net/DataStax/understanding-how-cql3-maps-to-cassandras-internal-data-structure">these slides</a> that explain the mapping bewteen <span class="caps">CQL</span> and Cassandra’s storage model.</p>
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