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| <div class="subTitle">org.apache.accumulo.core.client.sample</div> |
| <h2 title="Interface Sampler" class="title">Interface Sampler</h2> |
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| <dt>All Known Implementing Classes:</dt> |
| <dd><a href="../../../../../../org/apache/accumulo/core/client/sample/AbstractHashSampler.html" title="class in org.apache.accumulo.core.client.sample">AbstractHashSampler</a>, <a href="../../../../../../org/apache/accumulo/core/client/sample/RowColumnSampler.html" title="class in org.apache.accumulo.core.client.sample">RowColumnSampler</a>, <a href="../../../../../../org/apache/accumulo/core/client/sample/RowSampler.html" title="class in org.apache.accumulo.core.client.sample">RowSampler</a></dd> |
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| <pre>public interface <span class="typeNameLabel">Sampler</span></pre> |
| <div class="block">A function that decides which key values are stored in a tables sample. As Accumuo compacts data |
| and creates rfiles it uses a Sampler to decided what to store in the rfiles sample section. The |
| class name of the Sampler and the Samplers configuration are stored in each rfile. A scan of a |
| tables sample will only succeed if all rfiles were created with the same sampler and sampler |
| configuration. |
| |
| <p> |
| Since the decisions that Sampler makes are persisted, the behavior of a Sampler for a given |
| configuration should always be the same. One way to offer a new behavior is to offer new options, |
| while still supporting old behavior with a Samplers existing options. |
| |
| <p> |
| Ideally a sampler that selects a Key k1 would also select updates for k1. For example if a |
| Sampler selects : |
| <code>row='000989' family='name' qualifier='last' visibility='ADMIN' time=9 value='Doe'</code>, it |
| would be nice if it also selected : |
| <code>row='000989' family='name' qualifier='last' visibility='ADMIN' time=20 value='Dough'</code>. |
| Using hash and modulo on the key fields is a good way to accomplish this and |
| <a href="../../../../../../org/apache/accumulo/core/client/sample/AbstractHashSampler.html" title="class in org.apache.accumulo.core.client.sample"><code>AbstractHashSampler</code></a> provides a good basis for implementation.</div> |
| <dl> |
| <dt><span class="simpleTagLabel">Since:</span></dt> |
| <dd>1.8.0</dd> |
| </dl> |
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| <td class="colFirst"><code>boolean</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/accumulo/core/client/sample/Sampler.html#accept-org.apache.accumulo.core.data.Key-">accept</a></span>(<a href="../../../../../../org/apache/accumulo/core/data/Key.html" title="class in org.apache.accumulo.core.data">Key</a> k)</code> </td> |
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| <td class="colFirst"><code>void</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/accumulo/core/client/sample/Sampler.html#init-org.apache.accumulo.core.client.sample.SamplerConfiguration-">init</a></span>(<a href="../../../../../../org/apache/accumulo/core/client/sample/SamplerConfiguration.html" title="class in org.apache.accumulo.core.client.sample">SamplerConfiguration</a> config)</code> |
| <div class="block">An implementation of Sampler must have a noarg constructor.</div> |
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| <h4>init</h4> |
| <pre>void init(<a href="../../../../../../org/apache/accumulo/core/client/sample/SamplerConfiguration.html" title="class in org.apache.accumulo.core.client.sample">SamplerConfiguration</a> config)</pre> |
| <div class="block">An implementation of Sampler must have a noarg constructor. After construction this method is |
| called once to initialize a sampler before it is used.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>config</code> - Configuration options for a sampler.</dd> |
| </dl> |
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| <h4>accept</h4> |
| <pre>boolean accept(<a href="../../../../../../org/apache/accumulo/core/data/Key.html" title="class in org.apache.accumulo.core.data">Key</a> k)</pre> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>k</code> - A key that was written to a rfile.</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>True if the key (and its associtated value) should be stored in the rfile's sample. |
| Return false if it should not be included.</dd> |
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